Your Guide to Building an Energy Efficient Home

Your Guide to Building an Energy Efficient Home
The energy for life…
Energy is essential to our daily lives. It heats our homes, fuels our transport and supplies
our electricity. At the moment, most of the energy we use comes from fossil fuels such as
oil, gas, coal and peat. Unfortunately there is a limited supply of fossil fuels in the world
and we are using them up at a very fast rate. The other downside to fossil fuels is that
burning them for energy also produces CO2, a greenhouse gas, which causes climate
change. That’s where sustainable energy comes in.
So what is sustainable energy?
Sustainable energy refers to a way we can use and generate energy that is more efficient
and less harmful to the environment. Another way of explaining sustainable energy is
that it will allow us to meet our present energy needs without compromising the ability
of future generations to meet their own needs. We can do this by being more efficient in
how we use energy in our daily lives and also by increasing the amount of energy that
comes from renewable sources such as the wind, the sun, rivers and oceans.
What are the benefits of sustainable energy?
The good news is that being sustainable in how you use energy has immediate benefits:
It will save you money on your electricity and heating bills
Your home will be more comfortable and convenient
And you will also be making a vital contribution to reducing climate change
Believe it or not, the small actions you take to be more energy efficient in your home can
have a very significant impact on improving the environment. The collective efforts of
individuals can often be the most powerful of all.
Who is Sustainable Energy Ireland?
Sustainable Energy Ireland (SEI) was set up by the government in 2002 as Ireland’s
national energy agency with a mission to promote and assist the development of
sustainable energy. SEI’s activities can be divided into two main areas:
Energy Use - Energy is vital to how we live our daily lives but most of us don’t use
energy as efficiently as we could. By assisting those who use energy (mainly industry,
businesses and householders), to be more energy efficient, SEI can help to reduce the
amount of energy we use overall.
Renewable Energy - Energy that is generated from renewable sources such as wind
and solar power is clean and doesn’t produce harmful greenhouse gases. By
promoting the development and wider use of renewable energy in Ireland SEI can
help to further benefit the environment, in particular reducing the threat of climate
SEI is also involved in other activities such as stimulating research and development,
advising on energy policy and producing energy statistics.
Sustainable Energy Ireland is funded by the National Development Plan 2000-2006 with
programmes part financed by the European Union.
Did you know…
Energy use is responsible for two-thirds of Ireland’s greenhouse gas emissions.
Irish homes use around a quarter of all energy used in the country– that’s
even more than industry.
The average home consumes almost 40% more electricity than it did in 1990.
Renewable energy currently accounts for just 2% of Ireland’s energy supply.
Planning & Building an Energy Efficient Home
While the Building Regulations require
that new buildings achieve minimum
standards of energy efficiency, higher
levels are in many cases worthwhile.
Since a house being built today can be
expected to be occupied for 60 years or
more, an energy-efficient design can yield
considerable savings over its lifetime.
Although some energy-saving measures
can be implemented at a later stage,
retrofitting is often more expensive and
less effective than incorporation when
the house is being built.
Apart from reducing fuel and electricity bills, an energy-efficient home design can
provide improved comfort for occupants while helping to protect the environment.
It can also provide insurance against future increases in fuel costs.
This leaflet aims to provide tips on energy efficiency to those planning to build (or
buy) a new home. It is not comprehensive – the range of details for energy-efficient
house design is too wide for that.
Fundamental Planning Decisions
Site selection
Energy used in driving from place to place can amount to a significant proportion
of a household’s total energy consumption. By locating new houses near to workplaces, schools, public transport routes, etc., transport energy consumption can be
Transmission of sunshine through windows (passive solar heating) can reduce
heating costs.The selection of a site which is exposed to the low-altitude winter sun
can allow for passive solar heating.
