Passive homes - Guidelines For The Design And Construction Of Passive House Dwellings In Ireland

Passive homes - Guidelines For The Design And Construction Of Passive House Dwellings In Ireland
Passive homes
Sustainable Energy Ireland (SEI)
Sustainable Energy Ireland was established as Ireland’s national energy agency under the Sustainable Energy Act 2002. SEI’s
mission is to promote and assist the development of sustainable energy. This encompasses environmentally and economically sustainable production, supply and use of energy, in support of Government policy, across all sectors of the economy
including public bodies, the business sector, local communities and individual consumers. Its remit relates mainly to improving energy efficiency, advancing the development and competitive deployment of renewable sources of energy and
combined heat and power, and reducing the environmental impact of energy production and use, particularly in respect of
greenhouse gas emissions.
SEI is charged with implementing significant aspects of government policy on sustainable energy and the climate change
abatement, including:
Assisting deployment of superior energy technologies in each sector as required;
Raising awareness and providing information, advice and publicity on best practice;
Stimulating research, development and demonstration;
Stimulating preparation of necessary standards and codes;
Publishing statistics and projections on sustainable energy and achievement of targets.
It is funded by the Government through the National Development Plan with programmes part financed by the European
© Sustainable Energy Ireland, 2008. All rights reserved.
No part of this material may be reproduced, in whole or in part, in any form or by any means, without permission. The material contained in this publication is presented in good faith, but its application must be considered in the light of individual projects. Sustainable Energy Ireland can not be held
responsible for any effect, loss or expense resulting from the use of material presented in this publication.
Prepared by MosArt Architecture, UCD Energy Research Group and SEI Renewable Energy Information Office
Table of Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
The ‘Passive House’ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Passive House and the Passivhaus Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Definition of the Passivhaus Standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Technical Definition of the Passivhaus Standard for Ireland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Applications of the Passivhaus Standard in the EU and Ireland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Evolution of the Passivhaus Standard in Europe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Application of the Passivhaus Standard in Ireland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Dwelling Energy Assessment Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Dwelling Energy Assessment Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Compliance with the Building Regulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Building Energy Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
PHPP and DEAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
How to Design and Specify a Passive House in Ireland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Building Design Process for a Passive House . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
General Principles: Heat Energy Losses and Heat Energy Gains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Passive House Building Envelope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Passive House Building Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Energy Balance Calculations and Passive House Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
PHPP Software and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Passive House Certifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Passive House Prototype for Application in Ireland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Design and Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Combining Aesthetic and Energy Performance in House Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Decision Support using Passive House Planning Package (PHPP) Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Prototype Passive House External Wall Sections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Prototype Passive House Design including Mechanical and Electrical Services . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
Cost Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
By Dr Wolfgang Feist, Founder of the Passive House Institute, Germany
Energy Efficient Passive Houses – Reducing the Impact of Global Warming
The February 2007 report of the Inter-Governmental Panel on Climate Change
(IPCC) has shown that climate change is already a very serious global issue. The
negative effects it will have on the ecosystem, the world economy and on living
conditions are anticipated to be on a massive scale.
Climate change is caused largely by human behaviour due mainly to the use of
fossil fuels as our main source of energy generation. The magnitude of future
climate changes is closely linked to worldwide CO2 emissions into the earth’s
atmosphere. The worst effects of global warming, such as a thawing of the entire
land-borne ice in Greenland and Antarctica, can still be prevented. However, this
requires a substantial reduction in worldwide CO2 emissions far below the
current level.
There is hardly any doubt that an energy system ready for the future will have to
be sustainable. Sustainable development is economic development that can be
continued in the future without causing significant problems for other people,
the environment and future generations.
Passive Housing can play a major role in reducing the impact of global warming.
The energy requirement of a passive house is so low that a family will never again
need to worry about energy price hikes. Passive Houses are virtually independent
of fossil sources of energy and can be fully supplied with renewable energy if a
compact heat pump unit is used in combination with an ecological electricity
supplier. Due to the low energy requirement of passive houses the regionally
available renewable energy sources are sufficient to provide a constant supply of
energy for everyone.
Ireland’s mild climate puts it in a favourable position to introduce Passive Houses
to mainstream construction compared to the more severe climates prevalent in
central Europe.
Sustainable Energy Ireland is Ireland’s national energy authority, set up to support Irish government energy
policy objectives. Following the introduction of new legislation, most notably the European Community
Directive on the Energy Performance of Buildings and the recent announcement of the intent to regulate
and require the use of renewable energy systems in new buildings, we are seeing the emergence of
extraordinary standards of energy performance for building construction in Ireland, as well as a rapid
increase in the uptake of renewable energy technologies for building services.
Ireland is facing a number of serious challenges including
rising energy costs and meeting our emissions obligations
under the Kyoto protocol. These and other factors have
given rise to a fundamental rethink in the way we design,
construct and operate buildings. it is becoming clear that
building ‘green’ has evolved and is fast becoming the
preferred choice, providing high quality, high efficiency,
dynamic and cost effective solutions for consumers and
businesses. The passive house is the ultimate in low energy
building and is recognised in Europe as the most advanced
in terms of energy performance of buildings. Interestingly,
the European Commission is set on implementing more
stringent requirements for the refurbishment of existing
buildings and moving towards the passive house standard.
Today, the passive house offers one of the most desirable
technological and economical solutions for comfortable
living and working. It can be applied to new and existing
buildings in the commercial, industrial, public and residential sectors. With over 6,000 passive houses built in Europe,
this well proven and tested innovative standard is now
attracting significant interest in Ireland with pioneers like
MosArt and Scandinavian Homes leading an emerging
movement in the construction industry.
In response to the need to educate professionals and their
clients on how to design, specify and construct passive
houses and facilitate the further development of this
standard here in Ireland SEI commissioned ‘Guidelines for
the Design and Construction of Passive House Dwellings in
Ireland‘. These detailed guidelines for self-builders and
architects focus on new build houses and cover both
conventional block construction and timber frame
construction methods. They will ultimately become part of
a suite of guidelines to cover, for example, multiple
dwellings, non-residential buildings, extensions, renovations etc.
The guidelines cover the rationale and definition of the
passive house standard, how to design and specify a passive
house along with, construction options, associated services,
cost considerations and lifestyle issues. SEI hopes they will
be useful in increasing awareness and understanding of the
key principles and techniques in designing, constructing
and operating the ultimate low energy building – the
passive house.
Brendan Halligan
Chairman, Sustainable Energy Ireland
The ‘Passive House’
The ‘Passive House’
1.1 Passive House and the
Passivhaus Standard
1.1.1 Definition of the Passivhaus
A passive house1 is an energy-efficient
building with year-round comfort and
good indoor environmental conditions
without the use of significant active
space heating or cooling systems. The
space heat requirement is reduced by
means of passive measures to the point
at which there is no longer any need for a
conventional heating system; the air
supply system essentially suffices to
distribute the remaining heat requirement. A passive house provides a very
high level of thermal comfort and provision of whole-house even temperature.
The concept is based on minimising heat
losses and maximising heat gains, thus
enabling the use of simple building
services. The appearance of a passive
house does not need to differ from a
conventional house and living in it does
not require any lifestyle changes. Passive
houses are naturally well lit due to large
glazed areas designed to optimise solar
gains, as well as healthy buildings in
which to live and work due to fresh air
supply through the controlled ventilation system.
The Passivhaus Standard is a specific
construction standard for buildings with
good comfort conditions during winter
and summer, without traditional space
heating systems and without active
cooling. Typically this includes
optimised insulation levels with minimal
thermal bridges, very low air-leakage
through the building, utilisation of
passive solar and internal gains and
good indoor air quality maintained by a
mechanical ventilation system with
Renewable energy sources are used as
much as possible to meet the resulting
energy demand (Promotion of European
Passive Houses (PEP) 2006), including
that required for the provision of domestic hot water (DHW).
The Passivhaus Standard is a construction standard developed by the
Passivhaus Institut in Germany
( The standard can
be met using a variety of design strategies, construction methods and
technologies and is applicable to any
building type.
This publication outlines the requirements in applying that standard in
Ireland, and in all cases when referring to
a passive house is describing a house
built to the requirements of the
Passivhaus Standard.
It should be noted that the primary
focus in building to the Passivhaus
Standard is directed towards creating a
thermally efficient envelope which
makes optimum use of free heat gains in
order to minimise space heating requirement. While there are also limitations on
the amount of primary energy that can
be used by a dwelling for such demands
as DHW, lighting and household appliances, this will not be the primary focus
of these guidelines. That is not intended
to imply that such energy uses are
insignificant, however. In fact, a passive
house may have similar DHW requirements as would apply to any typical
house in Ireland and given the low
energy required for space heating the
energy demand for DHW will thus represent a relatively high proportion of the
overall consumption. In order to address
this, some guidance is provided on
Passive house in Ghent, Belgium (2004).
Source: Passiefhuis Platform vzw.
Passive house in Oberosterreich, Austria (2000).
Source: IG Passivhaus Osterreich Innovative Passivhaus
Interior of passive house in Oberosterreich, Austria
(2000). Source: IG Passivhaus Osterreich Innovative
Passivhaus projekte.
page 1
1. Super Insulation
Insulation Walls
Insulation Roof
Insulation Floor
Window Frames, Doors
Window Glazing
Thermal Bridges
Structural Air Tightness
2. Heat Recovery/ Air Quality
Ventilation counter flow
air to air heat exchanger
Minimal Space Heating
Passive house in Hannover, Germany (2004).
Source: IG Passivhaus Deutschland Innovative
Passivhaus projekte.
Air-leakage (or infiltration) is the
uncontrolled penetration of outside
air into a building. It takes place
through openings, primarily through
inadequate and imperfect sealing
between window frames and walls,
between the opening sections of the
windows and along the joints of the
Thermal bridging refers to a material,
or assembly of materials, in a building envelope through which heat is
transferred at a substantially higher
rate (due to higher thermal conductivity) than through the surrounding
window or door and wall, wall and
floor, and wall and roof should be
designed carefully to avoid or
minimise thermal bridging. A thermal
bridge increases heat loss through
the structure, and in some extreme
cases may cause surface condensation or interstitial condensation into
the construction. Surface mould
growth or wood rot may be the consequences of a thermal bridge.
U < 0.175 W/(m2K)
U < 0.15 W/(m2K)
U < 0.15 W/(m2K)
U < 0.8 W/(m2K)
U < 0.8 W/(m2K)
Linear heat Coefficient Ψ < 0.01 W/(m2K)
n50 < 0.6/ air changes per hour
Heat Recovery Efficiency > 75%
Efficient small capacity heating system
Air quality through ventilation rate
Ventilation Supply Ducts Insulated
DHW Pipes Insulated
Post heating ventilation air/ Low temperature
Biomass, compact unit, gas etc.
Min 0.4 ac/hr or 30m3/pers/hr
3. Passive Solar Gain
Window Glazing
Solar Orientation
Thermal Mass within Envelope
Solar energy transmittance g > 50%
Minimal glazing to north
4. Electric Efficiency
Energy Labelled Household Appliances
Hot water connection to washing
machines/ dishwashers
Compact Fluorescent or LED Lighting
Regular maintenance ventilation filters
Energy Efficient Fans/Motors
5. On-site Renewables
DHW Solar Heating
Biomass system
Wind Turbine
Other including geothermal
Area to be dictated by house size and occupancy
Application in a case by case basis
Application in a case by case basis
Application in a case by case basis
A rated appliances
Table 1. Technical Definition of the Passivhaus Standard for Ireland.
strategies to ensure that renewable
energies are employed as much as possible for production of DHW.
Structural air-tightness (reduction of air
infiltration) and minimal thermal bridging are essential. A whole-house
mechanical heat recovery ventilation
system (MHRV) is used to supply
controlled amounts of fresh air to the
house. The incoming fresh air is preheated, via a heat exchanger, by the
outgoing warm stale air. If additional
heat is required, a small efficient backup
system (using a renewable energy
source, for example a wood pellet stove)
can be used to boost the temperature of
the fresh air supplied to the house.
The energy requirement of a house built
to the Passivhaus Standard is:
Annual space heating requirement
of 15 kWh/(m2a) treated floor area
(TFA), and
page 2
Passivhaus Standard for the Prototype House
in the Irish Climate
The upper limit for total primary
energy demand for space and water
heating, ventilation, electricity for
fans and pumps, household appliances, and lighting not exceeding
120 kWh/(m2a), regardless of energy
Additionally, the air-leakage test results
must not exceed 0.6 air changes per
hour using 50 Pascal over-pressurisation
and under-pressurisation testing.
In order to maintain high comfort levels
in any building, heat losses must be
replaced by heat gains. Heat losses occur
through the building fabric due to transmission through poorly insulated walls,
floor, ceiling and glazing as well as from
uncontrolled cold air infiltration through
leaky construction and poorly fitted
windows and doors. In a typical older
dwelling, such heat losses have to be
balanced by heat gains mostly
1.1.2 Technical Definition of the
Passivhaus Standard for Ireland
Illustration of comparative heat losses and heat gains in older dwellings and in dwellings built to Passivhaus
Standard. Source: Passivhaus Institut.
kWh/m 2/y
In Table 1 a range of U-values is specified
in order to meet the Passivhaus Standard
of annual space heating requirement of
15 kWh/(m2a) for the Irish climate.
Specifying U-values is dependent upon
many variables and can only be verified
through testing the performance of the
dwelling design in the Passive House
Planning Package (PHPP) software. The
U-values included in Table 1 have been
tested for the prototype passive house
presented later in Section 3. This prototype house is a semi-detached two
storey house of compact form. A
detached bungalow house of sprawling
form would require much lower U-values
to meet the Passivhaus Standard. Due to
the mild Irish climate, it is possible to
meet the standard using U-values for
walls in the prototype house that are
higher than those typically recommended by the Passivhaus Institut for
colder central European climates.
Part L 2005
Part L 2007
Passivhaus Standard
Space heating energy comparison, Building Regulations (TGD) Part L 2005 and 2007 and the Passivhaus Standard .
Source: Sustainable Energy Ireland
contributed by a space heating system.
