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Retrot Techniques and Technologies:
A Guide for Contractors to Share with Homeowners
Preface
The U.S. Department of Energy recognizes the enormous potential
that exists for improving the energy efciency, safety, and comfort
of existing American homes. This series of Retrot Techniques and
Technologies describes approaches for homeowners and builders
working on existing homes. This guide will help homeowners identify
ways to make their homes more comfortable, more energy efcient,
and healthier to live in. It also identies the steps to take, with the
help of a qualied home performance contractor, to seal unwanted
air leaks while ensuring healthy levels of ventilation and avoiding
sources of indoor air pollution. Contractors can use this document to
explain the value of these air sealing measures to their customers. The
references in this document provide further explanation of air sealing
techniques and technologies.
Studies show that the measures described in this guide can typically
achieve whole-house energy savings of 10% to 20% over pre-retrot
energy usage. In older homes or homes with greater levels of air
leaks, savings may be much higher.
These practices are based on the results of research and
demonstration projects conducted by the U.S. Department of
Energy’s Building America and Home Performance with ENERGY
STAR sponsored by the U.S. Environmental Protection Agency
and DOE. Home Performance with ENERGY STAR offers a
comprehensive, whole-house approach to improving the energy
efciency and comfort of existing homes and requires a test-in/
test-out to test combustion products (www.energystar.gov/
homeperformance).
DOE’s Building America has worked with some of the nation’s
leading building scientists and more than 300 production builders on
over 41,000 new homes. Building America’s research applies building
science to the goal of achieving efcient, comfortable, healthy, and
durable homes.
Please submit your comments via e-mail to:
George James (George.James@ee.doe.gov)
You can learn more about Building
America and download additional copies
of this document, other best practices,
research reports, and case studies at
www.buildingamerica.gov
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Contents
Preface ..............................................................i
Introduction ........................................................ 1
Finding a Contractor .............................................. 3
Test In/Test Out ....................................................4
Diagnostic Tools Used During Test-In Test-Out .................. 6
Safety and Health Issues .......................................... 7
Ventilate it Right ...................................................8
New Code Air Sealing Requirements .............................9
An Air Sealing Checklist ..........................................10
Introduction
Imagine opening a window in your house and leaving it that way
24 hours a day, all year long. On balmy spring days, the breeze wouldn’t
be so bad. But, in the freezing cold of winter and the sticky heat of
summer, with the furnace or air conditioner on, smart homeowners
would recognize they might as well be throwing buckets of quarters
out the window to pay for the escaping heated or cooled air.
Air leaks in most existing homes add up to an open window in your
home. Air sealing is one of the least expensive and most cost-effective
measures you can take to improve your home’s comfort and energy
efciency. By sealing uncontrolled air leaks, you can expect to see
savings of 10% to 20% on your heating and cooling bills, and even
more if you have an older or especially leaky
house. But, before you grab your caulk gun,
there are some things you should consider.
Many older homes lack proper ventilation, so
they depend on those cracks and leaks to let in
air, especially when fuel-burning appliances are operating inside the
home. Without ventilation, carbon monoxide and air pollutants from
cleaning chemicals, combustion appliances, and off-gassing household
products can build up, creating an unhealthy and even dangerous
environment in the home. Opening windows is one way to ventilate,
but there are times when opening the windows is not practical (e.g., it
is too cold or too hot outside). Fortunately there are other options
for bringing fresh air into your home. A certied contractor can help
you get all the energy savings and comfort possible from a well sealed
home, along with the safety of proper ventilation.
Your house is a system and every component in it works together.
Adding insulation and sealing air leaks can improve the energy
efciency of your home and improve your home’s comfort and
durability. However, every change you make to the building’s
envelope (walls, oors, and ceiling) and components will affect how
the home works to keep out the elements and keep your family
safe and comfortable. Tightening the building envelope without
providing appropriate ventilation can cause pressure imbalances
or negative pressure in the house. This negative pressure can set
up the conditions for backdrafting of replaces or fuel-burning
(combustion) appliances and may draw pollutants into the home.
A trained contractor understands how systems work together to
keep your house operating as it should.
This guide gives homeowners tips on where to nd a good
contractor, how to get your home tested for airtightness, where the
biggest air leaks usually are and how to x them, what the potential
health and durability concerns are, and how your contractor can
handle these concerns—in short, what you need to know to proceed
with condence to a more comfortable, energy-efcient, and healthy
home for your family.
If you are a contractor, share this guide with your customers so that
they can understand the process you will follow to make their home
more comfortable, durable, and energy efcient. See the references in
this guide for detailed explanations of air sealing techniques.
Insulation is like a fuzzy wool sweater on a
winter day. It will certainly keep you warm
if the air is calm. But, if the wind picks
up, you are going to need a windbreaker
to keep the breeze from carrying away
the heat. Air sealing is like adding the
windbreaker. It keeps the conditioned
air where it belongs.
• Removepollutantsources,ifpossible.
• Avoidcombustion(fuel-burning)
appliancesthatdonotdirectlyvent
to the outdoors.
• Neverusenon-ventedcombustion
(e.g.,kerosene)heatersinside
the house.
• Fixwaterleaksandmoisture
management problems.
• Testforradonandcarbon
monoxidelevels.
• Provideadequateventilation.
Finding a Contractor
There are two nationally recognized energy certications for home
energy auditors and contractors: the Building Performance Institute
(BPI) Building Analyst certication and the Residential Energy
Services Network (RESNET) HERS Rater certication. Historically,
BPI certication has focused on understanding the building science
of retrotting existing homes and RESNET has focused on building
science in new home construction.
BPI is a nonprot organization that accredits auditors, contractors, and
other building professionals. Auditors or building analysts specialize in
evaluating building systems and potential energy savings in homes. The
certied BPI Building Analyst energy auditor has passed both written
and eld exams, and must recertify every three years. Contractors learn
about building systems and are trained to install energy-efciency
measures. For more information see www.BPI.org
A certied RESNET energy auditor is called a HERS Rater. HERS
(the Home Energy Rating System) provides a miles-per-gallon type
rating for expected energy consumption in homes based on computer
models. Each home receives a score that can be compared with other
new or existing homes—the lower the score, the more efcient the home.
More information about HERS can be found at www.natresnet.org.
An easy way to nd a certied contractor is through a national or
regional retrot program. One such program is Home Performance
with ENERGY STAR, a national program from the U.S.
Environmental Protection Agency and the U.S. Department of
Energy that promotes a comprehensive, whole-house approach to
energy-efciency improvements. To nd a Home Performance with
ENERGY STAR contractor for your area, go to www.energystar.gov
and click on the link for Home Performance with ENERGY STAR.
Next, click on the “locations” link for certied contractors in
your state. For cities and states without Home Performance with
ENERGY STAR contractors, you can nd lists of contractors
in your area who understand the building science whole-house
approach through the BPI and RESNET websites: www.bpi.org
or www.natresnet.org
Many local, state, and federal entities offer grants and tax credits for
energy-efcient home improvements. Check with your local utility or
city, or check the DOE-sponsored Database of State Incentives for
Renewables and Efciency (DSIRE) at www.dsireusa.org. This site
is frequently updated and is a wealth of information, organized by
state, on state, local, utility, and federal incentives, tax credits, and
policies that promote renewable energy and energy efciency.
Certified contractors are trained in
building science principles to know
thesafestandmosteectivewaysto
improveyourhome’senergyeciency.
Test-In/Test-Out
If you are participating in a home performance or weatherization
program, one of the rst steps may be an energy audit. Depending
on the program, this audit may be conducted by an independent
auditor or by a weatherization contractor. Details will vary by
location and program, but here is what you can typically expect.
First, the contractor or auditor should inspect, evaluate, and analyze
your home. This step is commonly called an audit, but that term has
been around for a long time and can mean many things. Perhaps the
most important part of the audit is the conversation between the
occupants and the auditor. Be prepared to talk about comfort issues
and energy bills.