By selecting a location sheltered from the wind, heat loss from the building can be
reduced. Shelter can be provided by nearby trees, adjacent buildings or surrounding
hills. If no such shelter exists, it can be provided in time through planting trees or
Winter Sun
In some, mainly rural, locations there may be potential for renewable energy sources
other than solar, for example hydropower, wind power, wood, biogas, or heat which
can be extracted from the ground or sea. The possibility of obtaining heat from a
combined heat and power plant or group heating scheme may also influence the
selection of a site.
Building form and orientation
A compact building form of minimum surface-to-volume ratio is best for reducing
heat loss. However, a rectangular building with one of the longer facades facing
south can allow for increased passive solar heating, day-lighting and natural
ventilation. As well as reducing energy costs, sunny south-facing rooms also have
high amenity value.
Projections such as bay and dormer windows should be kept to a minimum, since
by increasing the surface-to-volume ratio of the building, they will increase heat
loss. They also tend to be more difficult to insulate effectively.
Pitched roofs should have one slope oriented south to allow for optimum
performance of a roof-mounted or roof-integrated active solar heating system. Even
if such a system is not planned during construction, it may be installed at some
stage during the life of the building.
Energy assessment
Many decisions affecting the energy performance of a house are taken early in the
design process. A method of calculating annual heating energy consumption
should be used to compare alternatives at the preliminary design stage.
Building Fabric and Structure
Levels of insulation higher than those required in the Building Regulations are in
many cases economically justified. Insulation should be well distributed around the
building shell. It is better to have a good overall level of insulation than, for example,
a highly insulated floor with no roof insulation.
Attention should be given
to the avoidance of thermal
bridges. These are “short
circuits” across insulation,
which are commonly found
at lintels, jambs and sills of
doors and windows, and at
junctions where floors and
ceilings meet external walls.
They give rise to increased
heat loss and possible
condensation problems.
Thermal Bridge
There are many examples of buildings performing more poorly than expected in
energy terms due to poor quality workmanship in installing insulation. To achieve
the level of energy efficiency predicted by the design, it is very important to ensure
good quality workmanship and supervision during construction.
Adequate ventilation is essential to provide fresh air and to remove moisture,
odours and pollutants. However, excessive ventilation during the heating season
results in energy wastage and can also cause discomfort due to draughts.
Controlled vents should be installed in every room; trickle or slot vents incorporated
in window frames can ensure a reasonable amount of continuous fresh air and can
be opened up or closed down to a minimum as required.
Cooker hoods and small fan exhausts allow for controlled removal of moist air from
kitchens and bathrooms, and prevent this air being drawn into living or bedrooms.
Attention should be given, during both design and construction, to ensuring that
the building is well sealed. Services should be designed with minimum penetration
of pipework and cabling through the building’s insulated shell. Doors and windows
should come with factory-applied draught seals. Porches and draught lobbies can
reduce draughts at external doors.
Never seal up a house completely, as a minimum of fresh air is required for health
and safety reasons.
If an open fire or other fuel-burning fireplace appliances are to be installed, they
should have an independent air supply. This can be achieved by means of an
underfloor draught or by using a room sealed appliance such as a balanced flue
A balanced ventilation system involving fans, ductwork and a heat exchanger can
transfer heat from warm stale outgoing air to incoming fresh air (this is called
“mechanical ventilation with heat recovery”). Stale air is usually extracted from
rooms such as kitchens and bathrooms, and warmed fresh air supplied to living
rooms and bedrooms.
For such systems to work well,
the house must be well sealed.
Correctly sized systems can
reduce ventilation heat loss
If the house is to be built in an
area where leakage of radon
gas from the ground gives rise
to concern, appropriate steps
should be taken to prevent
its entry into the house.
The Radiological Protection
Institute of Ireland can advise
on this.
Heat Exchanger
Cooled Stale Air
Cold Fresh Air
Stale Air
Fresh Air
Passive solar features
If the house is exposed to the low-altitude winter sun, glazing should be
concentrated on the south facade. Window area on the north facade should be
minimised to limit heat loss. Thermal mass within south-facing rooms, e.g. masonry
walls or concrete floors, can absorb and store solar energy during the day and
release it gradually during the evening. The heating system should have a fast
response time and good controls to maximise the usefulness of solar gains.