The internal heat gains from occupants
and other sources such as household
appliances as well as passive solar gains
contribute a relatively small proportion
of the total overall need in a conventional older dwelling. In a passive house,
the heat losses are reduced so dramatically (through better insulation and
airtight detailing) such that the same
internal gains and passive solar gain
Primary energy, in kWh/year: This
includes delivered energy, plus an
allowance for the energy “overhead”
incurred in extracting, processing and
transporting a fuel or other energy
carrier to the dwelling. For example,
in the case of electricity it takes
account of generation efficiency at
power stations. SEI, Dwelling Energy
Assessment Procedure (DEAP), 2006
version 2, pp. 28.
Delivered energy, in kWh/year: This
corresponds to the energy consumption that would normally appear on
the energy bills of the dwelling for
the assumed standardised occupancy
and end-uses considered.
now contribute a relatively high proportion of the total need. As a result of this,
a smaller space heating system is
required compared to that needed in a
conventional older dwelling.
A new built semi-detached, two storey
Irish house built to comply with the
requirements of Building Regulations
Technical Guidance Document (TGD)
Part L 2005, Conservation of Fuel and
Energy), uses approximately 75
kWh/(m2a) energy requirement for space
heating and 156 kWh/(m2a) primary
energy. The equivalent house built to the
requirements of TGD Part L 2007 would
be liable to use 40-50 kWh/(m2a) delivered / useful energy for space heating
and 90-95 kWh/(m2a) primary energy.
The Passivhaus Standard requirement for
space heating is 15kWh/(m2a). When
compared, and having regard to
constraints imposed by other requirements in the Building Regulations Part L,
a passive house thus represents a saving
of around 70% on space heating demand
relative to a typical house built to the
Building Regulations 2005, and around
60% relative to a typical house built to
the Building Regulations 2007.
A sensitivity analysis was undertaken
using different U-values for the prototype house in order to see whether it
would be possible to relax the building
fabric requirements e.g. in relation to
glazing, in Ireland and still achieve the
Passivhaus Standard. The results of this
analysis are included in Section 2.
1.2 Applications of the
Passivhaus Standard in
the EU and Ireland
1.2.1 Evolution of the Passivhaus
Standard in Europe
The Passivhaus Standard originated in
1988 by Professor Bo Adamson of the
University of Lund, Sweden and Dr.
Wolfgang Feist of the Institute for
Housing and the Environment. The
concept was developed through a
number of research projects and first
tested on a row of terraced houses by Dr.
Wolfgang Feist in 1991 in Darmstadt,
Germany. The Passivhaus Institut
( was founded in
Darmstadt, Germany in 1996 by Dr.
Wolfgang Feist as an independent
research institution. Since then, it has
been at the forefront of the Passive
House movement in Germany and has
been instrumental in disseminating the
standard throughout Europe and
page 3
Passive house in Guenzburg, Germany (2006)
Source: UCD Energy Research Group
Passive house Eusenstadt, Austria
Source: Construct Ireland Issue 2, Vol 3
Multi-family dwelling ‘ Hohe Strasse’ Hannover,
Germany Source: UCD Energy Research Group
overseas. The Institut provides a number
of services including: "Passivhaus
Projektierungs Paket" (PHPP - Passive
House Planning Package), a worksheet
used to determine the energy supply /
demand balance for passive buildings
(available in Ireland from SEI Renewable
email:[email protected]); consultancy
design of passive buildings and building
components; and certification of quality
approved passive houses (more details
in Section 2).
Over 6,000 dwellings built to the
Passivhaus Standard have been
constructed all over Europe in recent
years. This includes 4,000 in Germany
and Austria,2 where the Passivhaus
Standard was first applied as well as
Norway, Sweden, Denmark and Belgium
and numbers are continuing to grow.
CEPHEUS3 (Cost Efficient Passive Houses
as European Standards) was a research
project (1998-2001) that assessed and
validated the Passivhaus Standard on a
wider European scale. The project was
sponsored by the European Union as
part of the THERMIE Programme of the
European Commission, DirectorateGeneral of Transport and Energy. Under
CEPHEUS, 14 housing developments
were built, resulting in a total of 221
homes constructed to the Passivhaus
Standard in five European countries.
Another project supported by the
European Commission Directorate
General for Energy and Transport is PEP,
which stands for ‘Promotion of European
Passive Houses’ (http://www.european PEP is a consortium
of European partners aiming to spread
the knowledge and experience on the
passive house concept throughout the
professional building community,
beyond the select group of specialists.
1.2.2 Application of Passivhaus
Standard in Ireland
Kronsberg Passivhaus Complex Hannover,
Source: UCD Energy Reseach Group
page 4
The Kyoto Protocol was ratified in 2005
and the proposed targets of reducing
greenhouse gas (principally CO2)
emissions by 8% compared to 1990
levels by the period 2008-2012 became
legally binding for EU Member States
(UNFCCC, 1997). Within the EU burden
sharing agreement in this regard,
Ireland's target limit of 13% above 1990
levels had been reached in 1997, and it is
likely that the limit will be overshot by
up to 37% (74Mt CO2) by 2010 (O’Leary
et al, 2005). The EC Green Paper on
Energy Efficiency (EU, 2005), states that it
is possible for the EU-25 Member States
to achieve energy savings of 20% by
2010, and sees the greatest proportion
of these savings (32%) coming from the
built environment.
In Ireland the residential sector accounts
for 25% of primary energy consumption
and energy related CO2 emissions
(11,896 kt CO2), the second largest
sector after transport at 35%. The
average dwelling is responsible for
approximately 8.1 tonnes of CO2
emissions, 4.8 tonnes from direct fuel
use and 3.3 tonnes from electricity use.
Irish dwellings have a higher average
level of fuel, electricity and energy
related CO2 emissions per dwelling
compared to the average of the EU-15
(SEI, 2008).
Following the Government White Paper
‘Delivering a Sustainable Energy Future
for Ireland’ (DCMNR, 2007), and the
subsequent Programme for Government, the Building Regulations Part L in
respect of new dwellings have been
strengthened to bring a 40% reduction
relative to previous standards in respect
of primary energy consumption and
associated CO2 emissions arising from
space heating, water heating, ventilation, associated pumps and fans, and
lighting energy usage. These provisions
apply from July 2008. This policy has
committed to a further review in 2010
with the aim of extending that improvement to 60%.
It is clear that the performance of both
new build and existing housing stock
must be addressed if we are to achieve
the objectives set out both at European
and national level. The energy requirement of a house built to Passivhaus
Standard goes beyond the 40%
improvement that applies from July
The Passivhaus Standard was first introduced in Ireland by the Swedish architect Hans Eek at the ‘See the Light’
conference organised by Sustainable
Energy Ireland (SEI) in June 2002. Tomás
O’Leary of MosArt Architects, a delegate
at the conference, was so enthused by
Mr Eek’s presentation that he decided on
the spot to sell his townhouse, buy a site
in the countryside in Co. Wicklow and
build a passive house. The O’Leary family
has been living in the “Out of the Blue”
house since Spring 2005. This house is
the first Irish passive house to be certified by the Passivhaus Institut in
Germany, and has been the focus of a
research, demonstration and energy
monitoring project funded by SEI.
MosArt Architects, the Passivhaus
Institute of Dr Wolfgang Feist and the
UCD Energy Research Group are
partners in the project. The project has
been instrumental in establishing the
basis for the deployment of the
Passivhaus Standard in Ireland in different ways:
The EU Energy Performance of Buildings Directive (EPBD) was transposed into Irish
law on 4th January 2006. This states that when a building is constructed, rented or
sold a Building Energy Rating (BER) certificate and label must be made available to
prospective buyers or tenants. The BER is expressed in terms of KWh of primary
energy/m2/year. A passive house has the potential to achieve an A2 or even an A1
rating as shall be demonstrated in Section 3(MosArt).
it has provided a learning experience
for professionals involved in the
design, specification, construction
and servicing stages
it will provide a scientific basis for
performance assessment through
monitoring and evaluation
it is an excellent demonstration tool
and has been the focus of many
visits, presentations and journal
1.3 Dwelling Energy
Assessment Procedure
1.3.1 Dwelling Energy Assessment
The Dwelling Energy Assessment
Procedure (DEAP) is the Irish official
procedure for calculating and assessing
the energy performance of dwellings.
The procedure takes account of the
energy required for space heating,
ventilation, water heating, associated
pumps and fans, and lighting, less
savings from energy generation
technologies. The DEAP calculations are
based on standardised occupancy and
the procedure determines annual
values for delivered energy consumption, primary energy consumption, CO2
emissions and costs. These values are
expressed both in terms of annual totals
and per square metre of total floor area
of the dwelling.
As the national methodology, DEAP
serves two primary functions. The first is
Building Energy Rating Label. Source: Sustainable Energy Ireland.
to demonstrate compliance with certain
provisions in the Building Regulations
and the second is to produce a Building
Energy Rating for a dwelling.
1.3.2 Compliance with the Building
The DEAP methodology is used to
demonstrate compliance with certain
aspects of Part L of the Irish Building
Regulations (The Conservation of Fuel
and Energy - Dwellings: 2007). In partic-
ular, it is used to calculate the primary
energy consumption associated with
the space heating and ventilation, water
heating, associated pumps and fans, and
lighting requirements of a dwelling and
to determine the amount of CO2
emissions associated with this energy
If both the energy consumption and the
CO2 emissions are below the limits set by
the regulations (determined relative to
what would arise for a “reference
page 5
European Commission (EC), 2005.
“Green Paper on Energy Efficiency”.
[Internet] EC. Available at:
European Commission (EC), 2006. “
Promotion of European Passive Houses
(PEP)”. [Internet] PEP. Available at:
Government of Ireland, Department of
Communications, Energy and Natural
Resources (DCMNR), 2007. Government
“White Paper Delivering a Sustainable
Energy Future for Ireland”. [Internet]
DCERN. Available at:
dwelling” of the same dimensions) then
the dwelling is deemed to be compliant.
1.3.3 Building Energy Rating
A Building Energy Rating (BER) is an
objective scale of comparison for the
energy performance of a building
ranging from A1 to G (see graphic on
previous page). Essentially a BER is an
asset rating, based on a standardised
occupancy and usage pattern, and is
calculated for a dwelling using DEAP.
The rating is the annual primary energy
consumption of the dwelling expressed
in terms of kWh per m2 of floor area. The
CO2 emissions associated with this
energy consumption are also reported
on the BER certificate and expressed in
terms of kg of CO2 per m2 of floor area.
O’Leary, F., Howley, M., and
O’Gallachóir, B., 2006. “Energy in
Ireland 1990-2004, Trends, issues,
forecast and indicators”. Dublin.
Sustainable Energy Ireland.
O’Leary, F., Howley, M., and
O’Gallachóir, B., 2008, “Energy in the
Residential Sector: 2008 Report”.
Dublin. Sustainable Energy Ireland.
United Nations Framework Convention
on Climate Change (UNFCCC), 1997.
The Kyoto Protocol. [Internet]. UNFCCC.
Available at:
page 6
1.3.4 PHPP and DEAP
Whereas DEAP is the mandatory method
for both producing a Building Energy
Rating and for demonstrating compliance with certain aspects of the Irish
Building Regulations, the Passivhaus
Standard and the associated PHPP is a
voluntary design standard for achieving
low levels of total energy consumption
within a dwelling.
While it is to be expected that a dwelling
conforming to the Passivhaus Standard
will comply with Irish Building
Regulations Part L, a separate calculation
using DEAP will be required to demonstrate both this and to determine its BER.
The Passivhaus Standard can be met
using a variety of design strategies,
construction methods and technologies.
In general, the low energy consumption
required to meet the standard will result
in a dwelling achieving a favorable BER,
provided that attention is paid to the
advice outlined in later sections of these
Ireland’s 1st Passivhaus, Wicklow
Source: Tomás O’Leary, MosArt Architecture
A passive house is a building, for which thermal comfort (ISO 7730) can be achieved solely by
post-heating or post-cooling of the fresh air mass, which is required to fulfill sufficient indoor
air quality conditions (DIN 1946) - without a need for recirculated air. Source:
See news/ CEPHEUS_final_short.pdf
How to Design and Specify a
Passive House in Ireland
How to Design and Specify a Passive House in Ireland
This section introduces the passive
house building design process as well as
explaining the balance between energy
losses and gains. It also provides an
overview of the various building systems
and technologies typically employed in
a passive house and presents the PHPP
software used for energy balance calculations. The design and specification of
the example prototype passive house in
the Irish climate developed as part of
these guidelines will be covered in
greater detail in Section 3.
2.1 Building Design Process
for a Passive House
Client’s Brief
The design of a passive house will
typically commence with developing a
brief with the client, whether this is a
family wishing to build a single rural
dwelling, a Local Authority progressing a
housing scheme or a commercial developer proposing a mixed residential
project. The brief would typically outline
the client’s practical requirements in
terms of space functions and density
and also their preferred image or
concept for the building(s). Clients interested in building a passive house will
often have carried out some research on
the subject and so may already be
relatively well informed regarding the
benefits of living in a passive house.
Site Visit
A site visit is important to identify the
presence of structures, landform or
evergreen trees which might cast
shadows on the house during the short
winter days when the sun is low in the
sky (thus reducing the potential for
achieving a glazed south facing façade).
It may happen that the best views from
the site are to the north suggesting the
placement of large glazing areas on the
northern façade in order to exploit that
view. All orientation options must be
considered by the designer at this stage
– the house must not only function well
in terms of energy efficiency but also in
terms of optimising the potential of the
site and its surroundings.
Sketch Design
The next phase of the design process is
to develop a sketch design for the house.
The basic principles of passive house
design will greatly inform the development of the initial design. An ideal
approach would be to have the longest
façade of the house facing south, a bias
of glazing towards the southern elevation with reduced glazing area on the
northern elevation and a compact form
in order to minimise surface to volume
ratio. Shading devices may be required
in order to protect against the risk of
overheating in summer and the
aesthetic integration of this is essential.