Here is what your audit should include:
•
The auditor may measure your house and
identify square footage, window area, door area, and the condition
of insulation, mechanical equipment, and air leaks.
•
The auditor will use diagnostic equipment
to measure how your house performs in ways that cannot be
seen by eyes alone. These tests may include a blower door test,
duct pressurization testing, infrared cameras and smoke sticks,
combustion safety testing, and carbon monoxide sampling.
A heating and cooling contractor may evaluate your furnace
and air conditioning system supply and return air balance.
More information on these tests is included in the next section.
•
The auditor
will estimate the costs of installing the measures and use a computer
program to estimate the expected energy savings. The cost of the
measures divided by the annual savings will tell you the “simple pay
back” or how many years the measures will take to pay for themselves.
Often investments in energy efciency provide a better return than
stocks, bonds, or savings accounts, while improving comfort.
•
Expert visual inspections
and tests can identify safety and operational problems that may
require attention before any other work on the house proceeds.
Combustion safety issues must be addressed before air sealing
begins. Auditors should also point out any obvious sources of
indoor air pollution. Dry rot and moisture problems must
be repaired.
Your contractor may test duct leakage as
partofthehome’senergyaudit.
1 Audit
2 Installing Air Sealing Measures
3TestingOut
• The house has active knob and
tube wiring-Rewirethehouserst.
• The house has vermiculite insulation -
Vermiculite insulation may contain asbestos.
Contact your state department of health.
• Bathroom fans are vented into the attic-
Vent fans to outside.
• The house has a leaking roof -Repairthe
roof leak before air sealing and insulating.
(Lstiburek2010)
Within a week or so, your home performance contractor should
analyze the test results and provide you with a detailed proposal
including a prioritized list of energy-efciency measures, packaged
options, and cost estimates. Critical safety or health issues should
be dealt with before work proceeds on the agreed-upon energy-
efciency improvements. Your contractor understands state and
local building codes and will work with code ofcials when necessary
to ensure that the improvements meet building code requirements.
Your contractor may bring in specialized subcontractors if needed.
Testing out means repeating some of the tests used at the beginning
of the audit process now that the installation is complete. Final
testing veries that renovations have improved the home’s
performance and that safety standards have been met. Some
contractors offer a guaranteed level of energy savings on their
retrot projects. Homeowners receive a report summarizing the
improvements completed, test results, and estimated energy savings.
In addition to testing out, in Home Performance with ENERGY
STAR, at least 1 in 20 homes is spot-checked by independent third-
party building professionals to ensure program compliance.
(left) Auditors will check for dry rot and
moisture problems as well as air leakage.
(middle)Yourcontractorwillvisually
inspect the home and test for safety
concerns before air sealing begins.
(right)Oncesafetyandhealthissues
havebeenaddressed,yourcontractor
will proceed with air sealing measures.
Auditors use forms like this one from Energy
TrustofOregonfortest-inandtest-out.
Diagnostic Tools for Test-In and Test-Out
A trained contractor may run these and other diagnostic tests on
your home as part of the test-in and test-out process.
High-efciency combustion appliances are usually sealed combustion,
meaning that they draw in oxygen from outside the home through a
dedicated vent and send exhaust fumes outside through a separate,
dedicated vent pipe. These exhaust ues are sealed to prevent backdraft-
ing, where exhaust fumes come back down the ue into the living space.
Older and less efcient combustion appliances are sometimes
atmospheric vented, meaning they draw combustion air from the
room in which they are located, often through an opening at the base
of the exhaust pipe. Auditors or contractors will check combustion
appliances such as stoves, furnaces, water heaters, and replaces for
carbon monoxide levels, backdrafting, and other safety hazards, such
as gas leaks and cracked heat exchangers. If problems are identied,
no air sealing occurs until the problem is xed. These may be serious
safety problems; in rare instances, occupants may need to leave the
house until problems are repaired.
A blower door uses a calibrated fan to measure how much air a
home leaks. The blower door mounts into an exterior door frame.
The fan pulls air out of the house, lowering the air pressure inside.
Outside air then ows into the house through all unsealed cracks
and openings. The amount of fan pressure required by the fan to
maintain the test pressure tells the auditor how much leakage the
house has. Some contractors will seal simple air leaks as they
are identied while the blower door is operating.
An infrared camera produces images called thermographs that show
variations in temperature not visible to the human eye. Infrared
cameras can be used during blower door tests to capture images
of temperature differences that can indicate air leakage or other
conditions such as gaps in insulation and overheating circuits.
Leaky ducts in attics or crawlspaces can account for 20% or more
of a home’s heating and cooling energy losses. A Duct Blaster (duct
pressurization test) uses a calibrated fan to test the air leakage rate
in air ducts. Another approach uses a blower door and a shallow
pan (a pressure pan) to cover each register and grill to measure and
prioritize duct leaks.
(top) Your contractor can use a blower
doortomeasureoverallhouseairleakage.
(bottom)Theinfraredcamerascanshow
airleaksnotvisibletothenakedeye.
If initial testing or inspections
identify any health or safety
problems, no air sealing occurs
until the problem is fixed.
Safety and Health Issues
Inspection and testing can identify health and safety issues
that should be xed before any air sealing or other efciency
improvements are made. Taking care of these issues is important to
your family’s health, and these issues should be xed before doing
any home improvements. If the problems are severe, x them before
returning home. Here are some problems to watch for.
•
Air pressure imbalances between the outside
and inside or between rooms of the house can cause replaces,
furnaces, and other appliances that burn fuel (such as wood and
natural gas) to pull exhaust gases back into the house instead
of letting them vent up the ue. This situation is known as
backdrafting. Carbon monoxide (CO), a toxic gas without odor
and color, can backdraft into homes causing illness and death.
•
Combustion appliances may have a pilot light ame.
Backdrafting, air pressure imbalances, and mechanical problems
can cause the pilot to blow out, or worse, the ame can “roll out”
of the appliance, causing a house re.
•
If the home is not properly ventilated,
water vapor from showering, cooking, breathing, and burning fuels
can concentrate in the home increasing humidity levels. This can
lead to mold and mildew, dust mites, wood rot, material damage,
and subsequent health and structural problems.
•
Many homes contain hazardous substances
(such as cigarette smoke, volatile organic compounds and other
offgases from carpets, paints, nishes, and home electronics;
cleaning chemicals; and pesticides) as well as allergens (such as
pet dander and dust mites). It is important to avoid or exhaust
pollutants at their source. Also, air pressure imbalances between
the outside and inside of the house can draw in pollutants from
outside. These can include solvents and car exhausts from attached
garages or radon emanating from the soil.
•
Radon is a naturally occurring radioactive gas. Radon
gas is colorless, odorless, and tasteless and cannot be detected by
human senses. In some geographic areas with high concentrations
of radon in the soil, it can accumulate in the home and may
adversely affect human health.
(top) Studies show homes and garages
maycontainover150householdproducts
that may be harmful to humans.
(bottom)Lackofventilation,poormoisture
management, installation issues, and
pressure imbalances combine leading to
mold problems inside walls.
All combustion appliances should be
testedforbackdrafting.Replacenatural
draft combustion appliances with
sealed combustion, induced draft, or
power-ventedappliances,ifpossible.
Homes with combustion appliances
shouldhavecarbonmonoxide
detectorsthatmeetUL2034.
Ventilate it Right
Studies show the average American spends up to 90% of their time
indoors. About 23 million people including 6.8 million children in the
United States now suffer from asthma. Some see a correlation and
point to indoor air pollutants—chemicals, gases, mold, dust, etc.—
as a culprit. To provide fresh air in your older home, your contractor
may recommend adding mechanical ventilation.
An old adage for building scientists is “build tight, ventilate right.”
When air leaks in the home are sealed up, mechanical ventilation
may need to be added.
