Guide to Attic Air Sealing - Structure Tech Home Inspections

Guide to Attic Air Sealing - Structure Tech Home Inspections
GUIDE TO ATTIC AIR SEALING
IDENTIFYING AND BLOCKING AIR LEAKAGE PATHWAYS
PROVIDING AIRTIGHT CLOSURE
Attics should be air sealed prior to adding insulation. Adding insulation alone does not save
much energy and can lead to health and durability problems. The intent of this guide is to provide
information for the preparation work necessary prior to adding attic insulation.
Inspect the House
Do Not Proceed If:
Inspect the work area, check for combustion appliances,
controlled ventilation, and required attic ventilation. Develop the
work plan. See page 3 and Appendix A.





The house attic has active knob and tube wiring
The house attic has vermiculite insulation
The house attic has bathroom fans vented into the attic
The house has a leaking roof
The house has an unvented kerosene heater or gas fireplace
1. Combustion Safety
Combustion air is required. If you have gas or oil-fired furnaces
or gas or oil-fired water heaters or boilers that have natural draft
chimneys combustion air supplied directly from the outside is
required. Test for backdrafting. The best approach is to replace
natural draft appliances with sealed combustion, induced draft or
power-vented furnaces, boilers and water heaters. Install carbon
monoxide detectors. See page 5.
2. Ventilation for Indoor Air Quality
Controlled ventilation is required. As a minimum, houses require
an exhaust, supply or balanced controlled mechanical ventilation
system. See page 10.
3. Attic Ventilation for Durability
Attic Ventilation is required. All roofs must be vented according
to the applicable building code. See page 12.
4. Air Seal the Attic
Follow the details provided in this Guide. See page 15.
5. Then Insulate
Install according to manufacturer’s instructions, including all
safety, performance and quality assurance requirements.
FOREWORD
Guide to Attic Air Sealing
The guide to Guide to Attic Air Sealing provides information and
specifications to the following groups:
-
Home remodelers
Builders
Insulation contractors
Mechanical contractors
General contractors who have previously done remodeling
Homeowners as a guide to the work that needs to be done
The order of work to be done during home improvements is important.
Health and safety issues must be addressed first and are more important
than durability issues. And durability issues are more important than saving
energy.
Even though the purpose of this guide is to save energy – health, safety
and durability should not be compromised by energy efficiency.
Accordingly, combustion safety and ventilation for indoor air quality are
addressed first. Durability and attic ventilation then follow. Finally, to
maximize energy savings, air sealing is completed prior to insulating.
This guide is prescriptive-based to minimize risks. Enhanced performance
and greater energy savings are possible with performance-based
approaches.
Performance-based approaches should build on the
measures and specifications contained in this guide.
Not all techniques can apply to all houses. Special conditions will require
special action. Some homeowners will wish to do more than the important
but basic retrofit strategies outlined by this guide. Where possible
throughout the manual, links have been made to “performance” path
solutions that require the judgment and experience of design professionals
and specialist skills and experience.
Written by:
Note: For homeowners and contractors
unfamiliar with working in attics, the following
safety issues should be addressed:
a.
Be aware of head injury, especially
nails in sheathing below roof.
b.
Wear proper personal protective
equipment such as a mask for avoiding
breathing in excessive dust and long
sleeves to avoid skin irritation.
c.
Be prepared to walk among difficult
obstacles along narrow walking boards
or on ceiling joists with minimal hand
holds. Do not step on insulation or
gypsum board ceiling.
d.
Be aware that you are working in a
confined space, ensure that adequate
ventilation is available.
Joseph Lstiburek, Ph.D., P.Eng.
Building Science Corporation
30 Forest Street
Somerville, MA 01243
(978) 589-5100
www.buildingscience.com
Acknowledgements
The author would like to acknowledge the funding and support of the US Department of
Energy’s Building America Program. This Guide is the product of a collaborative effort.
Special thanks to Stephanie Finnegan, Bohdan Boyko, Ren Anderson and Alex Lukachko.
Notice
This report was prepared as an account of work sponsored by an agency of the United States
government. Neither the United States government nor any agency thereof, nor any of their
employees, makes any warranty, express or implied, or assumes any legal liability or
responsibility for the accuracy, completeness, or usefulness of any information, apparatus,
product, or process disclosed, or represents that its use would not infringe privately owned
rights. Reference herein to any specific commercial product, process, or service by trade
name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its
endorsement, recommendation, or favoring by the United States government or any agency
thereof. The views and opinions of authors expressed herein do not necessarily state or reflect
those of the United States government or any agency thereof.
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2
INSPECT THE HOUSE
Guide to Attic Air Sealing
Inspect the House
Before any air sealing work is done, inspect the work area. Check first for
active knob and tube wiring, vermiculite insulation, bathroom fans vented
into attics, leaking roofs, and unvented kerosene heaters or gas fireplaces.
Note on Vermiculite: this insulation may be
contaminated with asbestos. For more
information, see:
www.epa.gov/asbestos/pubs/verm.html
STOP WORK – do not proceed:
IF the house attic has active knob and tube wiring.
THEN the house must be rewired prior to the attic being air
sealed and insulated.
IF the house attic has vermiculite insulation.
THEN professional advice should be obtained. The
vermiculite insulation may contain asbestos and must be
tested prior to the attic being air sealed and insulated. Contact
your State Department of Health.
IF the attic has bathroom fans vented into the attic.
THEN bathroom fans must be vented to the outside prior to
the attic being air sealed and insulated.
IF the house has a leaking roof.
THEN the leaking roof must be fixed prior to the attic being air
sealed and insulated.
IF there is an unvented kerosene heater or gas fireplace.
THEN the unvented heater or fireplace must be vented or
removed prior to the attic being air sealed and insulated.
Check next for combustion appliances, controlled ventilation, and required
attic ventilation. The following health, safety and durability issues must be
addressed:
1. Combustion Safety.
If you have gas- or oil-fired furnaces or gas- or oil-fired water heaters that
have natural draft chimneys, combustion air supplied directly from the
outside is required. If natural draft gas or oil appliances are present and a
dedicated source of combustion air supply from the outside is not present,
then a qualified mechanical or plumbing contactor in the State must be
engaged to provide this source of combustion air. Carbon monoxide
detectors are required to be installed if the house has combustion
appliances.
Definition – Combustion Air: the air
provided to fuel-burning equipment including
air for fuel combustion, draft hood dilution
and ventilation of the equipment enclosure
(IRC 2009 Section R202). Also see:
www.cpsc.gov/cpscpub/pubs/452.html
The best approach is to replace natural draft appliances with sealed
combustion, induced draft, or power-vented furnaces, boilers, and water
heaters. They are significantly more energy efficient than natural draft
appliances and, when installed according to manufacturers installation
instructions, they do not require a duct supplying outside combustion air as
described here.
More information about Combustion Safety for oil and gas appliances is
provided in this Guide on page 5.
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3
INSPECT THE HOUSE
Guide to Attic Air Sealing
2. Controlled Ventilation for Indoor Air Quality.
At a minimum, houses require an exhaust, supply or balanced controlled
mechanical ventilation system. If a controlled mechanical ventilation
system is not present, one should be installed by a qualified contractor.
Definition – Controlled Ventilation: The
process of supplying outdoor air to or
removing indoor air from a dwelling by a fan
or fans. See example on page 10.
More information on Controlled Ventilation options is provided in this Guide
on page 10.
Reference – ASHRAE Standard 62.2 –
2010: Ventilation and Acceptable Indoor Air
Quality in Low Rise Residential Buildings
3. Attic Ventilation for Durability.
All roofs must be vented according to the applicable building code. If the
roof is not vented according to the applicable building code then a qualified
contractor in the State should be engaged to install the necessary venting.
More information on Attic Ventilation for houses with and without soffit vents
is provided in this Guide on page 12.
Air Seal the Attic
Once the issues identified above have been addressed, proceed to develop
the attic air sealing work plan. Air sealing details for most common attic
situations are provided in this Guide on page 15. A sample work plan can
be found in Appendix A.
Definition – Attics: The space between the
underside of the roof deck sheathing and the
topside of the top story ceiling. This space
does not include cathedral ceilings.
Definition – Attic Ventilation: The
intentional flow of outdoor air into an attic
space balanced by the intentional flow of
attic air to the outside by natural means. The
primary function of attic ventilation is to
control moisture accumulation and ice dam
formation (in certain climates).
Other Guides for air sealing are available. The Guide to Attic Duct Sealing
provides important information for houses with ductwork and other
mechanical system components located in the attic. If applicable,
information from the other Guides should be considered when developing
the attic air sealing work plan.
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4
1. COMBUSTION SAFETY
Guide to Attic Air Sealing
Air Sealing, Combustion Air and Saving Energy
Energy is saved when holes between conditioned areas and
unconditioned attics are sealed even if a necessary hole is then added