In terms of internal layout, it is preferable
to organise, where possible, family
rooms and bedrooms on the southern
elevation with utility room and circulation spaces on the northern elevation
where availability of sunlight is not so
Initial Evaluation of Energy Performance
Once the sketch design has been
approved by the client, it is important to
test the energy balance of the house
design using the Passive House Planning
Package (PHPP). The essential elements
of the design are entered into the
spreadsheet, including U-values of walls,
floors, roof and glazing as well as orientation, volume, and size of the house.
This will provide an early indication of
whether the Passivhaus Standard is
being achieved.
If the space heat requirement is significantly above the threshold of 15
kWh/(m2a) then the building will have to
be modified whether in terms of
improved U-values, reorganisation of
glazing or adjustment of form. The
designer should intuitively know how
improvements can best be achieved
while broadly remaining true to the
agreed sketch design. If the space heat
requirement is significantly less than the
threshold level, then it might be possible
to increase the U-values and therefore
save on insulation costs.
Care should also be taken to note other
performance indicators calculated by
the software, such as frequency of
overheating, for example.
Detailed Design and Specification
The design of the house is next developed to the level of detail required to
apply for planning permission. Typically
this would not require all construction
details but it is wise to consider the
various technologies at this stage in
order to avoid difficulties later on.
The type of construction will need to be
considered, whether timber frame,
masonry, externally insulated masonry,
insulated concrete formwork, steel
frame or straw bale as well as the space
required for services such as solar
panels, large domestic hot water tank,
mechanical ventilation equipment with
supply and exhaust ducting. The specification of such services might be outside
the expertise of the house designer and
it may be required to commission the
services of a Mechanical and Electrical
page 9
Areas of Heat Loss in Homes
Flue Loss
Roof Loss 30%-35%
Loss through
Loss 25%
Window Loss 15%
Floor Loss 7%-10%
Comparison typical building fabric heat loss patterns
in a detached dwelling, excluding ventilation and infiltration (Source: UCD Energy Research Group)
It is also critically important to plan
ahead in terms of airtightness and cold
bridging detailing as these often represent the most challenging aspects of
passive house design.
It will usually be necessary to engage
specialist sub-contractors to supply and
install such elements as the ventilation
equipment, solar system, back up
heating systems and controls.
The detailed design should be re-tested
in the PHPP software to ensure that the
Passivhaus Standard is achieved. At this
stage all the required data fields have to
be completed as accurately as possible
(details of the PHPP tool datasheets are
outlined in section 2.2.1). The result of this
detailed test might suggest that minor
alterations are required to the initial
house design in order to meet the
passivhaus standard. The client should be
kept informed at all times of the decisions
being made by the design team and have
the opportunity to suggest alterations
should the need arise.
Post Construction Testing
This is the final stage to determine
whether the constructed dwelling
actually meets the airtightness requirements of the Passivhaus Standard. The
air-leakage must not exceed 0.6 air
changes per hour using 50 Pa (0.6ac/h @
50 Pa) overpressurisation and underpressurisation testing. An independent
inspection and testing body should
conduct the testing activities. It is important to undertake this test as soon as the
airtight layer is complete so that any
leaks can be rectified. Where the
dwelling does not meet the requirements further testing may be required.
Tender Documents and Drawings
Once planning permission has been
granted, a more detailed set of technical
drawings will be required in order to
enable the construction of the house. As
highlighted above, the emphasis will be
on detailing of junctions between different elements of the building, practical
requirements for minimising heat loss
through cold bridging, planning for
airtightness and the location and
routing of services. The sizing of the
ventilation equipment, backup space
heating, solar domestic hot water
system, as well as details of controls for
space and water heating and ventilation,
will have to be specified at this stage.
The detailed drawings and specification
can then be issued for tender to competent contractors.
Site Operations
The detailed design of the passive house
must now be realised on-site and quality
control is paramount to achieving the
standard envisaged in the PHPP
software. The most challenging aspect
will typically be achieving the required
level of airtightness, as this is greatly
affected by the quality of craftsmanship
on site. The challenge becomes all the
more difficult if the building contractor
has no prior experience of building to
the Passivhaus Standard. More challenging again is the common practice of the
house built by ‘direct labour’ and
without an experienced supervisor with
overall responsibility to achieve the high
standards set.
page 10
2.2 General Principles: Heat
Energy Losses and Heat
Energy Gains
Comparison of energy rating between different
German construction standards and the passive
house. (Source: Passivhaus Institut, Germany
2.2.1 Passive House Building
The building envelope consists of all
elements of the construction which
separate the indoor climate from the
outdoor climate. The aim of the passive
house is to construct a building
envelope that will minimise heat loss
and optimise solar and internal heat
gain to reduce the space heating
requirement to 15 kWh/(m2a).
Comparison between PHPP and DEAP
The dimensions used in PHPP are
always external dimensions (Figure DEAP calculates with internal
heat is lost through windows but heat
lost through external walls is very low. In
the conventional building, on the other
hand, there can be significant heat loss
from the entire building envelope,
especially through windows.
Calculation of building element areas using external
dimensions. Source PHPP 2007 Handbook, pg 37
The following building envelope parameters are fundamental in this process:
1. Well insulated building envelope
2. High energy performing windows
and doors
3. Minimised heat loss through thermal
4. Significantly reduced structural air
5. Optimal use of passive solar and
internal heat gains
Building Envelope Insulation
Many building methods can be used in
the construction of a passive house,
including masonry, lightweight frames
(timber and steel), prefabricated
elements, insulated concrete formwork,
straw bale and combinations of the
above. The prototype passive house
presented in this publication (details in
Section 3) illustrates both masonry and
timber frame construction as representative of the most typically used building
methods for dwellings in Ireland.
Continuous insulation of the entire
thermal envelope of a building is the
most effective measure to reduce heat
losses in order to meet the Passivhaus
A thermographic image can be used to
illustrate the difference between good
and poor levels of insulation in a house.
Heat loss through the building envelope
is highlighted by the green, yellow and
red colouring. The green areas represent
the best insulation whereas the red
represents the warmest outer surface
(hence the worst insulated). The amount
of thermal radiation emitted increases
with temperature, therefore warm
objects stand out well against cooler
backgrounds. In the passive house some
Insulation of the building envelope can
be divided into four distinct areas: external wall, floor, roof and windows.
Existing passive houses in Central and
Northern European countries have been
achieved with U-values for walls, floors
and roofs ranging from 0.09 to 0.15
W/(m2K) and average U-value for
windows (including glazing and
window frames) in the region of 0.60 to
0.80 W/(m2K). These U-values are far
below (i.e. better than) the limits
currently set under the Irish Building
Regulations, with the most marked
difference pertaining to windows, wall
and floor.
Irish Building Regulations, Elemental
Regulations Technical Guidance
Document L, Conservation of Fuel and
Energy TGD Part L 2007).
Maximum average elemental U-value
Pitched roof, insulation horizontal
at ceiling level 0.16
Pitched roof, insulation on slope
Flat roof 0.22
Walls 0.27
Ground Floors 0.25
Floors with underfloor heating
Other exposed floors 0.25
Windows and roof lights 2.00
A sensitivity analysis using the Passive
House Planning Package (PHPP), v.
2007, was undertaken using a range of
U-values for the timber frame and
masonry constructions of the prototype
house using climatic data for Dublin. In
all options tested, the same data input
was used for airtightness 0.6ac/[email protected],
ventilation and minimised thermal
bridging. Various parameters were
tested in order to determine, for
example, the required level of U-values
for the building envelope in the Irish
climate, and to ascertain whether it
would be possible to use double glazing
and still achieve the Passivhaus
Standard in Ireland. The results as
outlined below are: Option 1 being the
most energy efficient house and Option
8 being the least energy efficient. An
Thermal transmittance (U-value)
relates to a building component or
structure, and is a measure of the rate
at which heat passes through that
component or structure when unit
temperature difference is maintained
between the ambient air temperatures on each side. It is expressed in
units of Watts per square metre per
degree of air temperature difference
Conservation of Fuel and Energy (TGD
Part L) 2007.
Thermographic image illustrating difference in heat
loss through building envelope in a conventional and
passive house building.
page 11
U-values of roof
U-values of
U-value of
windows and
Space heating
0.10 W/(m 2K)
0.10 W/(m 2K)
0.10 W/(m 2K)
0.80 W/(m 2K)
7 kWh/(m2a)
0.15 W/(m 2K)
0.15 W/(m 2K)
0.15 W/(m 2K)
0.80 W/(m 2K)
12 kWh/(m2a)
0.175 W/(m 2K )
0.15 W/(m 2K)
0.15 W/(m 2K)
0.80 W/(m 2K)
13 kWh/(m2a)
0.10 W/(m 2K)
0.10 W/(m 2K)
0.10 W/(m 2K)
1.50 W/(m 2K)
20 kWh/(m2a)
0.27 W/(m 2K)
0.16 W/(m 2K)
0.25 W/(m 2K)
0.80 W/(m 2K)
20 kWh/(m2a)
0.10 W/(m 2K)
0.10 W/(m 2K)
0.10 W/(m 2K)
2.00 W/(m 2K)
31 kWh/(m2a)
0.15 W/(m 2K)
0.15 W/(m 2K)
0.15 W/(m 2K)
2.00 W/(m 2K)
37 kWh/(m2a)
0.27 W/(m 2K)
0.16 W/(m 2K)
0.25 W/(m 2K)
2.00 W/(m 2K)
48 kWh/(m2a)
U-values of
ext. wall
Sensitivity analysis of the prototype passive house in Ireland outline test results for eight options. Source: MosArt Architecture
outline description of each of the eight
options analysed is provided. Only the
first three achieve the Passivhaus
Standard set for annual space heating of
15 kWh/(m2a) treated floor area:
Option 1 – U-value 0.10 W/(m2K) for
all building elements combined with
triple glazed windows with average
U-value (including glazing and
window frames) of 0.80 W/(m2K)
results in space heating requirement
significantly below the standard
limit required of 15 kWh/(m2a).
Option 2 – U-value 0.15 W/(m2K) for
all building envelope elements
combined with triple glazing. The
results show space heating requirement below the Passivhaus Standard
Option 3 – this is the option that has
been used in the design of the
prototype passive house in Ireland
as part of these Guidelines, with Uvalue of 0.175 W/(m2K) for external
walls and U-value 0.15 W/(m2K) for
all other building envelope
elements, coupled with triple glazed
Option 4 - U-value for all building
envelope elements of 0.10 W/(m2K)
combined with an efficient double
glazed unit with low U-value of 1.5
W/(m2K ) which does not achieve the
Passivhaus Standard.
page 12
Note: Advantages and disadvantages of
using triple glazed windows are discussed
in detail in section ‘Windows & Doors’)
Option 5 – U-values for walls, roof
and floor employed at the limits of
the individual elemental heat loss
requirements in the Irish Building
Regulations, (Building Regulations
TGD Part L, Conservation of Fuel and
Energy 2005 and 2007) combined
with triple glazed windows, failing to
achieve the required standard.
Option 6 – also a failure is the combination of U-value 0.10 W/(m2K) for
building fabric in combination with
standard double glazed units.
Option 7 – U-values 0.15 W/(m2K) for
walls, roof and floor as the prototype
house but with standard double
glazing U-value 2.0 W/(m2K) which
comes way above the limits set for
the Passivhaus Standard.
Option 8 – U-values for walls, roof
and floor employed at the limits of
the individual elemental heat loss
requirements in the Irish Building
Regulations, (Building Regulations
TDG Part L, Conservation of Fuel and
Energy 2005 and 2007) and standard
double glazed units, failing to
achieve the Passivhaus Standard.
Note: Results presented here are indicative
only and should be used as starting point
for specification of a passive house
dwelling in Ireland. Meeting the
Passivhaus Standard must be tested and
verified with the PHPP software for the
specific dwelling design.
Thermal Conductivity
Thermal conductivity (λ-value) relates to
a material or substance, and is a measure
of the rate at which heat passes through
a uniform slab of unit thickness of that
material or substance, when unit
temperature difference is maintained
between its faces. It is expressed in units
of Watts per metre per degree (W/mK),
Conservation of Fuel and Energy 2007).
Insulation materials for walls, roofs and
floors vary in terms of thermal conductivity. Typical conductivities for different
insulation materials are included below
as well as the approximate thicknesses
required in order to achieve a wall (or
roof ) U-value of 0.15 W/(m2K) and 0.10
Typical insulation materials used in
Ireland include mineral/rockwool,
polystyrene, polyurethane, polyisocyanurate, sheep wool and hemp. Different
insulation materials may suit different
types of construction application and it is
important to consider the material best
suited for the situation and pay attention
to detail in its proper installation. For
example, quilted or loose fill insulation is
generally suitable for use on the floor of
an open attic space where it will fill
completely between ceiling joists, but
care needs to be taken in ensuring ventilation in the attic whilst avoiding risk of
wind displacement of insulation near
eaves. In contrast, rigid insulation may
be at lower risk of displacement by wind,
but would need to be cut perfectly to fit
snugly between the joists, to avoid a risk
of thermal looping or leakage. As a
further example, a high density rigid
insulation tends to be better suited
under a floor slab compared with insulation that easily compress or are affected
by moisture.
taking into account building orientation,
areas of glazing and specific types of
glazing so the optimum balance of
glazing for each passive house design
can be reached. Also, as highlighted
further below, there is a need for the
design to ensure that the risk of solar
overheating is minimised.
It has been illustrated above that the use
of windows and doors with average Uvalues of 0.8 W/(m2K) can be combined
with U-values for opaque elements of
0.15 W/(m2K) to comfortably achieve the
Passivhaus Standard in Ireland. There are
Light filled room in a passive house.
Source: MosArt Architecture.
The U-value of the construction is determined by the conductivity of materials
and components used from the internal
surface to the external surface of the
thermal envelope. Examples of typical
construction methods and materials
used for the prototype passive house in
Ireland are illustrated later in Section 3.
Windows & Doors
The recommended approach to the
design of a passive house is to have
avoid an excessive area of north facing
glazing and place relatively large
windows facing south or due south. This
is in order to minimise heat losses
through the north facing elevation,
which receives no direct sunlight during
most of the heating season, while
maximising ‘free’ solar heat gains on the
south. An advantage of large windows is
an increase in interior daylight levels
which in turn reduces the need for use of
electricity for artificial lighting and also
ensures a more pleasant natural lightfilled living environment.