There are several options for mechanical ventilation systems. Spot
ventilation, using exhaust-only fans in the kitchen and bathroom,
removes water vapor and pollutants from specic locations in the
home, but does not distribute fresh air. Balanced ventilation systems,
like air-to-air exchangers, heat-recovery ventilators, and energy-
recovery ventilators, both supply and exhaust air. Your contractor
can help you determine which one is most appropriate for your
specic climate, house design, and budget.
Ventilation Type Pros Cons
(airisexhausted
from the house
withafan)
• Easy to install
• Simple method for
spotventilation
• Inexpensive
•
Negativepressuremay
cause backdrafting
•
Makeup air is from
random sources
•
Removesheatedor
cooled air
(airissuppliedinto
thehousewithafan)
• Does not interfere with
combustion appliances
•
Positivepressuresinhibit
pollutants from entering
•
Deliversto
important locations
•
Doesnotremoveindoor
air pollutants at their
source
•
Brings in hot or cold air
or moisture from outside
•
Air circulation can
feel drafty
•
Furnacefanrunsmore
often unless fan has an
ECM(variable-speedmotor)
(heatandenergy
recoveryventilators)
• Nocombustionimpact
• Noinduced
inltration/exltration
• Can be regulated to
optimize performance
•
Providesequalsupply
andexhaustair
• Recoversupto80%ofthe
energyinairexchanged
• More complicated design
considerations
•
Overventilationunless
the building is tight
•
Cost
Heat-recoveryventilators(HRVs)and
energy-recovery(orenthalpy-recovery)
ventilators(ERVs)bothprovidea
controlledwayofventilatingahome
while minimizing energy loss by using
conditionedexhaustairtowarmorcool
freshincomingair.Therearesomesmall
wall-orwindow-mountedmodels,but
themajorityarecentral,whole-house
ventilationsystemsthatsharethefurnace
ductsystemorhavetheirownductsystem.
ThemaindierencebetweenanHRVand
anERVisthewaytheheatexchanger
works.WithanERV,theheatexchanger
transferswatervaporalongwithheat
energy,whileanHRVonlytransfersheat.
TheERVhelpskeepindoorhumidity
moreconstant.However,inveryhumid
conditions,theERVshouldbeturnedo
when the air conditioner is not running.
Air-to-airheatexchangersorheatrecovery
ventilators(HRV’s)arerecommended
for cold climates and dry climates.
Energyrecoveryventilators(ERV’s)are
recommended for humid climates.
Mostenergyrecoveryventilationsystems
canrecoverabout70%–80%oftheenergy
intheexitingair.Theyaremostcost
eectiveinclimateswithextremewinters
or summers, and where fuel costs are
high.Energyrecoveryventilationsystems
operatedincoldclimatesmusthave
devicestohelppreventfreezingand
frost formation.
Toolittleventilationcanleadtoindoor
airqualityproblems,toomuchcanwaste
energy and cause comfort issues. Your
contractorwilluseASHRAEStandard62.2
and other industry guidelines to determine
howmuchpassiveandmechanical
ventilationisrightforyourhome.
New Code Air Sealing Requirements
The 2009 International Energy Conservation Code (IECC) and
the 2009 International Residential Code (IRC) have several new
mandatory requirements for air sealing in new construction and
additions. These codes apply to new construction where adopted by
local jurisdictions. In general, these requirements do not apply to
retrot projects unless the project adds living space to the building
or changes the building’s energy load. The existing, unaltered
portions of the structure are not required to comply with all of the
requirements of the 2009 IECC or IRC. However, Building America
recommends implementing these requirements in existing portions
of your home wherever they are applicable and your budget allows
or health and safety concerns make them necessary.
The requirements regarding new buildings can be summarized in
this section excerpted from IECC, Chapter 4, Section 402.4, Air
Leakage (mandatory) (quoted verbatim). Builders can see IECC
2009, Chapter 4 “Residential,” and IRC 2009, Chapter 11 “Energy
Efciency,” for more details:
“The building thermal envelope shall be durably sealed to
limit infiltration. The sealing methods between dissimilar materials
shall allow for dierential expansion and contraction. The following
shall be caulked, gasketed, weather stripped or otherwise sealed
with an air barrier material, suitable film, or solid material:
1. all joints, seams and penetrations,
2. site-built windows, doors, and skylights,
3. openings between window and door assemblies and their
respective jambs and framing,
4. utility penetrations,
5. dropped ceilings or chases adjacent to the thermal envelope,
6. knee walls,
7. walls and ceilings separating a garage from conditioned spaces,
8. behind tubs and showers on exterior walls,
9. common walls between dwelling units,
10. attic access openings,
11. rim joists junction,
12. other sources of infiltration.”
Theholesinthesillplatewereproperlyair
sealed during construction of this house.
An Air Sealing Checklist
This section provides descriptions of the areas of the home most
likely to have air leakage, when to address those problems, durability
and health concerns related to the problems, and references for more
information. Additional information on how to identify and x
these problems and other building science information can be found
in the Building America Best Practices guides produced by DOE
and available for free download at www.buildingamerica.gov. Work
with your contractor to determine which of these measures are most
needed and most cost-effective.
Common air sealing trouble spots are shown on the graphic below
and listed on the following page. Each of these trouble spots is
described further in the pages that follow.
Contractors, see the references in the
sections below for detailed descriptions
ofairsealingtechniquesandtechnologies.
BuildingAmericaresearchidenties19keyareaswhereairsealingcanimprovea
home’senergyeciency,comfort,andbuildingdurability.Theinformationinthis
guide can help you find a certified home performance contractor and work with
your contractor to identify problem areas, prioritize projects with safety in mind,
andstartsealingtheairleaksinyourhomeforcost-eectiveenergysavings.
1. Air Barrier and Thermal
Barrier Alignment
2. Attic Air Sealing
3. Attic Kneewalls
4. Shaft for Piping or Ducts
5. Dropped Ceiling/Sot
6. Staircase Framing at Exterior Wall
7. Porch Roof
8. Flue or Chimney Shaft
9. Attic Access
10. Recessed Lighting
11. Ducts
12. Whole-House Fan
13. Exterior Wall Penetrations
14. Fireplace Wall
15. Garage/Living Space Walls
16. Cantilevered Floor
17. Rim Joists, Sill Plate, Foundation, Floor
18. Windows & Doors
19. Common Walls Between
Attached Dwelling Units
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
18
15 19
3
13
18
16
17
5
4
14
9
13
6
1
8
17
17
10
12
13
7
11
2
Air Barrier Completion Guidelines
1.AirBarrierandThermalBarrierAlignment Airbarrierisinalignmentwiththethermalbarrier(insulation).
2.AtticAirSealing Topplatesandwall-to-ceilingconnectionsaresealed.
3.AtticKneewalls Air barrier is installed at the insulated boundary
(kneewalltransitionorroof,asappropriate).
4.DuctShaft/PipingShaftandPenetrations Openingsfromattictoconditionedspacearesealed.
5.DroppedCeiling/Sot Air barrier is fully aligned with insulation; all gaps are fully sealed.
6.StaircaseFramingatExteriorWall/Attic Air barrier is fully aligned with insulation; all gaps are fully sealed.
7.PorchRoof Air barrier is installed at the intersection of the porch roof
andexteriorwall.
8.FlueorChimneyShaft Openingaroundueisclosedwithashing,andanyremaining
gapsaresealedwithre-ratedcaulkorsealant.
9.AtticAccess/Pull-DownStair Atticaccesspanelordrop-downstairisfullygasketedfor
anair-tightt.
10.RecessedLighting Fixturesareprovidedwithair-tightassemblyorcovering.
11.Ducts Allductsshouldbesealed,especiallyinattics,ventedcrawlspaces,
and rim areas.
12.Whole-HouseFanPenetrationatAttic Aninsulatedcoverisprovidedthatisgasketedorsealedtothe
opening from either the attic side or ceiling side of the fan.