to supply combustion air. The logic is both intuitive and counter-intuitive.
First, in most houses the surface area of holes sealed in the attic will be
much greater than the surface area of the hole added to provide
combustion air. The house, therefore, ends up with fewer holes.
Note: There are some important openings that
should not be sealed. Combustion air ducts
and soffit, ridge and gable vents are all
intentional openings that must be kept open to
air movement in order to work properly.
Second, not all holes are alike. Holes up high leak more air than holes
down low. This is because houses are like hot air balloons that are too
heavy to leave the ground. A hole at the bottom of the hot air balloon
does not matter much, but a hole at the top of the hot air balloon matters
a great deal. Sealing a hole up high in an attic and then adding a hole of
equal size down near a furnace actually reduces air leakage and saves
energy.
Most importantly, sealing holes in attics makes chimneys work better. A
leaky attic ceiling acts like a chimney itself – and this “attic ceiling
chimney” competes with the real chimney for the same air.
Air sealing the leaky attic ceiling also reduces the “suction” of the house
on the ground under the house so less contaminants are drawn into the
house such as radon and other soil gases. The more air that leaves the
top of a house, the more air that is drawn (or sucked) in at the bottom of
a house. Sealing the top of a house reduces the entry of contaminants
and air at the bottom of a house – even if a hole is present at the bottom
of the house.
Consider Upgrading Existing Appliances
The best approach to combustion safety is to replace natural draft
appliances with sealed combustion, induced draft or power-vented
furnaces, boilers and water heaters. These types of appliances are
significantly more energy efficient than natural draft appliances and
when installed according to manufacturers installation instructions they
do not require a duct supplying outside combustion air as described
here.
If the House has Gas Appliances . . .
Gas-fired furnaces, boilers and water heaters that have natural draft
chimneys require combustion air. It should be supplied from the outside
by a duct. If these ducts are not sized correctly or if they are blocked
this can result in incomplete combustion of the fuel and can lead to
backdrafting. Backdrafting occurs when hazardous exhaust gasses
enter into the house rather than exit through the flue. The requirements
for gas appliances are slightly different than those for oil appliances.
Houses with appliances with natural draft chimneys, even if combustion
air is supplied directly from the outside, should be tested for
backdrafting.
Combustion safety – for more information,
see: www.cpsc.gov/cpscpub/pubs/452.html
and www.epa.gov/iaq/homes/hipcombustion.html
Additionally, if the house has combustion appliances, carbon monoxide
detectors complying with UL 2034 are required in close proximity to the
combustion appliances and outside each separate sleeping area in the
immediate vicinity of the bedrooms.
Reference – 2009 International Residential
Code For One- and Two-Family Dwellings:
Chapter 3 - Building Planning; Section R315
Carbon Monoxide Alarms.
Reference – 2009 International Fuel Gas
Code; Appendix D: Recommended Procedure
for Safety Inspection of an Existing Appliance
Installation.
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1. COMBUSTION SAFETY
Guide to Attic Air Sealing
Provide Combustion Air for Gas Appliances
A duct supplying outside combustion air is required for all natural draft
gas-fired furnaces and natural draft gas-fired water heaters. The size of
this duct is determined by the sum of the Btu input into both appliances
and TABLE 1 (below).
Note – Homes may have more than one
combustion air zone. In other words,
combustion appliances may be located in
more than one part of a house - in different
areas. Each zone needs to be treated
separately.
TABLE 1: Gas-fired Appliances – SINGLE OPENING TO OUTSIDE
Total input rating of all
Appliances in space
(Btu)
from
to
One Exterior Opening
Free Area (sq
in)
Duct Diameter
(in)
0
23,999
7
3
24,000
38,999
13
4
39,000
59,999
20
5
60,000
86,999
28
6
87,000
116,999
38
7
117,000
152,999
50
8
153,000
191,999
64
9
192,000
236,999
79
10
Reference – Gas Appliances: 2009
International Residential Code for One- and
Two-Family Dwellings; Chapter 24, Fuel Gas;
Section G2407 Combustion, Ventilation and
Dilution Air; G2407.6.2 One-permanentopening method.
Note: Combustion air openings must be
located away from combustion air exhaust
vents if there is a power vented appliance
along with a standard draft hood appliance.
NOTES: Openings to outside shall be located within 12" of top of enclosure. The "top of
the enclosure" refers to the ceiling of the room the appliances are located within.
The net free areas must take into account louvers and grilles if they are installed.
Assume 75% free area for metal and 25% for wood if the specific louver/grille
dimensions are unknown.
Exterior Wall
Combustion Air Supply
Attic Ceiling
Combustion Air Supply
Basement Wall
Combustion Air Supply
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1. COMBUSTION SAFETY
Guide to Attic Air Sealing
Clothes Dryers: Gas and Electric
Clothes dryers are powerful exhaust devices that typically exhaust 150
cfm of interior air to the outside. A make-up air opening of 100 square
inches is necessary for gas dryers and is recommended for electric
dryers where dryers are located in rooms or closets.
Reference – 2006 International Residential
Code, Section G2439.4, and 2006
International Fuel Gas Code, Section 614.5.
Where gas clothes dryers are located in the same space as gas
furnaces and water heaters the Btu input of the gas clothes dryer should
be added to the Btu input of natural draft gas-fired furnaces and natural
draft gas-fired water heaters when sizing the duct supplying outside
combustion air using TABLE 1 (above).
Clothes Dryer Make-Up Air
Test Effectiveness of Combustion Air Supply
The effectiveness of the method of supplying combustion air should be
determined by the procedure contained in Appendix D of the 2009
International Fuel Gas Code. Chimney draft is checked with all exhaust
appliances such as dryers, kitchen fans and bathroom fans operating
and also with the air handling unit fan(s) operating and interior doors
closed.
Reference – 2009 International Fuel Gas
Code; Appendix D: Recommended Procedure
for Safety Inspection of an Existing Appliance
Installation.
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1. COMBUSTION SAFETY
Guide to Attic Air Sealing
If the House has Oil-fired Appliances . . .
Oil-fired furnaces, boilers and water heaters that have natural draft
chimneys require combustion air. It should be supplied from the outside
by a duct. If these ducts are not sized correctly or if they are blocked
this can result in incomplete combustion of the fuel and can lead to
backdrafting. Backdrafting occurs when hazardous exhaust gasses
enter into the house rather than exit through the flue. The requirements
for gas appliances are slightly different than those for oil appliances.
Houses with appliances with natural draft chimneys, even if combustion
air is supplied directly from the outside, should be tested for
backdrafting.
Combustion safety – for more information,
see: www.cpsc.gov/cpscpub/pubs/452.html
and www.epa.gov/iaq/homes/hipcombustion.html
Additionally, if the house has combustion appliances, carbon monoxide
detectors complying with UL 2034 are required in close proximity to the
combustion appliances and outside each separate sleeping area in the
immediate vicinity of the bedrooms.
Reference – 2009 International Residential
Code For One- and Two-Family Dwellings:
Chapter 3 - Building Planning; Section R315
Carbon Monoxide Alarms.
Reference – 2009 International Fuel Gas
Code; Appendix D: Recommended Procedure
for Safety Inspection of an Existing Appliance
Installation.
Provide Combustion Air for Oil Appliances
A duct supplying outside combustion air is required for all natural draft
oil-fired furnaces and natural draft oil-fired water heaters. The size of
this duct is determined by the sum of the Btu input into both appliances
and TABLE 2 (below). In addition, for oil burning appliances, two
additional openings to the inside are required if the oil burning
appliances are enclosed in a room. The size of these two openings can
also be found in TABLE 2. If the oil burning appliances are not
contained in a separate room then these two openings to the interior are
not required. For example, if an oil-fired furnace and oil-fired water
heater are located in an open basement then no additional openings to
the interior are required.
Note – Homes may have more than one
combustion air zone. In other words,
combustion appliances may be located in
more than one part of a house - in different
areas. Each zone needs to be treated
separately.
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1. COMBUSTION SAFETY
Guide to Attic Air Sealing
TABLE 2: Oil-fired Appliances – SINGLE OPENING TO OUTSIDE AND TWO
OPENINGS TO THE INSIDE
Total input rating of
all Appliances in
space (Btu)
from
to
One Exterior Opening
Two Interior
Openings
Free Area
(sq in)
Duct
Diameter (in)
Free Area of Each
Opening (sq in)
40
0
39,999
7
3
40,000
64,999
13
4
65
65,000
99,999
20
5
100
100,000
144,999
28
6
145
145,000
194,999
38
7
195
195,000
254,999
50
8
255
255,000
319,999
64
9
320
320,000
394,999
79
10
395
Reference – Oil Appliances: NFPA 31,
Standard for the Installation of Oil-Burning
Equipment, 2006 Edition; Chapter 5 Air for
Combustion and Ventilation.
Single opening to outdoors, appliances in
unconfined spaces: 5.3 Appliances Located in
Unconfined Spaces; Paragraph 5.3.2.
Single opening to outdoor, appliances in
confined spaces: 5.4.3 Ventilation Air Taken
from Inside the Building - Combustion Air
Taken from Outdoors.
Openings to indoors sized by: 5.4.1 All Air
Taken from Inside the Building; Paragraphs
5.4.1.1 and 5.4.1.2.
Note: Combustion air openings must be
located away from combustion air exhaust
vents if there is a power vented appliance
along with a standard draft hood appliance.
NOTES: The net free areas must take into account louvers and grilles if they are
installed. Assume 75% free area for metal and 25% for wood if the
specific louver/grille dimensions are unknown
Exterior Wall
Combustion Air Supply
Attic Ceiling
Combustion Air Supply
Basement Wall
Combustion Air Supply
Test Effectiveness of Combustion Air Supply