There is, however, a balance to be
achieved between heat losses through
the glazing and solar heat gains through
the south/east/west facing windows.
When designing a passive house, the
PHPP software should be used to calculate the heat losses and heat gains
Comparison of the interior surface temperature depending of the type of glazing. Source: Internorm, fenster – Licht
und Leben catalogue 2007/2008, pp.91.
a number of advantages in using
windows with average U-values of 0.8
W/(m2K) as well as highly insulated
doors, principally the assurance of a
comfortable indoor climate due to the
lower cold radiation heat transfer at the
surface of the glass. One will not sense a
drop in temperature standing immediately adjacent to this standard of
window, unlike the experience of standing next to a conventional double
glazed unit with U-value, for example of
2.0 W/(m2K). An added benefit of using
highly energy efficient windows and
doors includes significant draught
reduction due to the fact that they have
typically two seals or gaskets (compared
with conventional double glazed units
which often have only one) as well as
excellent sound insulation. Finally,
conductivity W/mK
Thickness for
U-value of 0.15
Thickness for
U-value of 0.10
W/(m 2K)
Polyisocyuranate or
Polystyrene, sheep wool
Cellulose, Hemp and
Insulation Material
Conductivity of insulation materials and approximate thickness to achieve specific U-value for external walls (k
values will vary according to density). Source: MosArt Architecture
natural convection which is driven by
temperature difference between the
inside face of the glass and the room
interior is much reduced, thereby avoiding this source of cold air flows and
thermal discomfort.
The sensitivity analysis for a passive
house dwelling in Ireland showed that in
the case of Option 4 above the
Passivhaus Standard yearly space
heating requirement could not be
achieved with efficient double glazed
windows with a U-value of 1.5 W/(m2K).
Typically triple glazed window units are
used in passive houses in Central and
Northern Europe. The Passivhaus Institut
has certified a range of glazing and door
units suitable for use in passive house
buildings. Although it is not a prerequisite to use certified passive house
products ( in a
passive house, choosing approved
products means the validity of technical
data has been tested and verified by an
independent certifier. The principal
characteristics and advantages of using
triple glazed windows in a passive house
are listed below, for both glazing and the
page 13
With triple glazing the solar energy
transmittance (gs), i.e. the amount of
solar energy entering through that
glazing is somewhat reduced
compared to double glazing due to
the effect of the additional layer of
glass. A requirement of the
Passivhaus Standard is to use glazing
with minimum solar transmittance
of 50% or higher.
Cross section though a triple glazed insulated window
and frame. Source: MosArt Architecture.
Three panes of glass separated by
special low-conductivity spacers
eliminates the risk of condensation
at the bottom of the glass in cold
weather (which could lead to rotting
of timber frames over time);
High solar energy transmittance (g ≥
50), referring to the amount of solar
radiation which can penetrate the
glass and thereby contribute
towards heating of the dwelling;
A low emissivity (low-e) coating on
the inside of the outer two panes
which reduces thermal re-radiation
back out through the glass. It should
be noted that a ‘soft coat’ has slightly
better U-value but a ‘hard coat’
glazing has higher solar transmittances.
Insulating gases between the glass
panes, typically argon or krypton,
which help to reduce heat escaping
through the glass.
The quantity which describes the heat
loss associated with a thermal bridge is
its linear thermal transmittance (ψ).
This is a property of a thermal bridge
and is the rate of heat flow per degree
per unit length of bridge that is not
accounted for in the U-values of the
plane building elements containing
the thermal bridge.
Source: SEI, Dwelling Energy Assessment Procedure (DEAP) 2005 edition,
version 2, pp.55
page 14
The frame must be well insulated
and also have a thermal barrier (be
“thermally broken”). Even wood
conducts heat and a thermally
broken timber window frame will
result in much lower heat losses than
a solid one.
There will typically be two weather
gaskets on triple glazed windows
used in a passive house dwelling, the
primary function of the outer one
being for weathering with the inner
one serving to improve airtightness.
The majority of these types of
window open outwards which is
Europe; however, there are models
of inward opening windows being
developed which will be available
soon in the Irish market. One advantage of outward opening windows is
that they don’t intrude in the room
space which might be important in
more compact dwellings.
Triple glazed window frames are
typically much wider and stronger
construction than their conventional
double glazing counterparts.
The use of larger areas of glazing on the
south elevation is helpful in maximising
the amount of sunlight available in the
short days of winter. It must be remembered, however, that highly energy
efficient windows allow less daylight
(visible light transmittance) into a building than normal double glazed windows
without e-coating. Light transmittance is
an optical property that indicates the
amount of visible light being transmitted through the glazing. It varies
between 0 and 1 (0 to 100% light transmitted), representing the proportion of
light transmitted. A double glazed
window with low-e coating will typically
transmit 72% of visible light. A triple
glazed energy efficient window will
typically transmit 65% of visible light
(these are indicative values only - actual
values depend on the manufacturer’s
In a conventionally constructed older
house in Ireland radiators are typically
positioned under windows in order to
heat the cold air entering through the
single or double glazing. In a passive
house, locating a heat source beneath
windows is simply not required as the
heat load is transferred throughout the
house via the mechanical ventilation
system. This has the added benefit of
enabling unobstructed use for placing
furniture against all external walls.
Thermal Bridging
Thermal bridging (i.e. un-insulated joints
between walls, floors/ walls, ceilings/
adjacent walls, windows/walls etc) are
weak points of thermal resistance in the
building envelope and cause unwanted
losses of energy which should be eliminated or significantly reduced to a
degree that the associated heat losses
become negligible.
A thermal bridge increases heat loss
through the structure, and in some
extreme cases this may cause surface
condensation or interstitial condensation in the structure. Surface mould
growth or wood rot may be the consequences of a thermal bridge. Typical
effects of thermal bridges are:
Significantly increased heat losses;
Decreased interior surface temperature (cold spots) which may also
result in high humidity in parts of the
construction; and
Mould growth cause by warm internal air condensing on cold surfaces.
All of the above situations can be
avoided in houses built to the
Passivhaus Standard. The Passivhaus
Standard for linear thermal transmittance (Ψ) should not exceed 0.01 W/(mK).
This requires the building designer to
identify and locate all potential thermal
Comparison between PHPP and DEAP
Thermal bridges are calculated in PHPP
on the external face of the thermal
envelope whereas in DEAP the thermal
bridges are calculated on the internal
surface of the envelope.
bridging in the construction, applying
careful specification and detailing of
those elements providing where possible a continuous layer of insulation, as
well as taking care to execute those
elements on site as per design details.
Designing and building a passive house
in Ireland requires the development of
construction details that go far beyond
guidance provided (to avoid excessive
heat losses and local condensation) in
Building Regulations Technical Guidance
Document Part L, Conservation of Fuel
and Energy. Building practitioners could
refer to the accredited construction
details specifically developed for passive
house building published in Germany
“Thermal Bridge-Free Construction”
(PHPP 2007, pp.96). Thermal bridging
can be tested and verified in the PHPP
software as the design of the passive
house building is being developed.
Structural Airtightness and DraughtProofing
Building an airtight or leak-free structure
is imperative to achieving the Passivhaus
Standard. If there are gaps in the building structure then uncontrolled
amounts of cold external air can infiltrate the building. Achieving a high level
of airtightness eliminates cold draughts
and associated comfort losses. It also
prevents condensation of indoor moist,
warm air penetrating the structure, and
possible structural damages due to
decay, corrosion and frost.
Air tightness is achieved in masonry
construction by careful application of
appropriate membranes and tapes or
wet plastering within the building
envelope. A great deal of attention must
be paid to detailing and workmanship in
order to ensure that the airtight layer is
continuous all round the building,
especially around junctions between
walls and floors, roof, windows, doors,
etc. Penetrations of the airtight layer by
mechanical and electrical services must
be properly sealed.
The air tightness of a building can be
accurately measured by carrying out a
blower-door test. The test involves
placing a powerful fan suspended in a
sealed canvas sheet within a door
opening and operating the fan at very
high speeds thereby creating either
negative or positive pressure within the
house. By sucking air out of the house,
for example, a negative pressure is
created with the result that external air
will be sucked in through any gaps or
cracks in the building envelope. The
pressure used for such tests is 50 Pascal
which can be accurately set by the
blower door equipment.
When undertaking the test it is usually
quite easy to identify any major leaks
due to the presence of a strong draught
which can be felt by the hand or, for
smaller leaks, can be detected by a
thermographic camera. The cause of
these draughts can then be sealed with
appropriate materials as the test is on
going. It may also happen that the leaks
in the envelope are very minor and
therefore difficult to locate. In these
situations it is typical to reverse the
direction of the fan and blow air into the
house putting it under positive pressure.
Odorless smoke can then be released
into the building and leaks can be
observed from the outside where the
smoke appears through the envelope. It
is important to notify the fire service if
you are carrying out such a test in case it
is mistakenly reported as a house fire by
passers by.
Infrared image of the interior of a passive house
window. All surfaces (wall structure, window frame,
and the glazing) are pleasantly warm (over 17 °C). Even
at the glass edge, the temperature does not fall below
15 °C (light-green area)
(Source: Passivhaus Institut,
from the passive house Kranichstein)
For comparison, a typical older double glazed window
is shown. The centre of glass surface temperature is
below 14 °C. In addition, there are large thermal
bridges, particularly where the window meets the
external wall. The consequences are significant radiant
temperature asymmetry, drafts, and pooling of cold air
in the room.
(IR-photography: Passivhaus Institut offices, )
The Passivhaus Standard is reached
when there are less than or equal to 0.6
air changes per hour @50 Pa pressure.
The most critical issue regarding testing
for airtightness is timing during the
building process. It is important that
remedial measures can be carried out in
order to remedy any leaks or cracks. The
test should be carried out before second
fix carpentry, for example, where there
are no skirting boards or window boards
fitted and where the junctions covered
by such materials are still accessible and
can be sealed. The test should also be
carried out after all mechanical and
Comparison between PHPP and DEAP
In the ventilation sheet of PHPP the air
changes @ 50 Pa have to be entered.
The DEAP calculation uses air changes
@ normal pressure for its inputs.
Timber Frame I-Beam construction reducing thermal
bridging. Source: Passivhaus Institut, Germany.
The results of the blower door test @ 50
Pa have to be divided by 20 to enter
the correct value in DEAP
Example: 0.6 ac/hr / 20 = 0.03 ac/hr
Input PHPP: 0.6, Input DEAP: 0.03
page 15
electrical services that need to penetrate
the building envelope have been
installed. Otherwise, installing such
services after the test could severely
compromise the airtightness of the
Correctly insulated house avoiding thermal bridge.
Source: Passivhaus Institut, Germany
Continuous Airtight Membrane.
Source: Passivhaus Institut, Germany
Timber frame house pre-cladding fitted airtight
membrane. Source: Passivhaus Institut, Germany.
In a typical Irish house built in accordance with TGD Part F 2002 the method
in which habitable rooms are ventilated
has usually been via a hole in the wall or
ventilator in the windows of 6,500mm2
fitted with a controllable grille. Such
means of ventilation can result in large
amounts of cool external air infiltrating
the building depending on wind speed
and pressure. The same is true for open
chimneys or flues in conventional
In a passive house, on the other hand,
the supply of fresh air is provided by a
whole house mechanical ventilation
system with heat recovery which
negates the necessity for openings in
the wall or windows. Thereby draughts
are eliminated and structural air tightness is not compromised.
In developing the building design it is
very important to anticipate differential
movement and decay of adhesives and
chemical bonds by detailing junctions
which will assist in maintaining an
airtight layer for the life of the building.
Many excellent details, for example, can
be found at the website of the Scottish
( It can
also be important to use membranes
and plasters that are both airtight but
also vapour diffuse which allow the
structure to “breathe” to its cold side.
This means allowing moisture within the
structure to escape to the outside
thereby reducing the risk of interstitial
moisture and the threat of rot and decay
over time.
There are two measurements used to define airtightness, namely cubic metres of air
per square metre of exposed fabric per hour (m3/m2/hr) or air changes per hour (ACH).
While the measured result for the former is generally 20% greater than that of the
latter, the difference is practice greatly depends on the building form.
Example to convert:
The prototype house in section 3 has a volume of 503.40 m3 and a total envelope area
of 324.21 m2.
The blower door test result is assumed, with 0.6 ac/h @ 50 Pa
503.40 m3 x 0.6 ac/hr / 324.21 m2 = 0.47 m3/m2/hr
page 16
Passive Heat Gains
Passive heat gains in a passive house are
a result of the combination of solar gains
and internal gains.
Solar Heat Gains
Passive solar gain is optimised by providing an east-west alignment to the building, if possible with the site, resulting in
the longest façade facing south, and by
placing the majority of the glazing
towards the south. Very high quality
windows (average U-value ≤ 0.8
W/(m2K)) facing south will have a
positive thermal balance – they will have
more heat gain than heat loss throughout the year. Results of a recent parametric study by J. Schnieders of the
Passivhaus Institut “Climate Data for
Determination of Passive House Heat
Loads in Northwest Europe” illustrates
the relationship between the area of
south facing glazing and the space heat
demand for a passive house dwelling
located in Ireland (measured climate
data for Birr used). The parametric study
uses the first passive house built by Dr.
Wolfgang Feist of the Passivhaus Institut
as a case study building, shown below. It
can be seen that the space heating
demand initially decreases quite steeply
with increasing south facing glazing.
There are diminishing returns from
increasing the area of south facing glass,
however, and there eventually comes a
point where there is little or no benefit in
providing more south facing glass as the
net heat loss is greater than the heat
gains over the year.
There is no optimal ratio of glazing to
floor area that can be used as a rule of
thumb in deciding what proportion of a
given façade should be glazed. The area
of glass has to be determined as part of
the design verification procedure using
the PHPP software.
Internal Heat Gains
A passive house is very efficient at utilising ‘free’ internal heat gains from domestic household appliances, kitchen and
utility equipment, electronic equipment,
artificial lighting, and occupants. Heat
losses from stoves or boilers also
contribute towards the overall space
heating requirement as long as they are
positioned within the building envelope.