13.ExteriorWalls Servicepenetrationsaresealedandairsealingisinplacebehind
oraroundshower/tubenclosures,electricalboxes,switches,and
outletsonexteriorwalls.
14.FireplaceWall Air sealing is completed in framed shaft behind the fireplace or at
fireplace surround.
15.Garage/LivingSpaceWalls Airsealingiscompletedbetweengarageandlivingspace.
Pass-throughdoorisweatherstripped.
16.CantileveredFloor Cantileveredoorsareairsealedandinsulatedatperimeter
or joist transition.
17.RimJoists,SillPlate,
Foundation,andFloor
Rimjoistsareinsulatedandincludeanairbarrier.Junctionof
foundationandsillplateissealed.Penetrationsthroughthebottom
platearesealed.Allleaksatfoundations,oorjoists,andoor
penetrationsaresealed.Exposedearthincrawlspaceiscoveredwith
ClassIvaporretarderoverlappedandtapedatseams.
18.WindowsandDoors Space between window/door jambs and framing is sealed.
19.CommonWallsBetween
Attached Dwelling Units
Thegapbetweenagypsumshaftwall(i.e.,commonwall)andthe
structural framing between units is sealed.
1. Air Barrier and
Thermal Barrier Alignment
The air barrier is in alignment with (touching) the
thermal barrier (insulation).
Convective loops can form in wall cavities if there are gaps between
the insulation and the air barrier. Convective loops (air movement
within the wall cavities caused by temperature differences) will
get cold air falling and hot air rising. This air movement reduces
the effectiveness of the insulation and can pull in outside air and
cause moisture problems. Arches, softs, chases, and other design
features create an uneven air barrier (drywall plane) that is difcult
to insulate thoroughly. Expect the contractor to inspect these areas
visually or with an infrared camera to make sure batts or blown
insulation completely ll wall cavities.
Thermal and air barrier alignment is not an issue with insulation
materials like spray foam or rigid foam that form an air barrier as
well as thermal barrier, as long as they form a continuous air barrier
from top to bottom and side to side. Spray foams should be sprayed
to a consistent minimum depth across the area to be sealed and
insulated. Rigid foam board that is serving as the air and thermal
barrier should be taped at the seams with housewrap tape and glued
with caulk at the edges to the wall framing, sill plate, or top plate.
Blown cellulose and blown or batt berglass insulation will not
stop air ow.
Figure1.1.(left)Cutberglassbattinsulationtotaroundelectricalboxesand
wiringorpipesthatrunthroughthewalls.Compressionsliketheseruinthebatt’s
thermalalignmentwithwallsandlessenitseectiveness.
Figure1.2.(right) Install batts to fit smoothly and to completely fill wall and ceiling
cavities.Hereberglassbattscompletelylljoistsofbasementceiling.
When replacing dry wall, replacing siding,
adding an addition, adding insulation to
attic or crawlspace or any time access
isavailable.
Convectiveloopsinwallscanpullin
pollen, dust, and moisture. Walls that
arenotwellinsulatedcanprovideacold
surfaceinwallcavitieswherewarmindoor
air can condense in winter and warm
outdoor air can condense in the summer,
encouraging mold growth in walls.
Requirement for New
Construction and Additions
• Exteriorthermalenvelopeinsulationfor
framed walls is installed in substantial
contact and continuous alignment with
buildingenvelopeairbarrier.
• Breaksorjointsintheairbarrierare
filled or repaired.
• Air-permeableinsulationisnotused
as a sealing material.
• Air-permeableinsulationisinside
of an air barrier.
• BuildingAmericaBestPractices
• U.S.DepartmentofEnergy2009b
• U.S.EnvironmentalProtection
Agency2008b
Caulk where drywall
meets top plate
Ceiling drywall taped
or caulked to wall drywall
2. Attic Air Sealing
Top plates and wall-to-ceiling connections are sealed.
Good air-sealing and a continuous air barrier between the attic and
the home’s conditioned (living) space are important not only to save
energy and reduce fuel bills, but also to prevent moisture problems
in the attic. Sealing holes in the attic makes chimneys and ues
work better because a leaky attic ceiling acts like a chimney and will
compete with the real chimney for air. Air sealing the leaky attic
ceiling also reduces the house’s “suction” (or stack effect) so less
contaminants are drawn up into the house from the ground such
as radon and other soil gases (Lstiburek 2010).
On the inside of the home, the ceiling drywall can serve as an air
barrier. Visible cracks at the seam of the wall and ceiling can be
taped, mudded, and painted or lled with paintable caulk, such as
silicon latex. Your contractor can determine where leaks are with
an infrared camera, by feeling for air ow, or by inspecting the
attic insulation. Dirty insulation is an indication that air is owing
through the insulation and pulling dust with it.
Your contractor may pull back or scoop out the insulation to apply
caulk, spray foam, or other sealant where the walls meet the attic
oor. Other places in the attic that often are big sources of air leaks
are softs (dropped-ceiling areas, duct chases, plumbing chase),
behind or under attic kneewalls, around recessed can lights, around
ue pipes, around ducts, and at attic hatches (see strategy #3, #4,
#5, #8, #9, #10, and #11).
When To Do This
When replacing dry wall, replacing siding,
adding an addition, adding insulation to
attic, anytime you see cracks at the inside
seam of the wall and ceiling. In vaulted
ceilings, the ceiling-to-wall intersection can
be accessed and sealed from the inside or
from the outside when reroofing occurs.
Durability & Health
Heat moves from high-temperature regions
to low-temperature regions. The warmer
the air, the more water vapor it can carry
with it. If warm, moist air gets into a cold
attic through leaks in the home’s thermal
envelope, it can condense on rafters and
other solid surfaces, which may lead to
water damage and mold growth.
2009 IECC/2009 IRC Code
Requirement for New
Construction and Additions
Ceiling/attic
Air barrier in any dropped ceiling/sot is
substantially aligned with insulation and
any gaps are sealed.
More Information
• BuildingAmericaBestPractices
• Lstiburek2010
• U.S.EnvironmentalProtection
Agency2008a
• U.S.EnvironmentalProtection
Agency2008c
Sprayfoam
top plate
to air seal
Figure2.2.Pullbackinsulationtoseal
drywall to top plate with spray foam, caulk,
orothersealer(Lstiburek2010).
Figure2.1.Sealthewalldrywallto
the top plate and ceiling drywall.
EXTERIOR TOP PLATE AT SOFFIT
Guide to Attic Air Sealing
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
fiberglass 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
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]
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.
Detail ready for insulation [3]
1.
2.
3.
Alternate Method
2a.
13 April 12, 2010
RETROFIT TECHNIQUES AND TECHNOLOGIES AIR SEALING
3. Attic Kneewalls
Air barrier is installed at the insulated boundary
(kneewall transition or roof, as appropriate).
Kneewalls, the sidewalls of nished rooms in attics, are often leaky
and uninsulated. Your contractor can insulate and air seal these
walls in one step by covering them from the attic side with sealed
rigid foam insulation. Your contractor can plug the open cavities
between joists beneath the kneewall with plastic bags lled with
insulation or with pieces of rigid foam. Another option is to apply
rigid foam to the underside of the rafters along the sloped roof line
and air seal at the top of the kneewall and the top of the sidewall,
which provides the benet of both insulating the kneewall and
providing insulated attic storage space.
Doors cut into kneewalls should also be insulated and airsealed by
attaching rigid foam to the attic side of the door, and using a latch
that pulls the door tightly to a weather-stripped frame.
Anytimeyouhaveaccesstokneewalls.
If warm moist air gets into a cold attic
throughleaksinthehome’sthermal
envelope,itcancondenseonraftersand
other solid surfaces, which may lead to
water damage and mold growth.
Requirement for New
Construction and Additions
Atticaccess(exceptunventedattic),
kneewall door, or drop down stair
is sealed.