The effectiveness of the method of supplying combustion air should be
determined by the procedure contained in Appendix D of the 2009
International Fuel Gas Code. Chimney draft is checked with all exhaust
appliances such as dryers, kitchen fans and bathroom fans operating
and also with the air handling unit fan(s) operating and interior doors
closed.
Reference – Appendix D – Recommended
Procedure for Safety Inspection of an Existing
Appliance Installation; 2009 International Fuel
Gas Code.
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9
2. VENTILATION FOR INDOOR AIR QUALITY
Guide to Attic Air Sealing
Indoor Air Quality – Controlled ventilation
All houses require small amounts of controlled mechanical ventilation. This
can be accomplished with an exhaust system, a supply system or a
balanced system.
For ventilation systems to ventilate they must be run. Continuous operation
of a ventilation system typically controls indoor contaminants more
effectively than infrequent operation. Proper sizing is important (see
sidebar definition and example). Under sizing and infrequent operation can
lead to elevated levels of indoor contaminants. Over sizing can lead to
excessive energy consumption and elevated levels of interior moisture in
humid climates. Over sized ventilation systems that run continuously
should be avoided.
Reference – ASHRAE Standard 62.2 – 2010:
Ventilation and Acceptable Indoor Air Quality in
Low Rise Residential Buildings
Note: Excessive ventilation is humid climates is
not recommended as it can lead to elevated
interior levels of moisture.
A properly-sized bathroom fan that is vented to the exterior that is controlled
by a timer or operated continuously is one of the acceptable options for an
acceptable exhaust system.
Definition – Mechanical ventilation flow rates
(exhaust or supply) are determined as follows:
Flow Rate = Occupant Rate + Building Rate
Occupant Rate = (no. of bedrooms + 1) x 7.5 cfm
Building Rate = Occupied Floor Area x 0.01 cfm
Example: A three-bedroom house with a floor area
2
of 2,000 ft requires a mechanical ventilation flow
rate of 50 cfm
Occupant Rate = (3 + 1) x 7.5 = 30 cfm
Building Rate = 2,000 x 0.01 = 20 cfm
Flow Rate = 30 + 20 = 50 cfm
Exhaust System
An acceptable supply system is a properly-sized outside air duct connected
to the furnace or air conditioner. The outside air duct requires a volume
damper and a motorized damper and controller to prevent over-ventilation
and under-ventilation.
Definition – Volume Damper: A volume damper
or a balancing damper is a device that adjusts flow
rate – a flap or iris that can be closed off to reduce
flow – or opened up to increase flow. These types
of dampers are usually set once manually.
Definition – Motorized Damper: A motorized
damper is a device that opens and closes via an
electronic control such as a timer or thermostat or
ventilation stat or humidistat. The damper should
also be tied to compressor operation.
Supply System
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2. VENTILATION FOR INDOOR AIR QUALITY
Guide to Attic Air Sealing
An acceptable balanced system is a properly-sized air-to-air heat
exchanger/heat recovery ventilator or an energy recovery ventilator that
both exhausts inside air to the exterior and supplies outside air to the
interior at approximately the same rate. Such systems are typically
designed to operate on a timer or continuously.
Note: Air-to-air heat exchangers or heat
recovery ventilators (HRV’s) are recommended
for cold climates and dry climates.
Energy recovery ventilators (ERV’s) are
recommended for humid climates.
Balanced System
Another acceptable exhaust system is a properly-sized multipoint exhaust
system that is vented to the exterior. Such systems are typically designed
to operate on a timer or continuously.
Note: A typical configuration for a multipoint
exhaust system involves exhausting from
bathroom and wet areas.
Multipoint Exhaust System
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11
3. ATTIC VENTILATION FOR DURABILITY
Guide to Attic Air Sealing
Attic Ventilation with Soffit Vents
Attic ventilation is an important factor in controlling moisture in roof
sheathing and structural members in most types of housing. It therefore
significantly impacts the durability of the typical house. All roofs must be
vented according to the applicable building code. If the roof is not vented
according to the applicable building code then a qualified contractor in the
State should be engaged to install the necessary venting.
For attic ventilation to be effective outside air should enter the attic low at
the attic perimeter and exit high near the attic ridge – intake air inlets down
low – exhaust air outlets up high.
It is important to provide an air gap at the soffit/eave area to control the
accumulation of moisture at the roof sheathing over the soffit/eave area.
This air gap can be used with soffit vents to provide the inlet for attic intake
ventilation air. Continuous soffit vents work best and are recommended.
Definition – Attic Ventilation: The intentional
flow of outdoor air into an attic space balanced
by the intentional flow of attic air to the outside
by natural means.
Note: House attics can be designed and
constructed and renovated to be unvented.
However, this requires specialized knowledge.
Qualified individuals should be consulted when
implementing this type of approach – and the
respective sections of the applicable building
code governing the construction of unvented
attics be followed.
Various types of outlets (ridge vents, mushroom cap vents and upper gable
end vents) can be matched with soffit inlets (see illustration below).
Ridge Vent
Mushroom Cap Vent
Gable Vent
The size of the vents should be determined by the applicable building code.
Most codes require that roofs be vented where the net free ventilating area
be not less than 1/300 of the area of the space to be ventilated – ideally
with the vent area of the low inlet vents being equal to the vent area of the
high outlet vents – in other words the vent area split equally high and low.
Reference – Attic Ventilation: 2009 International
Residential Code for One- and Two-Family
Dwellings; Chapter 8, Roof-Ceiling Construction;
Section R806 Roof Ventilation; R806.2 Minimum
area and R806.3 Vent and insulation clearance.
Soffit vents must be used in conjunction with ridge vents or mushroom cap
vents or gable vents.
Note: If it is not possible to split the vent area
equally between high and low – the low vents
are more important. It is better to have a greater
area of vents down low than vents located up
high. Excessive vents up high can lead to
suction in the attic resulting in the drawing of air
out of the top of the house. Make-up air for attic
ventilation should come from the outside not
from the house.
Continuous Soffit Attic Ventilation –
Insulation Baffles Required in Every Bay
Note: Where radiant barriers are installed below
a roof deck it is necessary to vent the attic space
both above and below the radiant barrier (except
where the radiant barrier is directly attached to
the roof deck). In addition the radiant barrier
must have openings at vent openings such as
ridge vents or off-ridge vents. Radiant barriers
need an adjacent airspace to function – 1” is the
recommended minimum.
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3. ATTIC VENTILATION FOR DURABILITY
Guide to Attic Air Sealing
Attic Ventilation without Soffit Vents
Not all roofs can be vented with soffit vents providing the necessary inlet for
attic intake ventilation air. Some roofs have minimal or non-existent
overhangs or sufficient soffit area for soffit vent installation.
If soffit venting is not possible then an alternative method of providing intake
air inlets low near the roof perimeter should be provided. Two recommended
methods are low gable vents located near the attic ceiling (but above the top
of the level of the attic ceiling insulation) and “eye-brow” vents that can be
located on the top of the sloping roof surface near the soffit area/eave.
Even without soffit ventilation it is important to provide an air gap at the
soffits/eave area to control the accumulation of moisture at the roof sheathing
over the soffit/eave area.
Reference – Attic Ventilation: 2009
International Residential Code for One- and
Two-Family Dwellings; Chapter 8, RoofCeiling Construction; Section R806 Roof
Ventilation; R806.2 Minimum area and R806.3
Vent and insulation clearance.
Note: For attic ventilation to be effective
outside air should enter the attic low at the
attic perimeter and exit high near the attic
ridge – intake air inlets down low – exhaust air
outlets up high.
Various types of outlets (ridge vents, mushroom cap vents and upper gable
end vents) can be matched with low gable vents and “eye-brow” inlets (see
illustrations below).
Homes without accommodation for ventilation openings at the soffit or eave,
shall have a net free ventilating area of not less than 1/150 of the area of the
ventilated attic/roof space.
Ridge Vent
Mushroom Cap Vent
Gable Vent
Hip Roof with Eyebrow Vents
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3. ATTIC VENTILATION FOR DURABILITY
The size of the vents should be determined by the applicable building code.
Most codes require that roofs be vented where the net free ventilating area be
not less than 1/300 of the area of the space to be ventilated – ideally with the
vent area of the low inlet vents being equal to the vent area of the high outlet
vents – in other words the vent area split equally high and low.
Guide to Attic Air Sealing
Note: If it is not possible to split the vent area
equally between high and low – the low vents
are more important. It is better to have a
greater area of vents down low than vents
located up high. Excessive vents up high can
lead to suction in the attic resulting in the
drawing of air out of the top of the house.
Make-up air for attic ventilation should come
from the outside not from the house.
Vent Baffle Supported by Fiber Glass Roll – Even
When There Are No Soffit Vents
The air gap provided by the vent baffle provides redistribution of moisture to
the main body of the attic - even when there are no soffit vents. The vent
baffle should be of plastic or of foam construction – cardboard vent baffles
should be avoided where baffles are needed in unvented soffit/eave
assemblies.
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14
4. AIR SEAL THE ATTIC
Guide to Attic Air Sealing
List of Attic Air Sealing Details
ATTIC ACCESS