Occupants of the building also
contribute to meeting the heat load; a
Space Heat Demand / Heat Load
Ireland - Birr
U-Value Wall = 0.175 W/(m2K)
U-Value Window = 0.85 W/(m2K)
Space Heat Demand [kWh/(m2a)]
Heat Load [W/m2]
Area South Facing Windows [m2]
Source: Climate Data for the Determination of Passive House Heat Loads in Northwest Europe, J. Schnieders,
Passivhaus Institut, pp.17.
typical adult human continuously emits
100W of heat when stationary. A family
of five persons, therefore, can emit up to
0.5 kW of heat. This may seem like a
small amount but it equates to approximately one third of the total space heat
load for the prototype passive house
presented in Section 3.
Risk of Overheating
Placing extensive areas of glass on the
south facing façade in a well insulated
and airtight dwelling might lead to
overheating in warm sunny days. The
PHPP software will alert the designer to
any risk of overheating by calculating
the frequency of overheating and
expressing this as a percentage of the
year in which the internal temperature in
the house rises above 25˚C. If the
frequency of temperatures over this
comfort limit of 25˚C exceeds 10% of the
year (measurement referring to hours
rather than days), additional measures
for reducing overheating should be
included in the dwelling. To prevent
uncomfortable indoor temperatures in a
passive house dwelling it is recommended to specify shading devices
(blinds, overhangs or awnings, etc.)
which will let the low sun enter the
home in winter but prevent the high sun
entering in summer.
In the first Irish passive house in Wicklow
shading was not in place on south facing
glazing during the first summer and the
house did overheat. A balcony was
installed ahead of the second summer,
which significantly reduced the
frequency of overheating. In midsummer when the daylight hours are
long the sun only enters the building in
the middle period of the day while
during winter when the daylight hours
are short the low sun completely illuminates the entire interior of the building.
In the temperate climate in Ireland
where external temperature rarely
exceeds 25˚C, the risk of overheating can
be easily avoided by careful consideration of shading devices and provision of
openings for natural ventilation in
combination with thermal mass inside
the dwelling (exposed concrete floor;
masonry wall, etc.). In some cases the
mechanical ventilation system could be
used to distribute fresh air throughout
the building by switching to a ‘summer
bypass’ setting. This however should be
avoided where possible as the ventilation system will consume electricity
resulting in increased primary energy. It
is preferable that the dwelling designer
should employ ‘passive’ cooling strategies to minimise overheating.
2.2.2 Passive House Building Systems
No more than 0.6 air changes/hour at 50 Pascal
pressure should be observed in accordance with the
Passivhaus Standard. This should be checked for
compliance with a blower-door test which will
immediately highlight leaky areas. Airtightness can be
achieved through the use of membranes, roofing felts
and plasters combined with sealants and vapour diffusion resistant materials.
Source: UCD Energy Research Group
Deep roof overhang shades
upstairs windows
Balcony shades
downstairs windows
Location of overhang and balcony.
Source: MosArt Architecture.
As indicated earlier a passive house
does not need a conventional space
heating system of radiators or underfloor heating to maintain a comfortable
indoor climate. Instead, typically, the
following building services are required
in a passive house:
Mechanical ventilation system with
heat recovery which provides most
of the space heat requirement
Backup system capable of heating
the air passing through the dwelling
via mechanical ventilation to meet
Lighting contributes towards internal heat gains.
Source: MosArt Architecture.
page 17
Photo depicting how the low winter sun enters the
room below the overhang/awning/balcony.
Source: MosArt Architecture.
any auxiliary space heating needs,
expected to be small. Typical fuel
sources for the back up system
include biomass, gas, and in some
instances electricity (for example
‘green electricity’ from renewable
sources). The back up system is also
used to provide hot water, either
throughout the year or during
winter if a solar water heating
system is used during summer.
Each of these items is dealt with
separately in greater detail below.
Photo depicting how the house is shaded from the high
summer sun by the overhang/awning/balcony.
Source: MosArt Architecture.
Schematic of the supply air ducts, the extract air ducts
and the heat exchanger within mechanically ventilated house. Source: Passivhaus Institut.
The sommer-bypass can be used for cooling in the
summer if needed. Source: MosArt Architecture.
page 18
Given the lengths to which the designer
and builder must go to in terms of ensuring a highly insulated building envelope,
excellent airtightness and minimal
thermal bridging, it is important that the
building services in a passive house are
as energy efficient as possible. This is
especially critical in the case of the
mechanical ventilation heat recovery
system. Therefore, the required
efficiency of the mechanical ventilation
system with heat recovery for a passive
house dwelling is at least 75%. It is also
very important to consider comfort,
health and safety issues in the design of
the building services for a passive house,
ensuring for example that the backup
heating system is adequately sized to
deal with extreme weather conditions,
that filters in the ventilation equipment
are replaced regularly and that there is
an independent fresh air supply for any
combustion devices such as a boiler.
These and other issues are dealt with in
greater detail below.
Mechanical Heat Recovery Ventilation
An airtight house requires a welldesigned mechanical ventilation system
to provide good indoor air quality. A
passive house is ventilated using a
mechanical system which incorporates
air to air heat recovery (mechanical heat
recovery ventilation, or MHRV). Exhaust
air is extracted from rooms that typically
produce heat, moisture and unwanted
odours such as kitchens and bathrooms.
Before this air is expelled to the outside
it passes through a heat exchanger
where the heat is transferred to the
separate stream of incoming fresh air,
thereby eliminating the need to
completely heat the fresh air as it enters
the building. It is important to appreciate that the stale exhaust air and clean
fresh air do not mix in the heat
exchanger and therefore there is no risk
whatsoever of what might be referred to
as ‘sick building syndrome’. Rather, the
stale air and clean air is channelled
through closely spaced but separate
narrow sleeves in the core of the heat
Ventilation systems use electric power
and therefore have a slightly negative
impact on the primary energy consumption. This will have affect the Building
Energy Rating. In our example in Section
3, the energy used by the MHRV is about
10% of the annual primary energy
The benefits of having a whole-house
mechanical heat recovery ventilation
system (MHRV) are many, including:
Constant supply of the correct
amount of fresh air to all habitable
rooms thereby reducing indoor CO2
levels and removing the cause of
stuffiness and tiredness;
moisture-laden air from bathrooms,
utility rooms and kitchens as well as
ventilating noxious gases and
unwanted smells if present; and
A lowering in humidity levels reducing mould and fungus that may
appear over time and decreasing
dust mite levels.
There are databases (SAP Appendix Q or in which various MHRV
products are listed in terms of efficiency
and performance.
MHRV System Efficiency
The efficiency of the heat exchanger in
the MHRV determines the amount of
heat that can be recovered from the
exhaust air and, therefore, has a very
significant influence on the additional
space heating that may be required in a
passive house. The aim is to use the
warm exhaust air to raise the temperature of the cool fresh air to provide for
thermal comfort all around the house.
On a night where outside temperatures
are below freezing, the fresh air might be
raised to, for example, 18˚C having
passed through the MHRV. The
efficiency of sensible heat recovery
should exceed 75% for the nominal
range of flow rates specified for the unit
when measured in terms of the supply-
air side temperature ratio as described in
EN 13141-7:20041. Specifiers and designers should be wary of products claiming
extraordinary efficiency rates of 95% or
higher. The safest route is to install
equipment that has been independently
tested and verified by such bodies as the
Passivhaus Institut.
The graph below is based on actual
testing of the first Irish passive house in
Wicklow. It illustrates, for example, how
mechanical ventilation ensures good
indoor air quality by removing the high
concentrations of a tracer gas that was
deliberately released into the house as
part of the test procedure. In less than
1.5 hours the air quality in the house had
returned to normal.
Recommended Ventilation Rate
According to the Passivhaus Institut, the
appropriate air change rate for dwellings
is between 0.3 and 0.4 times the volume
of the building per hour, with a general
recommendation of leaning toward the
lower rate. This maintains high indoor air
quality while ensuring a comfortable
level of humidity and maximizing
energy savings.
Compliance with the Irish Building
Regulations Part F might require more air
changes per hour than the Passivhaus
Institut recommends. It is possible to
enter a higher air changing rate into the
PHPP which consequently leads to a slight
increase of the energy consumption.
Adjustment of Fan Speed and Exchange
Most MHRV machines have different
settings for different circumstances.
These are often referred to as a ‘party’
setting, where there are a lot of people
in the house and where additional fresh
air is required, and ‘holiday’ setting,
where the house is being left vacant and
the flow of air is reduced. Under normal
occupancy, the former of these settings
will use more energy and also decrease
the level of humidity whereas the latter
will use less energy and perhaps lead to
an increase in humidity.
0.45Wh for every m3 transported air in
the calculation of electricity (due to
MHRV). When designing a passive house
in Ireland the specific fan power should
be carefully considered as the electricity
consumed for fans has direct impact in
terms of primary energy performance
and hence the Building Energy Rating
(BER). Therefore, specific fan power for
fans should be less than 1 W/l/s .
Winter and Summer Mode
There are generally two ventilation
modes in a passive house: Summer
Mode and Winter Mode. In winter, the
MHRV uses the heat in the exhaust air to
warm the incoming fresh air. In summer,
a bypass in the equipment can be set to
open automatically (controlled by
thermostats) such that the incoming
fresh air is not heated. Alternatively in
summer natural cross ventilation may be
used and the MHRV system can be
switched off.
Insulation and Positioning of Duct Work
and Vents
It is very important to adequately
insulate the supply air ducting so that
there is minimal loss of temperature in
delivering warm air around the house.
The thickness of insulation generally
used in passive houses is between 6 cm
and 10 cm for ductwork. It is also preferable to locate the ducting within the
thermal envelope and to keep pipe runs
It is not advisable to constantly run the
equipment on the lower setting just to
save energy when the house is occupied.
MHRV machines uses surprisingly little
energy given the important role that
they play in the passive house. The PHPP
software uses a standard value of
Using a digital anemometer.
Source: MosArt Architecture
IR Concentration
The PHPP software suggests that 30m3
per person per hour should be provided
to dwellings to ensure good air quality.
These two measurements can be used to
choose an appropriately sized machine
for different dwelling designs. Taking the
prototype house presented later in
Section 3 as an example, an occupancy
of five persons would require 150 m3 of
fresh air delivered to the house per hour.
In terms of extract, the PHPP software
uses the following rates for different
room types as default values, kitchen =
60m3/h, bathroom = 40m3/h , shower =
20m3/h and WC = 20m3/h. In the prototype house these total 140 m3/h which is
close to the supply volume which will
ensure that the whole house system will
be balanced. The supply and extract
volumes can be accurately set by using a
digital anemometer and adjusting the
valves on the vents in each room as
required. A photograph of this process is
shown below.
Graph depicting how mechanical ventilation ensures a good indoor air quality by removing the high concentrations
of tracer gas that were inserted into the house under test conditions. Source: UCD Energy Research Group.
Ceiling air supply vent.
Source: MosArt Architecture.
page 19
noticeable. MHRV machines are generally housed in a well insulated casing
and noise should not be a critical issue.
Dust laden used air filter.
Source: MosArt Architecture.
Water to air heat exchanger unit.
Source: MosArt Architecture.
as short as possible by ideally positioning the MHRV unit in the centre of the
house. This requires careful planning at a
very early stage of building design.
Vents are normally placed in the ceiling
but can also be placed in the wall if
necessary. The air inlets are typically
designed to spread the air horizontally
across the ceiling, minimising downward
draughts. There should be a gap either
under or over the door of each room to
enable the easy movement of air from
one room to the next. If doors are fitted
tight without such a gap, rooms with
exhaust vents would be under negative
pressure and rooms with supply air
would be under positive pressure.
Fan and valve noises can be almost
completely eliminated by sound control
measures (e.g., vibration isolation
mounts, low air speed and acoustic
lining in ducts). The grilles on vents
generally guide incoming air along the
ceiling from where it uniformly diffuses
throughout the room at velocities that
are barely perceptible. If the ventilation
equipment is operating on a high
setting (‘Party Setting’) the noise of the
equipment and the air flow may be more
page 20
Maintaining Good Air Quality
It is important that attention is paid to
regular replacement of air-filters for both
incoming and exhaust air. Filters are
used not only to provide clean air for the
occupants but also to ensure that the
heat exchanger is not clogged with dust
and other matter. If the filters are not
regularly replaced (for example every six
to twelve months) and they themselves
become clogged with dirt the MHRV will
have to work harder to provide the same
volume of air to the house, thereby
increasing the speeds of the fans and,
ultimately, using more energy. In
countries where this system is relatively
new, occupants may not be aware of this
maintenance need and indoor air quality
may suffer as a consequence. Equipment
differs with respect to the types of filters
used; some have to be replaced while
others can be washed and reused.
In single family houses, the extractor
hood in the kitchen is sometimes
connected to the MHRV equipment to
extract kitchen smells and to use the
waste heat from cooking to warm the
incoming fresh air. In such instances, it is
very important that the hood is fitted
with a high quality filter that can easily
be cleaned or replaced in order to
prevent the built up of grease in the
ducting system which could be a health
and fire hazard.
What happens in the event of a power
If there is a loss of electricity (and the
dwelling has no backup generator) the
ventilation system will stop working and
the supply of fresh air will be cut off. If
power is lost for a short while (for
example a few hours), then there is likely
to be no noticeable difference in indoor
air quality. If the loss of power is
prolonged, the simple solution is to open
the windows and to create natural cross
flow ventilation through the building.
Backup Heating System
As previously highlighted in these
guidelines, space heating requirement
in a passive house is so low that there is
no need for a traditional space heating
system. The optimal way to transfer the
small amount of required heat through-
out the house is through the mechanical
ventilation system. This section of the
guidelines will provide an overview of
the typical backup heating systems used
in passive houses to provide thermal
It is recommended to use high efficiency
heat generation systems for this auxiliary
purpose. The HARP database (viewable
on provides output and
efficiency data on a wide range of boilers
and other heating appliances, and is
updated on a monthly basis.