• BuildingAmericaBestPractices
• IowaEnergyCenter2008
• Lstiburek2010
• U.S.DepartmentofEnergy2000a
• U.S.EnvironmentalProtection
Agency2008a
• U.S.EnvironmentalProtection
Agency2008b
• U.S.EnvironmentalProtection
Agency2008c
Seal
Attic living
space
Hardboard
Desired
ventilation
Option 1 Option 2
Seal air barrier at edges
Seal
Insulated Box
Drawers
Drawers
Figure3.1.Insulateandair
seal the kneewall itself, as
shown, or along the roof line
(Source:DOE2000a).
Figure3.2.Airsealoorjoist
cavitiesunderkneewallsby
llingcavitieswithberglass
batts that are rolled and stued
inplasticbags(asshownhere)
oruserigidfoam,OSB,orother
air barrier board cut to fit and
sealed at edges with caulk.
Figure3.3.Buildanairtight,
insulatedboxaroundany
drawers or closets built into
attickneewallsthatextendinto
uninsulated attic space. Insulate
alongairbarrier(shownin
yellowondrawing)oralongroof
linewithrigidfoam(Source:
IowaEnergyCenter2008).
4. Duct Shaft/Piping Shaft
and Penetrations
Openings from attic to conditioned space are sealed.
Any chases, shafts, or building cavities that contain piping or wiring
can serve as links between conditioned and unconditioned space.
Your contractor can inspect these areas and close the gaps with caulk,
spray foam, and blocking material (pieces of rigid foam, plywood, or
oriented strand board cut to t and sealed in place with spray foam).
Furnace ues require high-temperature-rated sealing materials.
Figure4.1.Sealatticandwallpenetrationsassociatedwith
mechanicalventilationsystems,electricalchaseopenings,anddropped
sots(Source:DOE2000a).
Anytimeyouhaveaccess.
HVAC, plumbing, and wiring chases can
bring conditioned air into attics, leading
tocondensationandmoldproblems.They
canalsoconnectcrawlspacesandliving
spaces bringing soil gases into the home.
Requirement for New
Construction and Additions
Duct shafts, utility penetrations, knee
wallsandueshaftsopeningtoexterior
or unconditioned space are sealed.
• BuildingAmericaBestPractices
• IowaEnergyCenter2008
• U.S.EnvironmentalProtection
Agency2008a
• U.S.EnvironmentalProtection
Agency2008c
• HouseEnergy2009
Seal with
Seal and insulate
sheet metal
dropped sot
and high-temp
caulk
Seal
chases
Caulk
electrical
fixtures to
drywall
Seal HVAC
penetrations
Seal electrical
penetrations
Seal
bottom
Seal plumbing
penetrations
plate
5. Dropped Ceiling/Soft
Air barrier is fully aligned with insulation;
all gaps are fully sealed.
Softs (dropped ceilings) found over kitchen cabinets or sometimes
running along hallways or room ceilings as duct or piping chases
are often culprits for air leakage. Your contractor will push aside
the attic insulation to see if an air barrier is in place over the
dropped area. If none exists, the contractor will cover the area
with a piece of rigid foam board, sheet goods, or reective foil
insulation that is glued in place and sealed along all edges with
caulk or spray foam, then covered with attic insulation. If the
soft is on an exterior wall, sheet goods or rigid foam board
should be sealed along the exterior wall as well. If the soft
contains recessed can lights, they should be rated for insulation
contact and airtight (ICAT) or a dam should be built around
them to prevent insulation contact.
Figure5.1.Placeasolidairbarrieroversotsasfollows:pullbackexisting
insulation;coverareawithairbarriermaterial(gypsum,plywood,OSB,rigid
foam,etc.);sealedgeswithcaulk;coverwithinsulation(Lstiburek2010).
Any time, if attic construction allows
accesstoareaabovesots.
If warm moist air gets into a cold attic
throughleaksinthehome’sthermal
envelope,itcancondenseonsolid
surfaces, which may lead to water
damage and mold growth.
Requirement for New
Construction and Additions
Airbarrierinanydroppedceiling/sot
is substantially aligned with insulation
and any gaps are sealed.
• BuildingAmericaBestPractices
• IowaEnergyCenter2008
• Lstiburek2010
• U.S.EnvironmentalProtection
Agency2008a
• U.S.EnvironmentalProtection
Agency2008b
• U.S.EnvironmentalProtection
Agency2008c
DROPPED SOFFITS (Bulkheads, Arches)
Guide to Attic Air Sealing
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
fiberglass 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
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].
Detail ready for insulation [3,4]
1.
2.
3.
4.
Sealant on gypsum and top plate
3/4”closureboard(OSB,plywood,
gypsumboard,rigidinsulation)
Continuousbeadofadhesive
around perimeter of closure board
6. Staircase Framing at
Exterior Wall/Attic
Air barrier is fully aligned with insulation;
all gaps are fully sealed.
If the area under the stairs is accessible, look to see if the inside wall
is nished. If not, have your contractor insulate it, if needed, and
cover it with a solid sheet product like drywall, plywood, oriented
strand board, or rigid foam insulation. Then, your contractor can
caulk the edges and tape the seams to form an air-tight barrier.
Stairs should be caulked where they meet the wall.
Figure6.1.Installanairbarrierandairsealingonexteriorwallsbehindstairs.
If the area behind the stairs is inaccessible, caulk stairs where they meet the wall.
Use caulk if the area is already painted; use tape and joint compound if area
will be painted.
Any time.
Uninsulatedexteriorwallswithnoair
barriers present a cold surface where
condensation and mold can form.
Requirement for New
Construction and Additions
• Exteriorthermalenvelopeinsulationfor
framed walls is installed in substantial
contact and continuous alignment with
buildingenvelopeairbarrier.
• Air-permeableinsulationisinsideof
an air barrier.
• BuildingAmericaBestPractices
• U.S.EnvironmentalProtection
Agency2008c
• HouseEnergy2009
Gypsum
board
Structural
sheathing
Tape and joint
compound seal
7. Porch Roof
Air barrier is installed at the intersection of the porch
roof and exterior wall.
If a test-in inspection identies air leakage at the wall separating
the porch from the living space, the contractor will investigate to
see if the wall board is missing or unsealed. If this is the case, the
contractor will install some type of wall sheathing (oriented strand
board, plywood, rigid foam board) cut to t and sealed at the edges
with spray foam. Your contractor will also make sure this wall
separating the attic from the porch is fully insulated.
Any time, if porch wall is accessible,
either from the attic or from the porch.
Coldsurfacesintheexteriorwall
encourage condensation and mold. If the
air barrier is missing, wind can carry dust
andpollenintothelivingspace.
Requirement for New
Construction and Additions
• Exteriorthermalenvelopeinsulationfor
framed walls is installed in substantial
contact and continuous alignment with
buildingenvelopeairbarrier.
• Breaksorjointsintheairbarrierare
filled or repaired.
• Air-permeableinsulationisinsideof
an air barrier.
• BuildingAmericaBestPractices
• Moriarta2008
• U.S.EnvironmentalProtection
Agency2008b
Studies Show
StevenWinterAssociates,aBuildingAmericaresearchteamlead,used
ablowerdoortestandinfraredcamerastoinvestigatehigh-energybill
complaintsata360-unitaordablehousingdevelopmentandfoundnearly
twicetheexpectedairleakage.Infraredscanningrevealedanairleakage
pathonanexteriorsecond-storywallaboveafrontporch.StevenWinter
Associates found that, while the wall between the porch and the attic had
beeninsulatedwithunfacedberglassbatts,wallboardhadneverbeen
installed.Theinsulationwasdirtyfromyearsofwindwashingaswind
carried dust up through the perforated porch ceiling, through the insulation,
intotheatticandintothewallabove.Crewsusedrigidfoamcuttotand
gluedinplacewithexpandablesprayfoamtosealeacharea.Blowerdoor
testsshowedthechangereducedoverallenvelopeleakageby200CFM
50
.