Overheating protection in south-facing rooms in summer can be provided by
overhanging eaves, blinds, natural ventilation, thermal mass or other means.
In general, it is not wise to increase
south-facing glazed areas too
dramatically. Otherwise additional
measures will be required to avoid
overheating in summer and
excessive heat loss at night and on
overcast days in winter.
Windows should have a high
resistance to heat loss. ‘Lowemissivity’ double glazing, which has a special coating to reduce heat loss, is
Well-fitting curtains can help to retain heat at night. If a radiator is mounted below
the window, the curtains should not cover it when closed, but should rest lightly on
a window-board or shelf above the radiator. This arrangement will direct warm air
from the radiator into the room rather than up behind the curtain.
A well-designed sunspace or conservatory on
the south side of a building can reduce the
heating needs of a house by acting as a buffer
against heat loss and collecting solar energy
on fine days. However, there are many
examples of sunspaces, poorly designed from
an energy point of view, which increase
heating requirements. Sunspaces should not
be heated, and should be separated from the
heated space by walls and / or closable doors /
windows. They should not be regarded as
being habitable all year round. The energy
losses from one heated sunspace can negate
the savings of ten unheated ones!
Insulation or
reflective foil
Building materials
The embodied energy of a product is the energy used to produce it, and includes
energy used in extracting raw materials, processing and transport, e.g. Irish-grown
timber will incur lower transport energy use than timber imported from overseas.
The embodied energy of a house is typically over five times its annual energy
consumption and therefore equates to approximately 5-10% of the total energy
consumption during the life of the house.
The building materials selected should have minimum environmental impact
during their entire life cycle, including manufacture, use and disposal. Building
components should be designed for long life and durability, and ideally should be
recyclable at the end of their operating lives.
Heating systems
Energy efficient houses need smaller heating systems than conventional houses.
The resulting savings will help to pay for the cost of additional insulation.
The heating system should be efficient, not only at full load, but also at lower loads.
If looking at oil or gas boilers, you should ensure that the boiler complies with the
EU boiler efficiency directive. In the case of gas boilers, you should consider
condensing boilers, which cost a bit more but are highly energy-efficient.
If selecting individual room heaters, consider room sealed, balanced flue units.
Room heaters should be correctly sized for the room they are to heat and should be
thermostatically controlled.
Hot water systems
It is generally more energy-efficient to heat water using an efficient boiler or other
fuel-burning appliance than with an electric immersion heater. The hot water
cylinder should be well-insulated; factory applied insulation is generally more
effective and durable than a lagging jacket. As well as providing space heating,
combination ‘combi’ boilers supply hot water directly to the taps, thus avoiding the
losses associated with storage in a hot water cylinder.
By locating the heating and hot water systems, including pipework, entirely within
the insulated building shell, heat losses can become heat gains. Ensure good
ventilation to the boiler and take account of fire regulations. Attention should be
given to minimising the lengths of pipe runs and associated heat losses.
Automatic controls
Heating system controls should be installed to ensure that heat is provided only
when and where it is needed. The Building Regulations require thermostatic
radiator valves that allow control of temperatures in individual rooms. Separate time
and temperature control in two or more zones is necessary where floor area is
greater than 100m2.
Open fires
Open fires, whether of the solid fuel or gas type, are wasteful of energy, and even
when they are not in use, the chimney gives rise to uncontrolled ventilation heat
loss. If a fireplace must be installed, an ‘underfloor draught’ air supply (a small duct
or pipe installed within the floor and connecting the outside air directly to the
fireplace) can help to reduce the amount of warm internal air escaping through the
chimney. A closed stove is preferable to an open fire in terms of controlled efficient
Active solar heating systems, including a solar collector on a south-facing roof, can
contribute to heating needs.
A solar water heating system can
provide about 60% of a family’s
annual hot water requirement,
with back-up heating coming
from the conventional system.