Insulated distribution pipes and hot
water cylinders are mandatory to reduce
the heat losses, achieve a quicker
response and increase the efficiency of
the heating and hot water system. The
details (length of pipes, size of hot water
storage, thickness and thermal conductivity of the insulation) can be entered
into PHPP.
Furthermore the fuel has to be taken
into account. Electric energy has a
primary energy factor of 2.7 whereby for
gas or oil the factor is 1.1. Where practicable therefore, the use of electrical
heating appliances should be avoided to
prevent incurring such a penalty in
primary energy use, which will have an
adverse effect on the Building Energy
Rating (BER) using the official DEAP
methodology. This penalty is greatly
reduced if using a correctly sized and
high efficiency heat pump for such an
auxiliary purpose.
PHPP specifies for wood pellets, chips
and logs a primary energy factor of 0.2.
Because DEAP calculates with a primary
energy factor of 1.1 for wood based fuel
the results for the primary energy
demand for space heating and DHW
differ significantly between PHPP and
Space heating demand in a passive
house is typically met through passive
solar gains (40 – 60 %), internal heat
gains (20 - 30%) and the remainder (10 40%) needs to be provided from auxiliary heating systems .
The PHPP software will accurately
predict the following two measurements for each passive house design:
Annual Space Heat Requirement –
this measures the amount of energy
that is needed to maintain a
comfortable indoor temperature,
specified in kilowatt hours per
square metre of treated floor area
per year, or kWh/(m2a).
Heat Load – this measures the capacity of the space heating system
required to maintain comfortable
indoor temperatures at any one
time, specified in Watts per square
metre of treated floor area, or W/m2.
For the prototype house the annual
space heat requirement (without losses
of the heating system) is 13 kWh/(m2a).
Including the losses the so called final
energy is 26 kWh/(m2a) equating to
approximately 2,860 kWh over an entire
year (the house measures 110m2 in
treated floor area).This would equate to
270 litres/year of oil, 280 m3/year of
mains gas or 570 kg/year of wood pellets
(in bags)
The heat load, on the other hand, is
approximately 1,800 W, or just 1.8 kW.
This amount of energy could be
provided by a very small stove / heater /
boiler compared to what might be
typically required in a family home.
The most common method of ‘heating’
in a passive house is by post-heating the
fresh air after it has already been
warmed by the exhaust air in the MHRV.
There are a number of ways in which the
temperature of the air can be boosted,
including those listed below:
Water to air heat exchanger;
Compact unit with electrical heat
Wood pellet/wood log boiler; and
Compact unit with natural gas
The first three of these are explored in
outline below. The compact unit with
natural gas, while used in Central
Europe, is virtually unheard of in Ireland
and would have to be approved for use
by the appropriate authorities.
Water to Air Heat Exchanger
This method involves using a heating
device placed immediately on the fresh
air supply outlet of the MHRV. There is a
small radiator inside this device and it is
heated by hot water connected to the
domestic hot water tank. If the house
needs additional heat (which is determined by a thermostat) then hot water is
circulated through the device, hence the
title of ‘water to air heat exchanger’.
Once the house has reached the
programmed temperature, the hot
water stops circulating and the air is no
longer heated. The water in the domestic hot water (DHW) tank is heated, in
turn, by using a number of energy
sources including a stove or boiler (for a
larger house) in combination with solar
hot water panels. The principal advantage of this system over the compact
unit system described below is that
when fueled by a combination of
firewood and sunshine it is carbon
Compact Unit with Electrical Heat Pump
This system is so-named as it incorporates all of the technology required for a
passive house in a relatively small unit,
namely the MHRV, the DHW and the
heating power for the home, in this case
powered by an electrically powered heat
pump. It is therefore very suited to
smaller homes where space might be
limited for large tanks, stoves and
storage for wood. It is important to use a
heat pump with the highest possible
efficiency (coefficient of performance or
CoP) based on test results for these
circumstances of use. Compact units are
becoming more widespread in use in
passive houses built in Central and
Northern Europe.
A 3D model of a typical compact unit is
illustrated right.
An independent combustion air
supply must be provided to any
stove or boiler in a passive house
bearing in mind the level of airtightness that has to be achieved. The
provisions of an air supply and flue
for stoves or boilers will generally
not significantly impact on airtightness or the balancing of ventilation
flows due to the ‘closed’ nature of
their construction. Air required for
combustion is drawn in through a
relatively small diameter duct and
expelled through the flue.
Most wood stoves are highly
efficient (up to 80 – 90%) and when
burning pellets there is very little ash
remaining following combustion. A
flue will be required to take exhaust
gas emissions safely away from the
house, as with any typical stove.
A stove or boiler that directs most of
the heat output to the DHW tank is
essential if the hot water is to be used
to heat the ventilation air. If there is a
need to back up the MHRV the stored
hot water will be used to re-heat the
fresh air. This system can be used in
combination with thermal solar
panels or other heat sources. A
model that simply radiates all the
heat into the space in which it is
located cannot generally be used for
whole house heating. Besides, it
should be appreciated that there is a
Wood pellet/wood log boiler
Wood pellets or wood logs can be used
as a heat source for a simple stove, back
boiler or for a boiler in the plant room to
serve as an auxiliary or backup source of
heat. The following issues should be
installing a wood stove or boiler:
Pellet boilers are available in types
loaded automatically or manually,
whereas wood log boilers for domestic
use are only manually charged.
The equipment must be sized appropriately to the heat load of the
house. This will be defined by the
‘Verification page’ in the PHPP
software. Taking the prototype
house presented in these guidelines,
a stove of 3kW output would be
sufficient for all space heating and
DHW needs.
Compact unit including ventilation heat recovery and
air to water heat pump. (Source: Passivhaus Institut,
page 21
high risk of overheating when using
a room heater or back boiler in the
living area because passive houses
have very low heat losses through
the building envelope.
As previously indicated, it will often
be logical for such units to be used
for not only auxiliary space heating
but also for auxiliary water heating.
Although the demand for such wood
fuel will be low, a dry space for
storage has to be provided. Wood
(whether logs, chipped or in pellets)
is bulky and a considerable volume is
required for storage especially if it is
purchased in bulk to keep costs to a
minimum.It is recommended that
the demand of at least 1.5 years is
stocked up. The consumption of
pellets in the example in Section 3 is
about 0.5 tonnes per year.
Integrated controls for heating in a
Passive House
Heating systems in Ireland have traditionally been simple, with among the
most common boiler based systems
being a timer and a cylinder thermostat,
and with sometimes even room thermostats being absent. However, the
Building Regulations Part L require
minimum levels of control, installing
equipment to achieve the following:
Automatic control of space heating
on the basis of room temperature;
Automatic control of heat input to
stored hot water on the basis of
stored water temperature;
Separate and independent automatic time control of space heating
and hot water;
Shut down of boiler or other heat
source when there is no demand for
either space or water heating from
that source.
Additional control features can be incorporated to a heating system so the
overall system performance improves.
One example is the ‘weather compensation’ feature, which is the ability to
adjust the output of the system based
on the measured external temperature.
The main advantage of using weather
compensation is that the heating system
closely monitors external temperature
trends and adjusts the output accordingly. If, for example, the external
temperature starts to drop rapidly, the
system can ‘anticipate’ that the dwelling
may come under pressure to maintain its
current internal temperature and can
verify whether there is sufficient power
to generate the backup heat that might
be required.
The preferred internal temperature can
be set using an internal thermostat. If
the internal temperature goes below the
thermostat setting, the system will
automatically start to heat the fresh air
passing through the ventilation equipment. The principal function of the
heating control system is to ensure that
there is always sufficient heat in the
buffer tank to deliver the heat load
required to maintain the comfort levels
set by the occupants. In the case of the
Out of the Blue demonstration house, if
there is insufficient heat in the buffer
tank, and the solar input can not cover
the heat demand at that particular time,
the pellet stove can be ignited automatically to provide the backup required.
The pellet stove will then cut out when
there is sufficient energy available. A
similar control system is found in the
compact units, except that a heat pump
is used instead of a pellet stove.
The amount of heat delivered to the
fresh air by the heat exchanger is
regulated by the internal and external
temperatures. The control system is
usually set up to deliver a relatively high
heat load if the temperature outside is
very cold, or alternatively a low heat load
if it is not too cold.
It would also be possible to use an
‘instantaneous’ system eliminating the
need for a large buffer tank. Such
systems do not typically suit the use of a
pellet boiler, however, as the boiler
would have to switch on and off for
short periods of time to maintain an
even temperature in the house.
The PHPP software assumes that the
heating system is controlled by
programmable timer and thermostats.
However, the use of DEAP needs more
detailed input data from the designer,
specifier or BER assessor on the auxiliary
heat generation, distribution and
control system here.
Schematic of mechanical system that can be used for back-up heating in a passive house.
Source: Passivhaus Institut, Germany (
page 22
Individual Room Temperature Control
Different rooms may have different
temperatures due to solar gains, occupation and internal heat loads. Room
based temperature controls for temperature differentiation between different
rooms may be necessary if individual
comfort requirements are set for different rooms. In a centralised ventilation
heating system, however, the supply air
temperature is relatively constant for the
whole house and this would be typical
for most houses built to the Passivhaus
litres of oil. Many people would be
surprised to learn that Dublin receives a
similar amount of annual irradiation as
Domestic Hot Water Production
As in any type of dwelling, the passive
house requires a system that provides
domestic hot water (DHW). As with
space heating, it is important that the
system is energy efficient, well
controlled and has an adequate capacity
to meet demand. Generally the DHW
system in a passive house is combined
with a heat source such as a wood stove,
solar thermal collector, compact unit or
heat pump for space heating. Most
passive house examples encountered
have utilised solar thermal collectors as
they reduce the use of primary energy
and CO2 emissions. It is important to
note, however, that the Passivhaus
Standard is indeed achievable without
solar based water heating. The introduction of Building Energy Rating system as
an indication of the energy performance
of dwellings in Ireland, together with the
mandatory requirement in the Building
Regulations Part L 2007 in relation to
renewable energy provision is likely to
increase the installation of solar technology.
The table over the page shows that the
solar input and gain are dependent on
the efficiency, orientation and angle of
the solar collectors.
The required volume of DHW is dependent on occupancy. PHPP assumes 35 m2
treated floor area per person. It is also
possible to enter in the verification sheet
the actual number of occupants. The
default settings for DHW in PHPP are 25 l
per person per day with a flow temperature of 60° C.
Assuming an area of 7.5 m2 south orientated flat plate solar collectors with a tilt
of 45° the solar contribution in our
example is 60% of DHW demand. The
remaining energy for DHW has to be
provided by the backup heating system.
In terms of specifying a solar collector
system, the following outline guidance
should be considered:
The optimal orientation is directly
due south and deviation from this
will reduce the contribution of the
collectors to DHW production. In
places where there is no south facing
roof, correspondingly larger panel
areas can be fitted to east or west
facing roofs.
The optimal tilt of the solar panels to
meet approximately 50% of the
annual heating demand for DHW is
approximately 45 degrees (in a pitch
that is greater than 45 degrees the
potential annual output is compromised somewhat).
There are two types of solar collectors typically used, namely flat plate
panels and evacuated tubes.
A comparison of the performance of
these types, based on 5m2 collector area,
along with consideration of orientation
and angle of incidence, is provided in
the table over the page. The calculation
was developed as part of these guidelines for the prototype passive house
using the calculation methodology for
solar water heating in the Dwelling
Energy Assessment Procedure (DEAP
2005, version 2).
Three different inclinations of solar
panels (30˚, 45˚, 60˚) and three different
orientations were calculated, with the
number of 3.6 occupants according to
DEAP assumption, water storage tank
300 litres, with 150 litres dedicated to
solar, and 50mm factory insulation, with
thermostat control.
As a general rule of thumb, the area
of solar panels is roughly 1 to 2 m2 of
collector area per person. The
system should be capable of providing up to 50 litres of DHW per person
per day in season.
In terms of sizing a solar tank, a
minimum of 80 and preferably 100
litres storage per m2 of collector
should be provided. In a typical Irish
home this could mean installing a
tank of between 300 and 500 litres
capacity. It is important to use a
proper solar water tank which is very
well insulated. Insulation of hot
water pipes is also important for
energy conservation, the thickness
Approximately 530 kWh/yr of useful
heat per person plus provision for
storage losses and distribution losses
must be supplied.
Domestic Water Heating – Solar Input
It is reasonable to expect that an
optimized solar based system (flat plate
or evacuated tubes of 5-7m2 area) will
produce up to 60% of total annual hot
water demand in the Irish climate. They
tend to have a relatively shorter pay
back period in comparison to other
renewable energy technologies such as
wind turbines or photovoltaic panels. In
Ireland the amount of solar irradiation
received each year is approximately 9001150 kWh/ma. After conversion into
heat, this is the equivalent of over 30
Yearly total of global horizontal irradiation (kWh/m2) UK and Ireland. Source: European Commission Directorate
General, Joint Research Centre
page 23
5 square meters of FLAT PLATE collectors (η
η0=0.75 and a1=6)
No obstructions:
Solar Input kWh/year
Tilt of collector
Solar input to demand ratio
Tilt of collector
5 square meters of EVACUATED TUBE collectors (η0=0.6 and a1=3)
No obstructions:
Solar Input kWh/year
Tilt of collector
Comparison between PHPP and DEAP
Primary energy factor (most important
Solar input to demand ratio
Tilt of collector
Wood Pellets/Log/Chip
Domestic solar water heating - solar input (flat plate collectors and evacuated tube) for the prototype passive house
(described in Section 3), calculated with the Dwelling Energy Assessment Procedure DEAP 2005 version 2.
Source: UCD Energy Research Group.
of insulation should be at least
equivalent to the pipe diameter and
preferably 1.3 times the pipe diameter.
The 40% or more of DHW needs that are
not provided by solar energy can be met
by several means including biomass
boilers or stoves, immersion heaters or
natural gas. An outline of the first of
these is provided below. It must be
remembered that space heating in a
passive house is often provided by using
hot water to heat the air passing
through the ventilation system. In such
cases, hot water production is essential
in the heating season when solar panels
on the roof will not be sufficient to meet
the demand for heating the hot water.