Attic Hatch, Access Panel

Pull Down Stair Opening
Note: There are some important openings that
should not be sealed. Combustion air ducts
and soffit, ridge and gable vents are all
intentional openings that must be kept open to
air movement in order to work properly.
FRAMING

Balloon-framed Gable Wall

Gable Truss

Common Wall

Dropped Soffits (bulkheads, arches, cabinet bonnets)

Exterior Top Plate at Soffit

Kneewalls

Two Story Wall
MECHANICAL AND ELECTRICAL PENETRATIONS

Bath Fan

Chimney Chase – Masonry

Chimney Chase – Metal Pipe

Duct Boot

Electrical Box

Plumbing Stack

Recessed Can Ceiling Light

Rigid or Flex Duct and Chase

Top Plate Joints and Penetrations (Electrical/Plumbing)
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15
APPENDIX A – SAMPLE WORK PLAN AND CHECKLIST
Guide to Attic Air Sealing
Sample Work Plan
Inspection of the House
Before developing the work plan, complete an exterior walk-around, an
interior walk-though, and an attic investigation. If any of the following items
are found during the inspection they must be dealt with before proceeding
with the retrofit.
 The house attic has active knob and tube wiring
 The house attic has vermiculite insulation
 The house has natural draft appliances
 The house attic has bathroom fans vented into the attic
 The house has a leaking roof
1. Exterior: As you complete the walk-around, note specifics such as size
and location of the following items:






Soffit Vents
Gable End Vents
Mushroom Vent Caps
Plumbing Stacks
Combustion Air Intakes and Exhausts
Exhaust Air Vents
2. Interior: As you complete the walk-through, note specifics such as size
and location of the following items:








Attic Access and Type
Dropped Soffits
Exterior Wall Perimeter Length, Kneewalls
Two Story walls
Bath Fans in the ceiling
Air Supply Vents through the ceiling
Lighting fixtures in the ceiling, both recessed cans and standard lights
Masonry and Metal Chimney pipe chases
Look for signs of a leaking roof. If the roof is leaking, it must be repaired
before proceeding with the retrofit.
3. Attic: As you complete the attic investigation, note specifics such as size
and location of the following items:










Attic Access Type and Size
Attic Vent Baffles and Exterior Top Plate
Dropped Soffits open to the attic
Kneewalls
Top Plate Joints
Two Story walls
Mechanical, Electrical and Plumbing Penetrations
Bath Fans and Venting
Masonry and Metal Chimney pipe chases
Ductwork
Look for signs of a leaking roof, active knob and tube wiring, vermiculite
insulation or bathroom fans ducted into the attic or kneewall. If any one of
these are found, they must be repaired before proceeding with the retrofit.
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16
APPENDIX A – SAMPLE WORK PLAN AND CHECKLIST
Guide to Attic Air Sealing
Checklist and Work Plan
Stop-Work Items
The house attic has active knob and tube wiring.
YES - The house must be rewired prior to the attic being air sealed and insulated.
NO - Proceed
The house attic has vermiculite insulation.
The vermiculite insulation may contain asbestos and must be removed prior to the attic being air sealed and insulated. Professional advice should be obtained. Contact your State
YES Department of Health.
NO - Proceed
The house attic has bathroom fans vented into the attic.
YES - Bathroom fans must be vented to the outside prior to the attic being air sealed and insulated.
NO - Proceed
The house has a leaking roof.
YES - The leaking roof must be fixed prior to the attic being air sealed and insulated.
NO - Proceed
INTERIOR WALK THROUGH
1 - Locate the mechanical space within the home. Find the information tags on each of the appropriate appliances. Record the following information:
Gas Furnace with Natural Draft Exhaust
Oil Furnace with Natural Draft Exhaust
A = Btu Input
E=
Btu Input
Gas Water Heater with Natural Draft Exhaust
Oil Water Heater with Natural Draft Exhaust
B = Btu Input
F=
Btu Input
Gas Boiler with Natural Draft Exhaust
Oil Boiler with Natural Draft Exhaust
C = Btu Input
G=
Btu Input
Gas Fired Dryer
D = Btu Input
2 - Totalize all Natural Draft Appliance Input
Total Btu of All Gas Fired appliances in mechanical space Y = A+B+C+D
Total Btu of All Oil Fired appliances in mechanical space X = E+F+G
Total Btu of All Gas Fired appliances in mechanical space Z = X+ Y
3 - Check for Outdoor Combustion Air Supply Vent
If Combustion Air Supply Vent is Present
Diameter of Pipe
Number of Pipe (s) present
Pipe Material
Interior Location of Pipe
Outside location of Pipe and Height off of Ground
Compare Diameter and Total Btu present with Table 1 or Table 2 if Area on-site is equal to or greater than the area required
*Always compare with Table 2 if any oil fired natural draft appliances are present
If Outdoor Combustion Air Supply Vent is Not Present or Undersized
A properly sized combustion Air Supply Vent must be Installed
Determine appropriate combustion air supply vent required from Table 1 and/or Table 2
Determine installation route for vent and approximate length required
4 - Check for Additional Indoor Air Vents if Oil Fired Natural Draft Appliances are Present and located in an Enclosed Space
If Indoor Air Vents are Present
Area of vents = A
A=
Grill material - Wood (K = 0.25) or Metal (K = 0.75)
Effective Vent Area - EA = A x K
Example - for a metal 100sqin vent - EA = 100 x 0.75 = 75 sqin
EA=
Compare this EA with the required effective area in Table 2.
If the area present does not meet the requirements of Table 2, additional venting area must be installed.
If Indoor Air Vents are Not Present or Undersized
Determine appropriate vent area required from Table 2
Determine installation location for vent(s)
5 - Check for Controlled Ventilation
Supply system - a properly sized outside air duct connected to the furnace or air conditioner
If a Supply system does not exist check for an exhaust system
Diameter of Pipe
Number of Pipe (s) present
Pipe Material
Location of Pipe
Outside location of Pipe and Height off of Ground
Damper Present and Functioning
YES
NO
Exhaust System
If an exhaust system or a supply system do not exist, one of either must be installed.
Number of Bathroom fans present
Bathroom fans exhaust to outdoors (Must be re-vented if vented into attics, kneewalls, conditioned crawlspaces, garages etc.)
Fans exhaust to unobstructed location
YES
NO
6 - Carbon Monoxide Detectors
Check for Operational Carbon monoxide detectors (test with test button)
YES
NO
Check Location of Carbon Monoxide Detectors and ensure they are in close proximity to Natural Draft Appliances.
If Carbon Monoxide Detectors do not exist, are improperly located, or do not function properly a Carbon monoxide detector must be installed
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APPENDIX A – SAMPLE WORK PLAN AND CHECKLIST
Guide to Attic Air Sealing
CEILING AND ATTIC INVESTIGATION
1 - Attic Hatch
Approximate perimeter of opening
Approximate area of opening
3 - Attic Vent Baffles and Exterior Top Plate
Approximate linear feet
5 - Kneewalls
Approximate number of joist bays
Approximate knee wall area
7 - Two Story Wall
Approximate number of joist bays or linear feet of interior wall
Approximate wall area
9 - Bath Fan
Quantity, Make(s) and Model(s)
11 - Masonry Chimney Chase
Quantity
Gap width to be covered
13 - Electrical Box
Quantity
15 - Recessed Can Ceiling Light
Quantity
Diameter
Height above Ceiling Drywall
17 - Balloon Framed Gable
Approximate number of joist bays or linear feet of common wall
2 - Pull Down Stair Opening
Approximate perimeter of opening
Approximate area of opening
4 - Dropped Soffits (bulkheads, arches)
Linear Feet
Depth/Width
6 - Top Plate Joints
Approximate number of joist bays or linear feet of interior wall
8 - Mechanical/Electrical Penetrations
Approximate number of penetrations
10 - Metal Chimney Pipe Chase
Quantity
Gap width to be covered
12 - Duct Boot
Quantity
Average Size
14 - Plumbing Stack
Quantity
Diameter
16 - Common Wall
Approximate number of joist bays or linear feet of common wall
18 - Supply or Return Ducts
Quantity
Diameter
EXTERIOR WALK AROUND
Attic ventilation
If soffits vents and one of Gable end vents, ridge vents or mushroom caps are not present, attic ventilation must be installed prior to air sealing and insulating.
1 - Lower Vent Area - Soffit Vents
Length (paced on ground or measured for all sides) = L
Width (approximated from brick widths, overhang estimate or measured) = W
Total Soffit Area TSA = L x W
2 - Higher Vent Area
Gable End Vents - Rectangular or Square
Length (Estimated or measured) = L
L=
Width (Estimated or measured) = W
W=
Total Rectangular Area TRA = L x W
TRA=
Mushroom Vent Caps
Quantity Present
QTY=
TMA = Total Present x Free Area Per Cap
TMA=
L=
W=
TSA=
Gable End Vents - Triangular
Length (Estimated or measured) = L
Height (Estimated or measured) = H
Total Triangular Area TTA = ½ L x H
Ridge Vent
Length (Estimated or measured) = L
Height (Estimated or measured) = H
Total Ridge Vent Area TRVA = L x H
L=
W=
TTA=
L=
W=
TRVA=
Total Higher Vent Area = TRA + TTA + TMA + TRVA
THVA=
3 - Total Higher Vent Area should equal or exceed the amount of Total Lower Vent Area provided at the soffit (TSA)
The sum of these areas should be at least equal to the 1/300 (or 1/150) rules discussed in detail in the Attic Air Sealing Guide - Appendix B.
Ideally the vent area should be split between high and low.
4 - Take note of the following. Measure where appropriate
Location and size of plumbing stacks
Location and size of possible combustion air supply vents
Location of possible exhaust air vents
Checklist Verification
Upon completion of this checklist verify that you have made provisions for:
Combustion air for Combustion Safety
If you have gas or oil fired furnaces or gas or oil fired water heaters that have natural draft chimneys combustion air supplied directly from the outside is required. Install carbon
monoxide detectors.
Air Supply Present and Adequately Sized
Air Supply System Must be Installed
Controlled ventilation for Indoor Air Quality
As a minimum houses require an exhaust fan or an outside air supply duct connected to the furnace or air conditioner.
Controlled Ventilation Present
Controlled Ventilation Must be Installed
Attic Ventilation for Durability
All roofs must have soffit vents and be vented according to the applicable building code.
Attic Venting Present and Adequately Sized
Attic Venting System Must be Installed
Air Sealing all penetrations to the attic space and additional insulation for energy efficiency.
Air sealing is to be completed as per the specifications in this document. Insulating is to be completed as per the manufacturers recommendations.
All penetrations reviewed, measured and quantified
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APPENDIX A – SAMPLE WORK PLAN AND CHECKLIST
Guide to Attic Air Sealing
Customer Communication
Upon Completion of the Inspection and the Checklist, provide a statement
of work to the Homeowner.
Report the findings of your inspection and describe the work required. Be
sure to include any stop work items.
Example: For this home we will require additional venting to the mechanical room,
a new bathroom fan that will supply the required ventilation, air sealing of the attic
including all penetrations present, and additional insulation placed once the air
sealing is complete.
If you are a qualified professional or have sub-contracted qualified
professionals who are able to repair the stop-work items and to complete
the job in full, inform the Homeowner that you will provide them with a quote
to complete the work within a reasonable time period. If you do not have