A solar space heating system
can contribute to heating needs,
particularly in spring and
autumn. Though the economics
of such systems may be marginal
at present low fuel prices, they
use a clean, sustainable energy
solar collector
Hot water cylinder
To taps
Lighting and Appliances
Energy-efficient lamps and fittings should be chosen for all
rooms where lights are likely to be switched on for long periods
- living rooms, kitchens, halls,
security lighting etc. While a
compact fluorescent lamp
(CFL) costs more to buy than
an ordinary tungsten bulb,
More Efficient
the energy savings it will
yield will more than recoup the investment over
its long operating life.
All fridges, freezers, washing machines and
tumble dryers on display in shops are now
required by law to display Energy Labels
indicating their energy efficiency. These labels
can assist the purchaser in selecting an energyefficient model.
Less Efficient
Energy Consumption kWh/year
(Based on standard test results for 24 h)
Actual consumption will
depend on how the appliance is
used and where it is located
Fresh food Volume 1
Frozen food Volume 1
(dB(A) re 1 pW)
Further information is contained
in product brochures
Norm EN153 May 1990
Refrigerator Label Directive No.94/2/EC
Complete package
The heating energy performance of a new building design can be predicted using a
standardised energy rating method.The result is usually expressed in kilowatt-hours
per square metre of floor area per year (kWh/m2y). According to the HER method, a
typical house just satisfying the 2002 Building Regulations will have a rating of
about 90 kWh/m2y. However, it is possible to achieve a fuel consumption less than
this value through measures referred to in this leaflet.
From early 1997, the Technical Guidance Document L to the Building Regulations
will incorporate a provision whereby an energy rating procedure can be used to
demonstrate compliance.
Householder manual
The energy consumption of a house depends nearly as much on the behaviour of
occupants as on the building design. While the former is beyond the control of the
designer, he/she can provide guidance to occupants on energy-efficient operation
of the house through a user’s manual, personal instruction, or both. This guidance
could include topics such as the use of timers, control of ventilation, servicing of
heating system, energy-efficient cooking tips, etc.
High standards of energy-efficient building design have been demonstrated in
many recently-constructed housing projects in Ireland, including 400 low-energy
houses built around Ireland with co-funding under the EU THERMIE programme.
Some of these have active solar heating systems.
Relevant Standards
Building Regulations, 2002
Part L: Conservation of Fuel and Energy
Part F: Ventilation / Part J: Heat Producing Appliances.
ISEN 832 - Thermal performance of buildings - calculation of energy use for building
- residential buildings CEN 1998.
Useful contacts for further information
For information on energy efficiency measures
SEI, Glasnevin, Dublin 9.
For information on solar heating systems
Energy Research Group, School of Architecture, U.C.D., Richview, Clonskeagh, Dublin 14.
SEI, Renewable Energy Information Office, Shinagh House, Bandon, Co. Cork.
For information on radon gas
Radiological Protection Institute of Ireland, 3 Clonskeagh Square, 119 Clonskeagh
Road, Dublin 14.
Useful publication
Green Design: Sustainable Building for Ireland; Ann McNicholl and J. Owen Lewis
(eds), Energy Research Group, University College Dublin; Office of Public Works,
Source Text
Energy Research Group UCD
This leaflet is printed on paper produced from 50% recycled
and de-inked fibres and 50% chlorine free bleached pulp (TCF).
Read our other publications:
A Detailed Guide to Insulating Your Home
A Detailed Guide to Home Heating Systems
Your Guide to Renovating an Older Home
Your Guide to Renewable Energy
A Consumer Guide to Sustainable Energy
How to make your Home more Energy Efficient
Sustainable Energy Ireland is funded by the
Irish government under the National
Development Plan 2000-2006 with programmes
part financed by the European Union.
SEI, Glasnevin, Dublin 9
tel: +353 1 836 9080
fax: +330 1 837 2848
[email protected]
SEI InfoLine
8 to 8, Mon to Fri, 1850-376 666
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