Accordingly, many passive houses will
have a biomass stove burning either
natural logs or wood chip or pellets. An
advantage of the last two of these is that
they are more easily automated so that
they fire up and switch off in the same
way as a conventional gas or oil burner.
page 24
the house including all household appliances and lighting. In order to achieve
the above mentioned Passivhaus
Standard it is necessary to specify refrigerators, freezers, cookers, artificial lighting, washing machines, dryers, etc. with
the highest energy efficiency available
on the market (i.e. category ‘A’ energy
rated household appliances). The
second step is calculating the auxiliary
electricity requirement, in which
electricity consumption is specified for
mechanical ventilation system fans and
controls, DHW circulation pumps, and
any other present in the dwelling.
Calculation results are presented in
primary energy kWh/(m2a) and included
in the PHPP ‘Verification page’.
Electricity Consumption in a Passive
The Passivhaus Standard primary
energy requirement has a limit of 120
kWh/(m2 year), regardless of energy
source for all space and water heating,
ventilation, electricity for fans and
pumps, household appliances, and
lighting energy requirements of the
house. This limit means that in a passive
house the efficiency of household
appliances and all electrical systems is
crucial to meet this challenging requirement. This is emphasised with the fact
that the primary energy factor for
electricity taken in the PHPP software
(as well as in the DEAP, Dwelling Energy
Assessment Procedure) is 2.7. Therefore
1kWh electricity used in a passive
house accounts for 2.7kWh of primary
When designing a passive house, the
PHPP software is used to calculate the
electricity balance. The first step is to
calculate the electricity requirement in
2.3 Energy Balance
Calculations and Passive
House Specification
2.3.1 PHPP Software and
An introduction to the PHPP was
provided at the beginning of this
Section within a discussion of the building design process for passive houses.
PHPP is a software package based on a
series of extensive and interlinked Excel
data sheets which collectively allow
building designs to be verified against
the Passivhaus Standard. The latest
version of the PHPP software can be
purchased for a nominal fee from SEI
Renewable Energy Information Office.
The verification requires the input of
very specific and detailed data about the
design, materials and components into
the PHPP spreadsheets and is then
related to the climate data for the region
in which the house would be built. The
validity of the result from this process is
of course highly dependent upon the
validity of the data entered.
Some of the principal datasheets
included in the software are listed
below, along with their main functions:
Climate data – it is possible to
choose the climate which the
passive house is being designed for.
This has a potentially significant
impact on the U-values required to
achieve the threshold annual heat
Verification – this sheet collates the
results of the overall evaluation of
the building including the space
heating requirement, specific
primary energy requirement, heat
load and frequency of overheating.
The user can see at a glance on this
sheet whether or not the building
can be certified as a Passive House.
U-value – this sheet enables the
assessor to specify the construction
of all the opaque (ie. does not
include windows) elements of the
building envelope for the purposes
of calculating the U-values of those
elements. The sheet requires the
input of the lambda value of the
building materials proposed as well
as their thicknesses and the proportion of insulation occupied by structural elements.
Windows – the orientation and size
of all windows is entered into this
sheet, along with the U-values of the
glass and frames as well as other
technical specifications which have
discussed earlier in this Section.
Annual Heat Requirement – this
value is calculated by determining
the heat losses through transmission
and ventilation and subtracting the
total solar and internal heat gains.
The annual heat requirement must
be less than 15 kWh/(m2a).
Heat Load – the building’s heat load
is based on energy balance calculations estimated by subtracting the
minimum solar gains and internal
heat sources from the maximum
transmission and ventilation heat
The PHPP software is comprehensive
and detailed and therefore requires
some training prior to embarking on
practical application to a real project.
However, the software is also quite user
friendly and the Verification page
enables the user to check whether or not
such thresholds such as Space Heating
Requirement are met. In the event that
the key Passivhaus Standard criteria are
not met, for example, the assessor will
firstly have to check to see if there are
any fundamental errors in terms of data
entry. If this is not the cause of the
problem, then the building will likely
have to be modified in order to achieve
the required standards. This will typically
involve improving the U values of the
building envelope, or altering the
proportion and orientation of glazing.
Extracts from the PHPP software are
included later in Section 3 pertaining to
the prototype passive houses.
2.3.2 Passive House Certification
At the time of writing these Guidelines, a
passive house in Ireland can be certified
by the Passivhaus Institut in Darmstad,
Germany ( ) or
certifying body approved by the
Passivhaus Institut. For further information on certification of passive houses in
Ireland contact the SEI Renewable
Energy Information Office or the
Passivhaus Institut directly. The evaluation criteria for the certification (Source:
PHPP 2007, pp.23) are:
Specific Space Heat Demand
max. 15 kWh/(m2a)
Pressurisation Test Result n50
max. 0.6ac/h
Entire Specific Primary Energy
Demand max. 120kWh/(m2a) including domestic electricity.
The above criteria have to be verified
with the PHPP 2007, and the required list
of documentation for the passive house
quality approval certificate, construction
drawings and technical specification
with product data sheets, must be
submitted to the certifying party
(including PHPP calculations). Also,
verification of the airtight building
envelope according to IS EN 13829, a
record of adjustment of the ventilation
system, declaration of the construction
supervisor and photographs of the
complete building must also be submitted. Upon examination of received
documentation the applicant receives
the results of the examination from the
Passivhaus Institut Certificate example, Quality
Approved Passive House.
Source: Passivhaus Institut, Germany.
certifying party. If the necessary verifications have been found to be correct and
the above criteria have been met the
‘Quality Approved Passive House Dr.
Wolfgang Feist’ certificate is issued
(PHPP 2007, pp.28).
A wider European passive house certification scheme was developed within the
project (2005-2007) “Promotion of
European Passive Houses, PEP”
This certification scheme is applicable to
‘an emerging market scenario’ (i.e.
countries with small number of passive
house building), aims to ensure that the
design of a particular passive house can
deliver the specific energy requirements
in accordance with the PHPP and confirm
the airtightness of the completed building. This certification scheme involves
the verification of the 'as built' design (i.e.
that reflects the actual construction,
incorporating any modifications made
during construction) in accordance with
the PHPP and confirmation of the air
tightness of the completed building by a
fan pressurization test performed in
accordance with IS EN 13829.
Since the above assessment criteria
apply to the 'as built' design details and
the completed building, there is a significant risk that any non compliances due
to fundamental errors will be difficult to
correct when the building is complete. It
page 25
Januray 2006 - November 2007 OUT OF THE BLUE TEMPERATURES
Degree Celsius
Bathroom Down
Main bedroom
Living room
External Temperature
Jan Feb Mar Apr May Jun Jul
Aug Sep Oct Nov Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Average daily temperatures, January 2006 – November 2007, monitoring results for the first passive house in Wicklow. Source: UCD Energy Research Group.
is therefore recommended that the
design is checked against the PHPP
before construction is started to confirm
that the criteria for the specific heating
and primary energy requirements are
met, that the construction on site is
checked to ensure that the dwelling
design has been realised and that air
permeability measurements are made
during the construction process so that
air leakage problems can be identified
and remedied while access to the
membranes etc is still available.
Since the actual performance of the
building will be very dependent on the
correct operation and maintenance by
the occupant, it is recommended that
adequate written information and
instructions are provided to the
occupants, at the time when the certificate is issued. Also, an approach to certification of products and technologies
used in passive house designs has been
developed. (Source: PEP Promotion of
European Passive Houses, passive
certification, ).
For further information on passive house
certification in Ireland contact
Sustainable Energy Ireland Renewable
Energy Information Office, SEI REIO
email: [email protected]
Lifestyle Issues
It is a common misconception that
windows cannot be opened in a passive
page 26
house. They can indeed be opened but
they don’t have to be opened. In a
passive house the ventilation system
ensures that a constant controlled
amount of fresh air is circulated around
the house so a stuffy or uncomfortable
atmosphere is avoided. If the occupants
would prefer to have the windows open
at night or provide natural cross ventilation during a hot summer’s day then it is
entirely possible to open whatever
windows or doors one chooses. The
MHRV should be switched off if there are
a lot of windows or doors being left
open as it would be an unnecessary
waste of electrical energy.
Living in a passive house encourages a
greater interest in and awareness of
weather patterns and the impact they
have (or don’t have) on indoor climate.
The passing of cloud cover brings with it
instant brightness and rising temperatures on the display panel for the solar
collectors. A very hard frost will
sometimes leave a veil of ice crystals on
the outside pane of the glazing which
rapidly melts in the morning sunshine.
Extremely cold clear weather usually
means that the backup heating is not
required during the day due to the high
levels of solar irradiation available. Dull
muggy days, on the other hand, while
not especially cold, may well require the
use of the pellet stove due to the lack of
sunlight. Windows may have to be flung
open to cool the house on New Years Eve
night depending on how many friends
and neighbours you manage to attract
to join the celebrations!
As an illustration of the indoor temperature comfort, monitoring results of the
room temperatures in the passive house
in Wicklow and site measured temperature is shown below. The graph represents measured average indoor and
outdoor temperatures from January
2006 to November 2007.
The above diagram illustrates temperature variation in different parts of the
house and cooler average temperatures
in the first heating season (early 2006)
compared to the second and third
heating seasons (late 2006 / early 2007
and late 2007 respectively). The reasons
for these variations are interesting and
warrant some elaboration, below:
The three coolest rooms (‘office’,
‘garage’ and ‘bathroom down’) are
each on the north side of the building, receive no direct sunlight during
the winter months and are very
infrequently used compared to the
remainder of the house. The first two
of these spaces have three external
walls and so are more prone to heat
losses compared with the rest of the
The three warmest rooms (‘kitchen’,
‘main bedroom’ and ‘stairs’) all open
out to the south of the house and so
receive the maximum amount of
solar gain in winter. Furthermore,
they are occupied for significant
parts of the day and / or night.
In the first few months of 2006, the
only backup heat source in the
house was a pellet boiler in the
sitting room. This alone was insufficient to heat the entire house as its
direct output into the room is just
2kW. As a result, those rooms on the
northern side of the house were
below thermal comfort levels for the
first few months of 2006. This went
largely unnoticed by the family due
to the fact that the rooms in
question are not used. Since then
the temperatures have continued to
In the autumn of 2006, a water-to-air
heat exchanger was fitted to the
MHRV equipment which enabled
heating the fresh air as it passes
throughout the house. This was
actively used for the first time in
December 2006 which resulted in
raising the temperatures in all rooms
(even those three on the north side)
to well within the normal comfort
level. In late 2007 the temperatures
have improved yet again.
There is still in evidence a temperature gradient (increasing in temperature) from north to south and from
first floor to ground floor.
The specification of materials and very
high quality build creates a strong sense
of living in a well-built house that will
last the test of time. The heavy doors and
windows close with a reassuringly solid
‘clunk’ and keep out draughts and
reduce external noise. The walls are thick
and substantial and are packed full of
insulation to keep out the cold and the
heat in. There is no condensation on the
internal glazing early on a cold morning.
The health aspects of living in a mechanically ventilated house are also readily
apparent, with no lingering odours, little
or no condensation in washrooms after
showering and an overall sense of high
indoor air quality throughout. Changing
the filters on the ventilation system is
always an eye opener – seeing what dust
and dirt is taken out of the incoming air
and what is extracted from the indoor
Living in a house that has a low carbon
footprint can bring about other changes
in lifestyle that are positive for the
environment, including growing your
own food and reducing the impact of
travel whether by car or by plane.
Raising children in a passive house will
also bring about positive change for the
next generation who will expect to
improve even further on what their
parents achieved.
Perhaps the overall lifestyle benefit of
living in a passive house is that it
provides very high levels of overall
comfort without compromising the
environment and at a fraction of the cost
of living in a traditional so-called
‘normal’ house .
Passive House Planning Package 2007,
16:Waermedrueckenfreis Konstruiren
(Thermal Bridge-Free Construction)”,
pp.96. PHPP 2007 Technical
Information PHI-2007/1(E), Passive
House Institut, Dr. Wolfgang Feist.
Passive House Planning Package 2007,
“Certification of Passive Houses”, pp.28.
PHPP 2007 Technical Information PHI2007/1(E), Passive House Institut, Dr.
Wolfgang Feist.
European Commission (EC), 2006. “
Promotion of European Passive Houses
(PEP)”. [Internet] PEP. Available at:
Schnieders J. 2006, “Climate Data for
Determination of Passive House Heat
Loads in Northwest Europe”.
Darmstadt, Germany, Passivhaus
IS EN 13141-7:2004, Ventilation for
buildings/ performance testing of
components/products for residential
ventilation. Performance testing of a
mechanical supply and exhaust ventilation units (including heat recovery) for
intended for single family dwellings.
Thermal comfort is defined in British
Standard IS EN ISO 7730 as: ‘that condition of mind which expresses satisfaction with the thermal environment.’ It is
affected by the key environmental
factors as air temperature, radiant
temperature, air velocity and humidity.
page 27
Passive House Prototype for Application in Ireland
Passive House Prototype for Application in Ireland
This Section of the guidelines demonstrates the practical application of
Passivhaus Standard to a prototype
passive house designed with a view to
its suitability for the mass housing
market in Ireland. The house type
demonstrated is a semi-detached two
storey house1 measuring approximately
110m2. The house is depicted in plan
and elevation below. The house is
typical in most aspects of its design,
comprising three bedrooms upstairs
(including one ensuite and family
bathroom) and a living room, dining
room, kitchen / utility and wheelchair
accessible WC downstairs. There are also
some non-conventional elements
including a double-height sun room,
solar panels, pellet boiler and shading
pergola. These are all described in
greater detail below.
The final part of this section examines
the capital construction costs associated with the passive house.
3.1 Design and Specification
The two most common construction
methods in Ireland were used in the
design and specification of the prototype passive house, namely timber
frame and concrete block2. It is demonstrated below that the Passivhaus
Standard can be easily achieved in
Ireland using both of these construction
methods and that there are no major
advantages of one method over
another in terms of thermal performance. Both passive house construction
types can be built using mostly conventional materials as can be seen from the
detailed wall sections provided in
section 3.1.3.