Atacostof$267perunit,thisxresultedinsavingsof$200peryearper
unit, for a payback of less than two years.
Figure7.1.Whenresearcherspulledbacktheporchceiling,theyfound
thewallboardwasmissingsonothingwascoveringtheinsulationonthis
exteriorwall.Anairbarrierofrigidfoamboardwasputinplacewithspray
foam(Source:Moriarta2008).
8. Flue or Chimney Shaft
Opening around ue is closed with ashing, and any
remaining gaps are sealed with re-rated caulk or sealant.
There are often gaps around chimneys, furnaces, and water heater
ues that allow conditioned air to ow up into the attic. Your
contractor can seal this gap with lightweight aluminum ashing
(sheet metal) and special high-temperature (heat-resistant) caulk. A
metal dam should be used to
keep insulation away from the
ue. The same technique is
used for masonry chimneys.
Figure8.1.
Step1:Cutaluminumashing
totaroundue.
Figure8.2.
Step2:Sealashingtopipewith
high-temperaturecaulk.
Figure8.3.
Step3:Formaninsulationdamto
keep the insulation from coming
intocontactwiththeuepipe.
Anytimetheuepipeisaccessible
in the attic.
Use the right sealing products and
techniquestokeepammablematerials
fromtouchinghotues.
Requirement for New
Construction and Additions
Duct shafts, utility penetrations, knee
wallsandueshaftsopeningtoexterior
or unconditioned space are sealed.
• BuildingAmericaBestPractices
• U.S.EnvironmentalProtection
Agency2008a
• U.S.EnvironmentalProtection
Agency2008c
SEALING ATTIC AIR LEAKS
Furnace Flues Require Special Sealing Techniques
The opening around a furnace or water heater flue or chimney can be a major source of
warm air moving in the attic. Because the pipe gets hot, building codes usually require
1 inch of clearance from metal flues (2 inches from masonry chimneys) to any combustible
material, including insulation. Photos 5 and 6 show how to seal this gap with lightweight
aluminum flashing and special high-temperature (heat-resistant) caulk. Before you push
the insulation back into place, build a metal dam (photo 7) to keep it away from the pipe.
Use the same technique for masonry chimneys.
5. CUT ALUMINUM FLASHING
14” ALUMINUM
FLASHING
OPEN JOIST
CAVIT
Y
HIGH-TEMP
CAULK
CLASS B
FURNACE FLUE
Caution: Furnace flues (the
pipe that removes your furnace
exhaust) can be very hot.
Cut aluminum flashing to fit around the flue. For
round flues, cut half circles out of two pieces so
they overlap about 3 inches in the middle. Press
the flashing metal into a bead of high-temperature
caulk and staple or nail it into place. If there’s no
wood, staple or nail it directly to the drywall, but
be sure not to staple or nail through the drywall.
6. SEAL WITH SILICONE CAULK
HIGH-TEMP
CAULK
Seal the gap between the flue and metal flashing
with special high-temperature caulk. Don’t use
spray foam.
Identifying Attic Pipes
7. FORM AN INSULATION DAM
INSULATION DAM
1” TABS
RENT IN
STAPLE
DOWN
2” TABS
BENT OUT
Form an insulation dam to prevent insulation from
contacting the flue pipe. Cut enough aluminum from
the coil to wrap around the flue plus 6 inches. Cut
slots 1 inch deep and a few inches apart along the
top and bend the tabs in. Cut slots about 2 inches
deep along the bottom and bend out the tabs. Wrap
the dam around the flue and secure the bottom by
stapling through the tabs. Now put insulation back
right up against the dam.
FLUES/VENTS/PIPES: MADE OUT OF: SEAL AROUND WITH:
Furnace/Water Heater Galanized Metal
Aluminum flashing and high-
temperature silicone caulk
Aluminum flashing and high-
Chimney Masonry/Metal
temperature silicone caulk
Expanding foam or caulk,
Plumbing Cast Iron or PVC
depending on size of gap
1.8 SEALING ATTIC AIR LEAKS
1.9 SEALING ATTIC AIR LEAKS
SEALING ATTIC AIR LEAKS
Furnace Flues Require Special Sealing Techniques
The opening around a furnace or water heater flue or chimney can be a major source of
warm air moving in the attic. Because the pipe gets hot, building codes usually require
1 inch of clearance from metal flues (2 inches from masonry chimneys) to any combustible
material, including insulation. Photos 5 and 6 show how to seal this gap with lightweight
aluminum flashing and special high-temperature (heat-resistant) caulk. Before you push
the insulation back into place, build a metal dam (photo 7) to keep it away from the pipe.
Use the same technique for masonry chimneys.
5. CUT ALUMINUM FLASHING
14” ALUMINUM
FLASHING
OPEN JOIST
CAVIT
Y
HIGH-TEMP
CAULK
CLASS B
FURNACE FLUE
Caution: Furnace flues (the
pipe that removes your furnace
exhaust) can be very hot.
Cut aluminum flashing to fit around the flue. For
round flues, cut half circles out of two pieces so
they overlap about 3 inches in the middle. Press
the flashing metal into a bead of high-temperature
caulk and staple or nail it into place. If there’s no
wood, staple or nail it directly to the drywall, but
be sure not to staple or nail through the drywall.
6. SEAL WITH SILICONE CAULK
HIGH-TEMP
CAULK
Seal the gap between the flue and metal flashing
with special high-temperature caulk. Don’t use
spray foam.
Identifying Attic Pipes
7. FORM AN INSULATION DAM
INSULATION DAM
1” TABS
RENT IN
STAPLE
DOWN
2” TABS
BENT OUT
Form an insulation dam to prevent insulation from
contacting the flue pipe. Cut enough aluminum from
the coil to wrap around the flue plus 6 inches. Cut
slots 1 inch deep and a few inches apart along the
top and bend the tabs in. Cut slots about 2 inches
deep along the bottom and bend out the tabs. Wrap
the dam around the flue and secure the bottom by
stapling through the tabs. Now put insulation back
right up against the dam.
FLUES/VENTS/PIPES: MADE OUT OF: SEAL AROUND WITH:
Furnace/Water Heater Galanized Metal
Aluminum flashing and high-
temperature silicone caulk
Aluminum flashing and high-
Chimney Masonry/Metal
temperature silicone caulk
Expanding foam or caulk,
Plumbing Cast Iron or PVC
depending on size of gap
1.8 SEALING ATTIC AIR LEAKS
1.9 SEALING ATTIC AIR LEAKS
SEALING ATTIC AIR LEAKS
Furnace Flues Require Special Sealing Techniques
The opening around a furnace or water heater flue or chimney can be a major source of
warm air moving in the attic. Because the pipe gets hot, building codes usually require
1 inch of clearance from metal flues (2 inches from masonry chimneys) to any combustible
material, including insulation. Photos 5 and 6 show how to seal this gap with lightweight
aluminum flashing and special high-temperature (heat-resistant) caulk. Before you push
the insulation back into place, build a metal dam (photo 7) to keep it away from the pipe.
Use the same technique for masonry chimneys.
5. CUT ALUMINUM FLASHING
14” ALUMINUM
FLASHING
OPEN JOIST
CAVIT
Y
HIGH-TEMP
CAULK
CLASS B
FURNACE FLUE
Caution: Furnace flues (the
pipe that removes your furnace
exhaust) can be very hot.
Cut aluminum flashing to fit around the flue. For
round flues, cut half circles out of two pieces so
they overlap about 3 inches in the middle. Press
the flashing metal into a bead of high-temperature
caulk and staple or nail it into place. If there’s no
wood, staple or nail it directly to the drywall, but
be sure not to staple or nail through the drywall.
6. SEAL WITH SILICONE CAULK
HIGH-TEMP
CAULK
Seal the gap between the flue and metal flashing
with special high-temperature caulk. Don’t use
spray foam.