the capability to repair the stop-work items, inform the Homeowner that they
will have to hire additional qualified professionals to complete the necessary
tasks before you are able to complete your portion of the work.
Provide the Homeowner with a quote for the work that is to the best of your
knowledge complete and contains all items that will require installation,
repair or replacement. Be aware that while you are quoting the job that the
Homeowner may have already had, or may plan to have another contractor
also bidding on the job. If the Homeowner is presented with a much more
thorough review of the home or an equal review of the home with a better
quote, you may not be awarded the job. A complete and thorough review of
the home with an accurate quote can help win the job. Provide this Guide
and the completed checklist to the Homeowner.
Schedule the time required to complete with the Homeowner. The
Homeowner may want to be present during the construction or have
someone present to oversee the construction. Inform the Homeowner that
the person present overseeing your work must be at least 18 years of age.
On completion of the work, remind the Homeowner that any future work on
the house involving a combustion appliance or powerful exhaust fan (e.g.,
kitchen exhaust greater than 300 cfm) must be provided with adequate
combustion air or make-up air according to the building code.
IMPORTANT
The Federal Trade Commission’s R-value Rule (16 CFR Part 460) specifies
substantiation and disclosure requirements for thermal insulation products
used in the residential market, and prohibits certain claims unless they are
true. The primary disclosure required is the insulation product’s “R-value.”
R-value is the numerical measure of the ability of an insulation product to
restrict the flow of heat and, therefore, to reduce energy costs—the higher
the R-value, the better the product’s insulating ability. To assist consumers,
the Rule requires sellers (including insulation manufacturers, professional
installers, new home sellers, and retailers) to disclose the insulation
product’s R-value and related information, before retail sale, based on
uniform, industry-adopted standards. This information enables consumers
to evaluate how well a particular insulation product is likely to perform, to
determine whether the cost of the insulation is justified, and to make
meaningful, cost-benefit based purchasing decisions among competing
products.
For more information, please see
www.ftc.gov/energy.
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19
APPENDIX B – SAMPLE CALCULATIONS
Guide to Attic Air Sealing
Attic Ventilation
The total net free ventilating area should not be less than 1/300 of the area
of the attic/roof space to be ventilated and ventilation openings should be
located both high and low in the roof assembly. Lower ventilation openings
should be provided in each rafter bay of the roof assembly. A minimum 1inch space should be maintained between the insulation and the roof
sheathing and between the insulation and any roof vent openings.
The area of the attic/roof space to be ventilated is the area of the floor or
ceiling that separates the attic/roof space from conditioned space.
Therefore, minimum total net free ventilation area for an attic/roof space is
equal to the area of the floor or ceiling beneath the roof assembly divided by
300.
It is recommended that not more than 50 percent of the net free ventilating
area be located high on the roof. These upper ventilation openings should
be located at least 3 feet above the soffit or eave vent openings.
Definition: Net free ventilating area refers to
the clear open area of a vent taking into account
the restrictions of the vent screens and vent
slots. For example most screened vents have a
60 percent free area.
Note: The area of the attic/roof space is the
sloped ceiling area in situations such as where
the ceilings are applied directly to the underside
of the roof rafters and where the attic/roof space
is within scissor trusses.
Homes without roof overhangs or other accommodation for ventilation
openings at the soffit or eave, should have a net free ventilating area of not
less than 1/150 of the area of the ventilated attic/roof space. Refer to the
example for 1:150 attic ventilation below.
Example for 1:300 high/low attic ventilation
Consider a house that is 30 ft wide by 42 ft long. The top floor ceiling is flat
in this example so the area of the attic space is equal to the area of the foot
print of the house.
The area of the ventilated attic space is therefore:
30 ft x 42 ft = 1260 ft2
The required total net free ventilation area is:
1260 ft2/ 300 = 4.2 ft2
Converting ft2 to in2, the required total net free ventilation area yields:
4.2 ft2 x 144 in2/ft2 = 605 in2(note that the required area is
rounded up to the nearest inch)
Approximately 50% of the total net free ventilating area should be located in
the upper portion of the roof - at least 3 ft above the soffit or eave vents.
The required net free ventilating area of the upper roof vents should be:
0.5 x 605 in2 = 303 in2
The remainder of the required free ventilating area should be provided by
soffit or eave vents so that the total required free ventilating area is
achieved. It is important that the soffit or eave vents provide ventilation in
each rafter bay.
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20
APPENDIX B – SAMPLE CALCULATIONS
Guide to Attic Air Sealing
Example for 1:150 attic ventilation
Considering the same 30 ft by 42 ft house only this time without soffit vents,
eyebrow vents or low gable vents. If it is not possible to provide ventilation
openings at the bottom of the roof assembly, then the required minimum
free ventilating area is 1/150 of the area of the attic/roof space to be
ventilated.
The area of the ventilated attic space is:
2
30 ft x 42 ft = 1260 ft
The required total net free ventilation area is:
2
1260 ft / 150 = 8.4 ft
2
2
2
Converting ft to in , the required total net free ventilation area yields:
8.4 ft2 x 144 in2/ft2 = 1210 in2 (note that the required area is
rounded up to the nearest inch)
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21
APPENDIX C – MATERIAL SPECIFICATION
Guide to Attic Air Sealing
Air Barrier (ABM) Any rigid or semi rigid material that does not allow air to
pass through it. Examples: gypsum board, plywood/OSB, foam board, duct
board (with a facing flame spread rating of 25 or less), sheet metal or
dimensional lumber.
Relevant Test Methods: ASTM E2178 and E283
Fire Rated Sealant (FRS) Any sealant that is UL listed for use in any
details requiring an approved fire rated sealant. Example: Sealing sheet
metal ABM to a chimney.
Relevant Test Method: ASTM 814
Required Certification: UL1479
Insulation Any material which significantly slows down or retards the flow
or transfer of heat. Building insulation types are classified according to form
(e.g., loose-fill, batt, flexible, rigid, reflective, and foamed-in-place) or
material (fiber glass, rock and slag wool, organic fiber, foam plastic)
Relevant Test Methods: ASTM C177, ASTM C518, ASTM C976, CFR
Title 16, Part 460
Rigid Foam Rigid board material that provides thermal resistance. Foam
plastic such as EPS, XPS, and polyisocyanurate.
Relevant Test Methods: ASTM C177, ASTM C518, ASTM C976, ICC-ES
AC12, CFR Title 16, Part 460
Sealant Any flexible product which when applied to the join of two or more
materials will adhere and permanently seal the joint to the passage of air.
Examples: caulk, foam, and mastic.
Relevant Test Method: Foam sealants - ASTM C1642
Relevant Test Method: Acrylic, silicone, and urethane caulk - ASTM C-920
Required Certification: Water based duct sealant - UL 181A-M, UL 181B-M
Spray Foam Relevant Test Methods: "ICC-ES AC377, ASTM E84 CFR
Title 16, Part 460"
Tape (for ducts) Required Certification: UL-181
Tape (for air sealing) Relevant Test Methods: ASTM D3330, ASTM D882
Weatherstripping Relevant Test Methods: ASTM C509
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22
ATTIC HATCH
Guide to Attic Air Sealing
TASK – Control air leakage at the attic access hatch.
Steps
• Lift off and set aside attic access cover. [1]
• Cut and adhere two layers of rigid foam to access
cover.
• Cut two cross pieces of framing lumber of equal
height of ceiling joists to form a box around the
access hole. [2]
• Mechanically Fasten wood cross pieces to joists.
1.
• Apply an adhesive backed weather-stripping to the
molding or ledge on which the cover will rest. [3]
• Cut and Fasten insulation Blocking material which
will be at least 4 inches above the finished
insulation level.
Detail ready for insulation [4]
2.
3.
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
4.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
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PULL DOWN STAIR OPENING
Guide to Attic Air Sealing
TASK – Control air leakage at the attic pull down stair opening.
Steps
• Expose all framing around pull down stair opening.
[1]
• Construct box opening to enclose pull down stairs.
Top of box should extend 6 inches above top of
finished insulation level.
• Fasten box opening to framing with Fasteners.
1.
• Install a continuous bead of Sealant at the inside
corners of the box opening and at the inside
perimeter base of the box opening to the framing.
• Apply an adhesive backed weather-stripping to the
ledge on which the cover will rest. [2]
• Construct a covering to the box opening.
• Cut and adhere two layers of rigid foam to the box