3.1.1 Combining Aesthetic and
Energy Performance in House
The design of a passive house is strongly
influenced by the need to minimise heat
loss through the building fabric, to
maximise solar gains and to cater for the
various building services. Form and
function played equal roles in the design
of the passive house. The overriding
principle used in the design of the house
was that it should be broadly similar in
character to a conventional house, thus
maximising ease of acceptance to the
current housing market in Ireland.
As has been described in some detail in
the preceding sections, much of the ‘free’
energy required to heat a passive house
comes directly from the winter sun
through south facing windows. It is therefore typical (though not essential) to have
a bias in terms of placement of glazing on
the southern elevation. Combined with
such glazing is the need to prevent
overheating in summer and this is easily
ensured through the use of shading, in this
case with a balcony and pergola. The walls
of a passive house are typically thicker
than those of conventional construction
due to the need for additional insulation
and this must be borne in mind in the early
stages of design development. Another
key issue to consider when developing the
design of a passive house is the need to
minimise thermal bridging including that
created between the foundation and internal walls, for example. Bearing in mind the
above principles of glazing orientation,
wall thickness and minimised thermal
bridging, the designers commenced the
development of the prototype passive
The prototype house presented below
would achieve a BER rating of A2.
Should an A1 BER rating be desired,
one method of achieving this would
be to improve the U value of the
opaque elements of the entire building envelope from 0.15 W/(m2K) to
0.10 W/(m2K), increase the area of
solar panels from 7.5m2 to 10.0m2,
increasing the efficiency of the
heating system from 80% to 85% and
adding approximately 7m2 photo
voltaic panels. There would be other
methods of improving the BER rating
other than those specified above.
Furthermore, it has to be highlighted
that not all buildings designed to the
Passivhaus Standard would achieve an
A2 or A1 rating. The example below
has been especially designed to
achieve both a good BER rating as well
as meeting the Passivhaus Standard,
using both DEAP and PHPP.
3.1.2 Decision Support using Passive
House Planning Package (PHPP)
The Passive House Planning Package
(PHPP V2007) has been introduced
already in these guidelines. It is an Excelbased software that can be used to ‘test’
the energy performance of a building as
it is being designed. It includes Irish
climatic data which is useful in ensuring
that buildings are not over-specified in
terms of thermal performance. Key
aspects of the emerging prototype
passive house are entered into the
software with a view to ensuring that
the design achieves the minimum
requirements of (a) space heating delivered energy demand of 15 kWh/(m2a)
treated floor area (TFA3), and (b) upper
limit for total primary energy demand
page 31
for space and water heating, ventilation,
electricity for fans and pumps, household appliances, and artificial lighting
not exceeding 120 kWh/(m2a), regardless of energy source.
The thickness of insulation required in
the walls, floor and roof is evaluated and
guided by the PHPP software, as is the
specification and positioning of the
windows, the sizing of the back-up space
heating system, the consideration of
thermal bridges and many other aspects
of the design including ventilation provisions. The design is thus an iterative
process. Different insulation types can be
tested in the software, with higher
performance materials (in terms of lower
Lambda values) requiring thinner walls
than other less efficient materials.
ing. In both cases, the maximum space
heat requirement of 15 kWh/(m2a) has
been achieved.
Two extracts from the PHPP software are
included below for both the timber
frame and masonry construction prototypes in order to give an insight into how
the software can be used to assist the
designer. The first extracts comprise the
so-called ‘Verification’ page which
summarises the performance of both
construction types in terms of such critical matters as space heat demand,
confirmation of blower door test results,
specific primary energy demand,
heating load and frequency of overheat-
The second extracts provide an insight
into how the U-values of major building
elements are calculated for both timber
frame and masonry construction types.
The table provide details on how the
required U-values have been achieved
for walls, floors and ceiling. The partial
thermal bridge caused by the timber
studs in the timber frame option is
accurately calculated in the software by
specifying the proportion of the
insulated wall occupied by timber (in
this case 10%).
Passive House Verification for the prototype passive house, concrete block construction.
Source: MosArt Architecture.
page 32
IFC, Insulated Concrete Forms.
Source: UCD Energy Research Group.
Externally insulated concrete block wall.
Source: MosArt Architecture.
Passive House Verification for the prototype passive house, timber frame construction.
Source: MosArt Architecture.
page 33
U-value of building elements for the prototype passive house, concrete block construction. Source: MosArt Architecture.
page 34
U-value of building elements for the prototype passive house, timber frame construction. Source: MosArt Architecture.
page 35
Cross section, prototype passive house. Concrete block construction. Source: MosArt Architecture.
page 36
Cross section, prototype passive house. Timber frame construction. Source: MosArt Architecture.
page 37
3.1.3 Prototype Passive House
External Wall Sections
The wall sections for both construction
types have been illustrated previously. It
should be noted that no dimensions are
included on the sections below as they
are intended to be schematic only. They
should not be used as a basis for
detailed construction drawings.
The following key issues can be noted
from the detailed wall sections:
Thicker than normal wall sections
are designed in order to accommodate the required depth of insulation. There is also substantial insulation used in both the roof and under
the floor.
The insulation at the junction of roof
and wall, as well as wall and floor,
overlap in order to minimise thermal
bridging at these critical locations.
The window frame is also partly
bedded in insulation in order to
reduce heat loss.
Membranes and specialist tapes are
used to create an airtight envelope.
This is especially critical at junctions
between different elements, such as
around windows, and also where the
first floor penetrates the external
A service cavity is proposed, internal
to the airtight layer in the timber
frame wall, in order to accommodate
mechanical and electrical fittings. A
similar cavity is proposed in the
underside of the ceiling at first floor
level for both house types.
Special blockwork with low thermal
conductivity is used in the rising
walls to reduce thermal bridging
between foundations and walls.
3.1.4 Prototype Passive House
Design including Mechanical
and Electrical Services
The final design of the prototype passive
house is presented below in plan, elevation, section and, finally, a 3D model. A
number of mechanical and electrical
features are highlighted which have
been included specifically in the development of the passive house prototype:
In terms of mechanical ventilation,
an average air flow rate of approxi-
page 38
mately 115 m3/h would be required,
representing an approximate air
change rate of 0.4 per hour. A fresh
air outlet is provided to the living
room, dining room, double height
sun room (at ground floor level) and
bedrooms whereas an extract vent is
provided in WC’s and bathrooms as
well as the kitchen, the utility room
and the upper part of the sun room.
The heat recovery ventilation unit is
located in the utility room and will
recover the majority of the heat from
the extracted air to warm the incoming fresh air. An airing cupboard is
located on the first floor along with
the washing machine. This space is
connected to the ventilation system
and can function as drying cabinet
for drying clothes in the winter.
Sound attenuators should be used in
order to minimise noise travelling
along ducts and air filters should be
changed as required in order not to
compromise indoor airflows and / or
air quality.
A pellet stove is proposed for the
backup space and water heating
system4. For the prototype house the
annual space heat requirement
(without losses of the heating
system) is 13 (kWh/m2a). Including
the losses the final energy is 26
(kWh/m2a) equating to approximately 2,860 kWh over an entire year
(the house measures 110m2 in
treated floor area). This would
equate to 269 litres/year of oil, 277
m3/year of mains gas or 572 kg/year
of wood pellets (in bags).
The design or peak heat load, on the
other hand, is approximately 1,800
W, or just 1.8 kW. This amount of
energy could be provided by a very
small stove / heater incorporating a
back boiler, or by a small separate
boiler compared to what might be
typically required in a family home;
there are several such ‘small’ heating
appliances on the market which
range in output from 2.4 to 8kW,
with an efficiency of up to 80%.
The pellet stove in the prototype
house has been positioned in the
sitting room, but space has also
been left in the utility room as this
might be preferable to users. Care
must be taken to use a stove that
delivers most of the heat output to a
hot water tank which can be used
not only for domestic hot water but
also as a ‘buffer’ to work in tandem
with a water to air heat exchanger
(see below). A stove that only emits
radiant heat directly into the room in
which it is located would likely
overheat that same room due to the
high levels of insulation required in a
passive house.
The pellet stove can be filled
manually as the need arises, or could
be automatically fed using an underground pellet storage ‘bunker’
located underground to the public
road side of the house for ease of
delivery. While a house of this size
could probably manage without an
automatic feed from a bunker (given
an average use of approximately 40
kg of pellets per week5), the advantage of such a system is in the space
saved from having to store pellets in
the house or garden shed. In
positioning the pellet stove in the
sitting room, there is a perceived
aesthetic benefit to be gained from
visibility of the flames coupled with
the delivery of some heat directly
into the sitting room.
It is also critically important that the
pellet stove has its own independent
fresh air supply, given the airtight
nature of the construction, and that
there is an appropriate flue for
venting of exhaust gases. Such
systems are commonplace in passive
houses and confer both an efficiency
and a safety benefit that will not
adversely affect the balanced ventilation system.
The large domestic hot water tank
(1,000 litre), which serves as a ‘buffer’
heat store as indicated above, is
located adjacent to the mechanical
ventilation unit, in the utility room.
The backup heating system in this
case is provided by heating the fresh
air circulating around the house
from the hot water in the ‘buffer’
tank using a water to air heat
exchanger. In this regard, all supply
air ducts should be insulated in
order to minimise heat losses, even if
they are located within the thermal
Solar panels (measuring 7.5m2) are
positioned on the south facing roof
which is pitched at the optimal angle
of 45 degrees. These have been sized
in accordance with the needs of such
a house and could include either flat
plate collectors or evacuated tubes.
Other aspects of the design which are
not related to the mechanical or electrical services are listed below:
All windows in the prototype house
are triple glazed with low emissivity
coating, thermally broken frames
and gaskets especially designed to
minimise air infiltration. A passive
house triple glazed window is
typically three to four times more
energy efficient than a standard
double glazed unit and, if approximately south facing, will take in
more energy in a year than it lets out.
The use of such glazing ensures high
thermal comfort in cold weather
through minimal temperature difference between the internal glass
pane surface and room temperature.
A balcony is provided at first floor
level, the primary function of which
is to shade the extensive area of
glass on the south elevation. This
balcony can be accessed via the
gallery which overlooks the doubleheight sun room. A wooden pergola
is provided overhead the balcony to
shade the upper storey windows. A
possible alternative to this pergola
could be a deep roof overhang but
the steepness of the pitch in the
prototype house would mean that
this latter solution would restrict
high level views from the upper
The internal party walls can be
constructed as per a conventional
house as long as it is within the
boundaries of the building
The hatch to the attic should be very
well insulated and completely
airtight to minimise cold air infiltration.
Ceiling insulation is placed horizontally on the attic floor in the prototype passive house. It would also be
possible to place this insulation
between the rafters, albeit with
design and construction implications.
The timber frame option depicted in
these guidelines is ventilated with
an external cavity.
Energy efficient light fittings should
be used which use less primary
energy (they will also reduce internal
heat gains). It is also recommended
to use energy efficient household
appliances for cooking, wet appliances, cold appliances etc. to enable
the primary energy performance
target of 120 kWh/(m2a) to be met.
Various building methods can be used in
the construction of a passive house,
including insulated concrete formwork
and externally insulated concrete block
wall, shown below. This is in addition to
the more common masonry and timber
frame construction methods, as illustrated in the prototype house examples
shown above.
thermal bridging) with the remaining
40% covering building systems including MHRV, solar thermal system, wood
pellet boiler and low energy lighting.
Gardiner and Theobald next sought to
express the additional passive house
costs as a proportion of conventional
construction costs. The cost of a conventional house varies considerably according to the quality of finishes required. An
average cost of €196,000 was proposed
as representing a mid-grade finish,
including VAT and design fees. The
additional €25,000 thus represents
approximately 12.5% of conventional
build costs.
3.2 Cost Considerations
An analysis of additional costs associated with construction of the prototype
house to the Passivhaus Standard was
carried out by Gardiner and Theobald,
Quantity Surveyors. The additional cost
of the key items including enhanced
insulation, glazing, airtightness and
thermal bridging was estimated, along
with the cost of such technologies as
MHRV, solar panels for DHW, a pellet
stove as well as energy efficient light
bulbs and household appliances.
Included in their analysis was an
allowance for the foregone costs associated with ‘conventional’ house features
such as a fireplace and boiler with radiators. Gardiner and Theobald completed
their analysis for both the timber frame
and the concrete block construction
The additional ‘extra over’ cost associated with building the prototype house
to the Passivhaus Standard was
estimated at approximately €25,000 for
both construction types, including VAT
and design fees (referring to 2007 building costs). Approximately 60% of this
cost can be attributed towards improvement of the building shell (enhanced
insulation, higher grade windows,
improved airtightness and reduced
Approximately 17% of the overall
housing stock in Ireland are semidetached dwellings.
According to the Irish Timber Frame
Manufacturers’ Association (ITFMA) the
number of timber frame house completions has grown from a market share of
15% in 1999 to a market share of 30% in
The TFA is the living area within the
thermal envelope. Any rooms or areas
beyond the boundaries of the thermal
envelope are not considered.
Other sources of heat such as gas or heat
pumps can also be used.
Estimated heating requirement for hot
water (net of 60% SWH) + space heating
= 6,300 kWh = c.1,260 kg pellets/year =
40 kg/week over a 30 weeks heating
Passive House Planning Package, PHPP
2004, Technical Information PHI2004/1(E). Darmstadt, Germany.
Passive House Institut, Dr. Wolfgang
page 39
Prototype passive house, floor plans (not to scale). Source: MosArt Architecture
page 40
Prototype passive house, floor plans (not to scale). Source: MosArt Architecture
page 41
Prototype passive house, cross section (not to scale). Source: MosArt Architecture
page 42
Prototype passive house, front, back and side elevations (not to scale). Source: MosArt Architecture
page 43
Prototype passive house, 3D model (not to scale). Source: MosArt Architecture
page 44
Sustainable Energy Ireland
Renewable Energy Information Office
Unit A, West Cork Technology Park
Co Cork
T. +353 23 63393
F. +353 23 63398
[email protected]
SEI is funded by the Irish Government under the
National Development Plan 2007 - 2013 with
programmes part financed by the European Union.
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