Identifying Attic Pipes
7. FORM AN INSULATION DAM
INSULATION DAM
1” TABS
RENT IN
STAPLE
DOWN
2” TABS
BENT OUT
Form an insulation dam to prevent insulation from
contacting the flue pipe. Cut enough aluminum from
the coil to wrap around the flue plus 6 inches. Cut
slots 1 inch deep and a few inches apart along the
top and bend the tabs in. Cut slots about 2 inches
deep along the bottom and bend out the tabs. Wrap
the dam around the flue and secure the bottom by
stapling through the tabs. Now put insulation back
right up against the dam.
FLUES/VENTS/PIPES: MADE OUT OF: SEAL AROUND WITH:
Furnace/Water Heater Galanized Metal
Aluminum flashing and high-
temperature silicone caulk
Aluminum flashing and high-
Chimney Masonry/Metal
temperature silicone caulk
Expanding foam or caulk,
Plumbing Cast Iron or PVC
depending on size of gap
1.8 SEALING ATTIC AIR LEAKS
1.9 SEALING ATTIC AIR LEAKS
(Source:EPA2008a)
Air seal gasket between
trim and panel
Insulation dams prevent loose-fill
insulation from falling through access
The hatch lid pushes up and
out of the way for access
Weatherstripping
Weatherstripping
Seal gap between frame
and rough opening with
caulk, backer rod, or foam
Panel
Insulation dams prevent
loose-fill insulation from
falling through access
The cover box pushes up and
out of the way for access
Air seal gasket between
trim and panel
Insulation dams prevent loose-fill
insulation from falling through access
The hatch lid pushes up and
out of the way for access
Weatherstripping
Weatherstripping
Seal gap between frame
and rough opening with
caulk, backer rod, or foam
Panel
Insulation dams prevent
loose-fill insulation from
falling through access
The cover box pushes up and
out of the way for access
9. Attic Access/Pull-Down Stair
Attic access panel or drop-down stair is fully gasketed
for an air-tight t.
A home’s attic access, which could be an attic hatch, pull-down
stairs, or a kneewall door, can leak a lot of heated or cooled air into
the attic if it is not sealed properly.
Your contractor can add weather stripping either to the frame or
panel of the attic access and may install latch bolts to ensure a
tighter seal. The hatch lid, stairs, or door should be insulated too.
If you are planning to add an attic access, consider the location. An
access hatch or pull-down stairs that is located in an unconditioned
part of the house, such as a garage, covered patio, or porch, does
not necessarily need to be air sealed or insulated. If your hatch
connects conditioned space like a bedroom, hallway, or closet to an
unconditioned attic, your contractor will check for air leakage.
Figure9.1.Insulateandairsealtheatticaccesshatchcover.
Figure9.2.Insulateandairsealthepull-downatticstair.
Any time.
Air sealing the attic access will minimize
theamountofmoisture-ladenairthat
escapes into the attic reducing the risk
of mold in the attic.
Requirement for New
Construction and Additions
Atticaccess(exceptunventedattic),knee
wall door, or drop down stair is sealed.
• BuildingAmericaBestPractices
• U.S.DepartmentofEnergy2000b
• U.S.DepartmentofEnergy2009a
• U.S.EnvironmentalProtection
Agency2008a
10. Recessed Lighting
Fixtures are provided with air-tight assembly or covering.
Recessed downlights are the most popular home lighting xture
in the United States. Older model recessed can xtures are energy
intensive in three ways—they are not approved for insulation
contact so insulation has to be kept at least 3 inches away all the way
around, leaving about 1 square foot of uninsulated ceiling space.
Most are using incandescent bulbs that use 3 to 5 times the power of
uorescents and add to air-conditioning loads. Third, the cans are
not airtight, so they allow conditioned air to escape from the living
area into unconditioned spaces such as attics.
If your home has non-airtight xtures, you can have a contractor
replace the whole xture with insulation contact-rated, air-tight
(ICAT) xtures, or caulk around the xture, under the trim ring if
caulking from inside the home. Other alternatives are to install the
recessed cans in an air-sealed dropped soft or to use surface-mounted
xtures instead. After air sealing, replace any incandescent lights in
the recessed lighting xture with low-wattage CFL or LED lamps.
Replaceolduninsulatedcanxtures
whenchanginglightingxtures;
can caulk any time.
Non-airtightrecessedcanxtures
can allow heated air to escape to attic
during winter, carrying moisture that
cancondenseinacoolattic.Theycan
also draw hot attic air into the home in
summer, pulling dust and insulation
particles into the home.
Requirement for New
Construction and Additions
Recessedlightxturesareairtight,IC
rated,andsealedtodrywall.Exception:
xturesinconditionedspace.
• BuildingAmericaBestPractices
• ASTM1991
• McCulloughandGordon2002
Figure10.1.(left) Replaceold,leakycan
xtureswithinsulated,airtightrecessed
lightxturesandcaulkthemwherethe
housing meets the drywall.
Figure10.2.(right) Seal cans to
preventheatedandcooledairfrom
leaking into attics as shown in this
infrared camera image.
Recessed light fixtures
should be rated for
insulation contact and
air tight (ICAT).
AIR TIGHTNESS
LABEL
Airtight wire
connection from
junction box
Airtight
can
Decorative
cover
Caulk
or Gasket
Studies Show
Old,leakyrecessedcansarelikeaholeintheceiling,onlyworse.Old
recessedcanswithincandescentbulbscanpull3to5timesasmuchairas
aholethesamesize,thankstothe“stackeect”—theheatinsidethecan
pullsairfromthehouseupintotheattic.Replacingaleakycanwithan
ICAT(insulationcontact-rated,air-tight)recesseddownlightwouldsavea
Phoenix,AZ,homeowner$1.56peryearincoolingcostsoraMinneapolis,
MN,homeowner$3.57peryearinheatingcosts(thesesavingsdon’teven
includethepossibleenergysavingsofCFLbulbsoverincandescentbulbs)
(McCulloughandGordon2002).
11. Ducts
All ducts should be sealed, especially in attics, vented
crawlspaces, and rim areas.
Repairing leaking ducts can yield big energy improvements. Duct
sealing contractors often nd more than just a few leaks: duct tape
dries and falls away; ducts may have been torn or crumpled by other
trades during installation; and poorly hung ducts can have bends
and kinks that prevent air from owing through them. It is not
uncommon to nd one or more ducts completely disconnected
from their register.
If return ducts in the heating and air-conditioning system have
holes, they can draw in hot attic air or cold outside air. As a result,
the system must work harder and use more energy to heat and cool
the inside of the house. In older homes, wall cavities and oor joist
cavities are sometimes used as return “ducts” to bring air from the
return registers back to the air handler unit, but these building
cavities are rarely air sealed.
A heating and cooling equipment contractor may
•
Inspect the duct system, including the attic and crawlspace.
•
Evaluate the system’s supply and return air ow.
•
Repair damaged and disconnected ducts.
•
Seal all leaks and connections with mastic (a thick sealant
painted on duct joints).
•
Seal all registers and grills to the ducts.
•
Insulate ducts in unconditioned areas (like attics, crawlspaces,
and garages) with duct insulation that has an R-value of
6 or higher.
•
Replace the lter as part of any duct system improvement.
•
Retest air ow after repairs are completed.
•
Ensure there is no backdrafting of gas or oil-burning appliances,
and conduct a combustion safety test after ducts are sealed.
Wheneverandwhereverducts
are accessible.
Unsealed ducts can draw in dust, moisture,
and contamination from unconditioned
spaces in the home. Broken ducts can
be a pathway for pests.
Requirement for New
Construction and Additions
HVAC register boots that penetrate
buildingenvelopearesealedtosuboor
or drywall.