opening cover. [3]
Detail ready for insulation [4]
2.
3.
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
4.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
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BALLOON-FRAMED GABLE WALL
Guide to Attic Air Sealing
TASK – Control air leakage where the gable wall meets the ceiling.
Steps
• Fully expose framing and ribbon board. [1]
• Seal all sides of wood blocking and back side of
ribbon board with Sealant.
• Seal gypsum board/top plate join with Sealant.
• Seal ribbon board/gypsum board join with Sealant
• Install insulation baffle. [2]
1.
• Install fiber glass batt insulation roll (or other
suitable material) as support for baffle. [3]
Detail ready for insulation [4]
2.
3.
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
4.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
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BALLOON-FRAMED GABLE WALL – ALTERNATE
Guide to Attic Air Sealing
TASK – Control air leakage where the gable wall meets the ceiling.
Steps
• Fully expose framing and ribbon board. [1]
• Install insulation baffle. [2]
• Roll up a fiber glass batt and friction fit it to fill the
wall cavity to provide a backing for spray foam. [3]
• Use a foam pack, spray foam the perimeter top
plate to the baffle completely covering the top
plate extending 3 inches over the gypsum board.
[4]
1.
• Use a foam pack, spray foam full gable wall cavity
completely covering the fiber glass roll and ribbon
board extending 3 inches over the gypsum board.
[4]
Detail ready for insulation [5]
2.
3.
Terminology
4.
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
5.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
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GABLE TRUSS
Guide to Attic Air Sealing
TASK – Control air leakage where the gable wall meets the ceiling.
Steps
• Fully expose framing and bottom chord of gable
truss. [1]
• Install insulation baffle. [2]
• Use a foam pack, spray foam perimeter top plate
to the baffle completely covering the top plate
extending 3 inches over the gypsum board. [3]
1.
• Use a foam pack, spray foam bottom of gable
truss and perimeter top plate extending 3 inches
over the gypsum board. [3]
Detail ready for insulation [4]
2.
3.
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
4.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
COMMON WALL
Guide to Attic Air Sealing
TASK – Control air leakage at the common wall.
Steps
• Fully expose framing and edge of ceiling gypsum
board. [1]
• Use a foam pack, spray foam over the mineral
firestop completely covering it, the bottom framing
members extending three inches over the gypsum
board. [2]
1.
Detail ready for insulation [3]
2.
3.
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
DROPPED SOFFITS (Bulkheads, Arches)
Guide to Attic Air Sealing
TASK – Control air leakage between the conditioned space below and the unconditioned attic space above at
dropped soffits.
Steps
• Expose the dropped soffit including the framing
[1].
• Measure and pre cut the ABM to be used to cover
the drop or opening in the ceiling.
• Fix in place the ABM using adhesive or Fasteners.
• Air seal all edges of ABM to framing using Sealant
[2].
1.
Detail ready for insulation [3,4]
2.
3.
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
4.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
EXTERIOR TOP PLATE AT SOFFIT
Guide to Attic Air Sealing
TASK – Control air leakage at top plate, provide insulation coverage of top plate, direct attic ventilation air.
Steps
• Fully expose the top plate and fold or cut the
Baffle to make a vertical backstop. [see below]
• Fix Baffle in place leaving the top plate fully
exposed for maximum insulation. [1]
• Seal the gypsum board/top plate join with Sealant.
[2]
1.
Alternate Method
• Fully expose the top plate and fold or cut the
Baffle to make a vertical backstop. [see below]
• Fix Baffle in place leaving the top plate fully
exposed for maximum insulation. [1]
• Using a foam pack, spray foam to backstop
extending over gypsum board/top plate joint. Do
not seal ventilation space behind insulation baffle.
Detail ready for insulation [3]
2.
Note: Tape cut line
after fold if loose fill
insulation is used
3.
Alternate Method
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
2a.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
EXTERIOR TOP PLATE AT SOFFIT – ALTERNATE
Guide to Attic Air Sealing
TASK – Control air leakage at top plate, provide insulation coverage of top plate, direct attic ventilation air.
Alternate Method
• Fully expose the top plate and fold or cut the
Baffle to make a vertical backstop.
• Fix Baffle in place leaving the top plate fully
exposed for maximum insulation [1].
• Seal the gypsum board/top plate join with Sealant.
[2]
1.
• Install fiber glass batt insulation roll (or other
suitable material) as support for baffle [3].
Detail ready for insulation [4,5]
2.
3.
Terminology
4.
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
5.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
KNEEWALLS
Guide to Attic Air Sealing
TASK – Control air leakage between the conditioned floor space and unconditioned attic space.
Steps
1.
• Expose approximately an 18-inch attic joist area
under the kneewall. [1]
• Cut and friction fit or Fasten ABM to span the joist
cavity directly under the kneewall lining it up with
the gypsum board of the conditioned room above.
[2]
• Seal all edges of ABM with Sealant taking care to
seal the hard to reach top edge. [3]
• Install insulating sheathing over kneewall framing.
[4]
Detail ready for insulation [4]
2.
3.
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
4.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
KNEEWALLS – Alternate Method with Spray Foam
Guide to Attic Air Sealing
TASK – Control air leakage between the conditioned floor space and unconditioned attic space.
Steps – Alternate Method with Spray Foam
1.
• Expose approximately an 18-inch attic joist area
under the kneewall. [1]
• Roll up a fiber glass batt and friction fit it to fill the
floor joist cavity under the kneewall to provide a
Backing for spray foam. [2]
• Spray foam full cavity height and width against the
Backing. [3]
• Install insulating sheathing over kneewall framing.
[4]
Detail ready for insulation [4]
2.
3.
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
4.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
TWO STORY WALL
Guide to Attic Air Sealing
TASK – Control air leakage through wall cavity into attic space.
Steps
• Expose wall cavity area. [1]
• Pre cut ABM to fit cavity behind band board.
• Align ABM with bottom edge of band board and
Fasten. [2]
• Seal all four edges of installed bottom plate with
Sealant. [3]
1.
• Install insulating sheathing over wall framing and
extend upwards above top band board to act as
insulation dam. [5]
Detail ready for insulation [4,5]
2.
3.
Terminology
4.
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
5.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
TWO STORY WALL – Alternate Method
Guide to Attic Air Sealing
TASK – Control air leakage through wall cavity into attic space.
Steps – ALTERNATE METHOD
• Expose wall cavity area. [1]
• Friction fit Backing (e.g., fiber glass insulation roll)
in cavity to the level of the bottom edge of the
band board. Adjust so that the top of the Backing
is at the bottom edge of the band board. [2]
• Using a foam pack, spray foam onto the Backing
completely filling the bottom of the cavity. [3]
1.
• Replace insulation and install insulating sheathing
over wall framing and extend upwards above top
band board to act as insulation dam. [5]
Detail ready for insulation [4,5]
2.
3.
Terminology
4.
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
5.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
BATHROOM FAN
Guide to Attic Air Sealing
TASK – Control air leakage at the bathroom fan and create an insulation shield.
Steps
1.
• Expose ceiling gypsum board approximately 12
inches both sides of fan. [1]
• Create a 5-sided box with ABM which will
comfortably fit over the fan insuring all corners are
sealed.
• Scribe and cut access in the box for exhaust duct
outlet.
• Seal box to ceiling with Sealant.
• Seal notched ABM to exhaust outlet. [2]
Detail ready for insulation [3,4]
2.
3.
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
4.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
MASONRY CHIMNEY CHASE
Guide to Attic Air Sealing
TASK – Control air leakage at the chimney chase.
Step 1
1.
• Expose all framing area. [1]
• Measure and cut sheet metal ABM into strips to
be Fastened to framing.
• Seal all framing joints around the chase with
Sealant. Lay a generous, continuous bead of
Sealant along the top edge of the chase framing.
• Place sheet metal ABM on framing and in contact
with the masonry. Tack in place with a few
Fasteners.
• Seal the metal to the masonry with FRS. Also seal
the metal joints. [2]
Step 2
• Cut insulation Thermal Blocking material to keep
insulation at least 3 inches from the chimney.
Thermal Blocking should be at least 4 inches
higher than final insulation level.
• Fasten Thermal Blocking to framing. [3]
2.
Detail ready for insulation [4]
3.
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
4.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
METAL CHIMNEY VENT CHASE
Guide to Attic Air Sealing
TASK – Control air leakage at the metal chimney pipe chase and provide Thermal Blocking to separate insulation
from the metal chimney vent pipe.
Step 1 – Seal Chase
1.
• Expose the chase including the framing. [1]
• Precut two pieces of sheet metal ABM to cover
the chase opening allowing for approximately a 1inch overlap in center.
• Scribe and cut two half circles in the ABM so that
it fits around the vent pipe with approximately a 1inch overlap while covering the chase.
• Fasten the two halves of the metal ABM to the
adjacent framing while enclosing the chimney vent
pipe.
• Seal the overlap and joint of the ABM to the metal
chimney vent pipe with FRS.
• Seal all edges of the ABM to framing with Sealant.
[2]
Step 2 – Insulation Thermal Blocking
2.
3.
• Manufacture an insulation shield (Thermal
Blocking) from metal coil stock so that a 3-inch
clearance is provided between the insulation
shield (Thermal Blocking) and the metal chimney
vent pipe. Shield height should be 4 inches taller
than the finished insulation level.
• Fasten
insulation
Thermaling
to
ABM,
maintaining the 3-inch clearance.
• Ensure that there is a top cover of the 3-inch gap
so that insulation does not accidently fall into the
gap. [4]
Detail ready for insulation [5]
Terminology
4.
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
5.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
METAL CHIMNEY VENT CHASE - ALTERNATE
Guide to Attic Air Sealing
TASK – Control air leakage at the metal chimney pipe chase and provide Thermal Blocking to separate insulation
from the metal chimney vent pipe.
Step 1 – Seal Chase – ALTERNATE METHOD
1.
2.
• Expose the chase including framing. [1]
• Cut two cross pieces of framing lumber of equal
height of ceiling joists to form a box around the
pipe.
• Mechanically Fasten wood cross pieces to joists
making sure that the wood is at least 3 inches
from pipe. [2]
• Scribe and cut two half circles in the ABM so that it
fits around the vent pipe with approximately a 1
inch overlap while covering the chase.
• Lay a generous, continuous bead of Sealant on
the top edge of the framed box and all joints of the
box.
• Fasten the two halves of the metal ABM to
accompanying framing while enclosing the pipe.
• Seal the overlap and join of the ABM to the vent
pipe with FRS. [3]
Step 2 – Insulation Thermal Blocking
3.
• Manufacture an insulation shield (Thermal
Blocking) from metal coil stock so that a 3-inch
clearance is provided between the insulation
shield (Thermal Blocking) and the metal chimney
vent pipe. Shield height should be 4 inches taller
than the finished insulation level.
• Fasten insulation Thermal Blocking to ABM,
maintaining the 3-inch clearance.
• Ensure that there is a top cover of the 3-inch gap
so that insulation does not accidently fall into the
gap. [4]
Detail ready for insulation [5]
Terminology
4.
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
5.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
DUCT BOOT
Guide to Attic Air Sealing
TASK – Control air leakage at the duct boot ceiling penetration.
Steps
• Expose duct boot.
• Seal all sides of the duct boot to the gypsum board
with a bead of 2.0 pounds per cubic foot spray
foam. [1,1a]
Detail ready for insulation [2,3]
1.
2.
3.
Alternate Method
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
1a.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
ELECTRICAL BOX
Guide to Attic Air Sealing
TASK – Control air leakage through the electrical box and around the electrical box.
Steps
• Expose box and approximately 12 inches of ceiling
gypsum board.
• Cut two cross pieces of framing lumber of equal
height of ceiling joists to form a box around the
box.
• Mechanically Fasten wood cross pieces to joists
making sure that the wood is at least 3 inches
from box. [1]
1.
• Pre cut ABM to form cover for box with a cut out
for the wire.
• Seal all framing joints of the box and lay a
generous, continuous bead of Sealant along top
edge of box.
• Place ABM onto box frame firmly and tack with a
few Fasteners [2,3].
• Seal wire cutout with Sealant.
Detail ready for insulation [3,4]
2.
3.
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
4.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
ELECTRICAL BOX – Alternative Method
Guide to Attic Air Sealing
TASK – Control air leakage through the electrical box and around the electrical box.
Steps – Alternative Method
• Expose box and approximately 12 inches of ceiling
gypsum board [1].
• Seal the box to the gypsum board, wire entry
points and any box openings with FRS [2].
Detail ready for insulation [3]
1.
2.
3.
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
PLUMBING STACK
Guide to Attic Air Sealing
TASK – Control air leakage at the penetration.
Steps
• Expose all of top plate and plumbing stack. [1]
• Seal the top plate with Sealant and the plumbing
stack with foam. Note that spray foam sealant
used in this application must have an acceptable
rating as a fireblocking material. [2]
Detail ready for insulation [3,4]
1.
2.
3.
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
4.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
RECESSED CEILING LIGHT
Guide to Attic Air Sealing
TASK – Control air leakage through the ceiling light, control air leakage between the ceiling light and gypsum board
ceiling and create an insulation shield (Thermal Block).
Steps
1.
• Expose ceiling gypsum board approximately 12
inches both sides of the recessed can. Add
Sealant at joist to gypsum board joint, extending
past ends of gypsum board box (see below) [1]
• Precut 5/8 piece of drywall 42 inches long by 22
1/2" (for 24” o.c. ceiling joist spacing) or 14 1/2"
(for 16” o.c. spacing). [A]
• Score back side of gypsum board stock at 12
inches from ends. [B] Break along scored lines
and form an inverted “U” shape of ABM to keep
insulation 3” from can. [2]
• Install gypsum board side closure. [3]
• Tape seams of gypsum board box and join to
ceiling with Sealant. [4]
• Replace bulb with compact fluorescent (CLF) bulb
(less than 60 watts) to reduce heat build-up.
2.
3.
Detail ready for insulation [5]
A.
B.
Terminology
4.
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
5.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
RIGID DUCT AND DUCT CHASE
Guide to Attic Air Sealing
TASK – Control air leakage at the duct chase.
Steps
1.
• Expose the chase and the framing area. [1]
• Measure and cut ABM into strips to be Fastened
to framing.
• Seal all framing joints around the chase with
Sealant. Lay a generous continuous bead of
Sealant along the top edge of the chase framing.
[2]
• Place ABM on framing leaving 1/4 inch gap
between rigid duct and ABM. Fasten in place with
Fasteners.
• Seal the ABM to the duct with Sealant. Also seal
the joints in the ABM. [3]
Detail ready for insulation [4]
2.
3.
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
4.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
FLEX DUCT AND DUCT CHASE
Guide to Attic Air Sealing
TASK – Control air leakage at the duct chase.
Steps
1.
• Expose the chase and the framing area. [1]
• Measure and cut ABM to cover entire chase.
• Cut the ABM into two halves and then cut half
circles to encompass the flex duct.
• Seal all framing joints around the chase with
Sealant. Lay a generous continuous bead of
Sealant along the top edge of the chase framing.
[2]
• Place ABM on framing and in contact with the
duct. Fasten in place with Fasteners.
• Seal the ABM to the duct with Sealant. Also seal
the joints in the ABM. [3]
Detail ready for insulation [4]
2.
3.
Terminology
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
4.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
TOP PLATE JOINTS AND PENETRATIONS
Guide to Attic Air Sealing
TASK – Control air leakage between top plates and ceiling gypsum board and control leakage at electrical and
plumbing penetrations.
Steps
• Locate and expose all top plates. [1]
• Air seal all joints of drywall to framing and any
penetrations with appropriate Sealant. [2,3]
Alternate Method using Foam Pack
1.
• Locate and expose all top plates. [1]
• Choose a foam dispenser tip that will create a fan
of approximately 5 inches.
• Spray a continuous layer of foam so as to totally
cover the width of the top plate and adhere to the
gypsum board on both sides of the framing. [4]
Details ready for insulation [5]
2.
3.
Terminology
4.
Air Barrier Material (ABM) --- Any rigid or semi rigid material that
does not allow air to pass through it. Examples: gypsum board,
plywood/OSB, foam board, duct board, sheet metal or dimensional
lumber.
Backing --- Any material that serves as a surface to which foam can
be sprayed so as to provide an air barrier. Examples: rolled up fiber
glass batts.
Baffle (B) --- Manufactured chutes that create an insulation stop and
direct ventilation air flow up and over the insulation; typically rigid
foam board or cardboard.
Thermal Blocking --- Any rigid material that keeps insulation from
heat sources like chimneys or recessed lights. Examples: sheet
metal and gypsum board.
5.
Fasteners --- Staples, screws or nails that are used to permanently
attach Thermal Blocking or ABMs to framing.
Sealant --- Any flexible product which when applied to the join of two
or more materials will adhere and permanently seal the joint to the
passage of air. Examples: caulk, foam, and mastic.
Fire Rated Sealant (FRS) --- Any sealant that is UL listed for use in
any details requiring an approved fire rated sealant. Example:
Sealing sheet metal ABM to a chimney.
www.buildingscience.com
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