• BuildingAmericaBestPractices
• BuildingScienceCorporation2006
• BuildingScienceCorporation2009d
• Cummingsetal.1990
• Granadeetal.2009
• JumpandModera1994
• Karinsetal.1997
• ORNL
• Shermanetal.2000
• U.S.EnvironmentalProtection
Agency2008a
• U.S.EnvironmentalProtection
Agency2009a
Figure11.2.Masticsealallsupplyandreturnairducts.
Studies Show
Inastudyofenergy-ecientmeasures,DOE’sEnergyInformation
Administration reported that sealing the ducts yielded by far the greatest
energysavingsofthe12measuresstudied,atthelowestcost(Granade
etal.2009).InaDOEstudyof100homesinPhoenix,Arizona,sealing
ductscutleakageby30%,savinghomeowners$80peryear.Astudyof
24Floridahomesfoundair-conditioningenergyusewasreducedby18%
afterductrepairsweremade(Cummingsetal.1990).Astudyofaretrot
projectinvolving25apartmentsinNewYorkfoundthatsealingtheHVAC
ductscutairowleakageby92CFMforsupplyductsand223CFMfor
returnductswithasimplepaybackof3to4years(Karinsetal.1997).
Researchonsixhomesinthesouthwestindicatedthat30%to40%of
thethermalenergydeliveredtotheductspassingthroughunconditioned
spaces is lost through air leakage and conduction through the duct walls.
Sealingandinsulatingtheductscutoverallductleakageapproximately
64%(JumpandModera1994).
REGISTER
Seal all joints in
boot and elbow
with mastic
Seal boots to sheet
goods with caulk,
mastic, or spray foam
Figure11.1.Paintmastic(athick,gooey
substance)ontotheductseams
andjoints.(Photosource:Habitatfor
HumanityLakelandFL).
DOE studies show duct
tape fails within months
(Sherman et al. 2000).
12. Whole-House Fan
Penetration at Attic
An insulated cover is provided that is gasketed or
sealed to the opening from either the attic side
or ceiling side of the fan.
A whole house fan is a fan installed in the ceiling to help quickly
cool the house by drawing air into the house through open windows
on summer mornings and evenings when the outside temperature
is lower than the indoor temperature. Ideally, the air should be
ducted to exhaust outside, not into the attic space. During the winter
months (and in summer when the air conditioner is running), the
whole house fan is not used. At those times, it represents a potential
energy loss because it is essentially a large, uninsulated hole in the
ceiling. Since standard fan louvers do not insulate or seal tightly, a
cover should be constructed or purchased to air seal and insulate this
hole from the attic side, the house side, or in case of very hot or cold
weather, both sides. Homeowners must remember to remove cover(s)
before operating the fan and to replace cover(s) during seasons when
the fan is not in use.
Figure12.2.Installaremovable,insulating,air-sealingcoveroveryourwhole
housefan(Source:SouthfaceEnergyInstitute1999).
When a whole house fan is installed.
Awholehousefancanpulllargequantities
of air from the home and, if windows are
not open, it can easily backdraft a fireplace
or combustion appliance located in the
home or attic. Some localities will not
permit a whole house fan to be installed if
a furnace is located in the attic or if there
is a combustion appliance in the home that
derivesitscombustionairfromeitherthe
attic or the inside of the home unless the
homeowner1)enclosesthecombustion
appliance so that it obtains combustion
airfromoutsidethehome;2)ductsthe
wholehousefandirectlytotheexterior;or
3)providesaswitchingdevicethatallows
onlyoneoftheappliances(fanorfurnace)
tobeonatatime(Davis2001).Thewhole
house fan should be ducted to the outside
oradequateventilationmustbeprovided
intheattictopreventtheatticfrombeing
overpressurizedandpushingatticdustinto
the house.
Requirement for New
Construction and Additions
Duct shafts, utility penetrations, knee
wallsandueshaftsopeningtoexterior
or unconditioned space are sealed.
• BuildingAmericaBestPractices
• Davis2001
• DOE1999
• SouthfaceEnergyInstitute1999
13. Exterior Walls
Service penetrations are sealed.
Your exterior walls may have a surprising number of holes in
them—for plumbing pipes and vents, electrical wires and conduits,
electrical xtures, clothes dryer ducts, and exhaust fans. Holes may
also have been drilled through the top and bottom plates; ideally,
these were caulked and sealed during construction as these areas are
nearly impossible to get to later, unless drywall or exterior sheathing is
being replaced. Your contractor will caulk penetrations through walls
from the exterior and interior. An ideal time to seal the drywall to the
suboor is when walls are being painted and baseplate trim is removed
(just pull back the carpet) or when oor covering is being replaced.
Sealwallpenetrationswheneveraccessible.
Sill-andtop-platepenetrationsmayonly
be accessible during construction of new
wallsoradditionsorwhenexterioror
interior wall sheathing is being replaced.
Electrical switches and outlets can be
accessed any time.
Unsealed penetrations can be a pathway
for dust and pests to enter the home.
Penetrationsthroughthetopplatemust
be sealed if the top plate is in the plane of
an intended air, smoke, or fire separation
(BSC2009).
Requirement for New
Construction and Additions
Duct shafts, utility penetrations, knee
wallsandueshaftsopeningtoexterioror
unconditioned space are sealed.
Showersandtubsonexteriorwalls
haveinsulationandanairbarrier
separatingthemfromtheexteriorwall.
Airbarrierextendsbehindboxesor
airsealed-typeboxesareinstalled.
• BuildingAmericaBestPractices
• BuildingScienceCorporation2006
• BuildingScienceCorporation2009e
• U.S.EnvironmentalProtection
Agency2008a
CAULK
Continuous bead of
sealant or adhesive
Thin sheet goods
as draft stop behind
tub or enclosure
Blocking
– TUB –
CAULK
Exhaust Fan
If fan exhausts or draws air
through sidewall, install hood
with louvered damper
Caulk around exterior
Figure13.2.Ifyouareremodelinga
bathroom make sure you seal and
insulate behind the tub or shower,
especiallyifitisonanexteriorwall.
Figure13.1.Caulkallplumbing
penetrationsthroughexteriorwalls.
Nailing
flange
Built-in
sealant
Select boxes with
built-in gasket
and sealant
Flange for sealing to
drywall air barrier
Figure13.3.Sealallelectricoutletsand
switcheswithfoamsealant,orselectboxes
withbuilt-insealantorgaskets.Install
foam gaskets between electrical outlets
or switches and their
coverplates,andinsert
plastic“child-safety”
plugs into the outlets to
furtherblockairow.
Figure13.4.Caulkaroundexhaust
fansattheceilingandexterior
wall.Alsocaulkaroundexterior
outletsandlightxtures.
Foam Gasket
14. Fireplace Wall
Air sealing is completed in framed shaft behind
the replace or at replace surround.
Fireplaces have many potential areas of air leakage. Air sealing
and insulation are often missing from the enclosure that forms a
prefabricated replace. There are often unsealed air gaps around the
ue and the surround. Flue dampers are not airtight, allowing air to
escape up the chimney even when no re is burning in the replace
(BSC 2009). A replace can actually waste more heat than it creates
(Iowa Energy Center 2008).
Even if you close the replace damper and it leaks just a little, a lot
of warm air from your home will be drawn up the chimney and be
replaced by cold air leaking into the house. If you use the replace,
follow these air sealing tips: (Iowa Energy Center 2008)
•
Every year, have the replace and chimney inspected and cleaned
by a certied chimney sweep.
•
Check the seal of the ue damper with an incense stick or piece of
burning paper. Seal around the damper assembly with refractory
cement, but don’t seal the damper closed. Replace warped or
missing dampers.
•
Use a removable plug like a chimney balloon that you insert in
the chimney above the damper and inate to plug air leaks when
you’re not using the replace. If you forget to remove it before
starting a re, it will react to the heat and quickly deate.
•
Install tight-tting glass doors.
•
Make a tight-tting air barrier to cover the replace opening
when not in use from rigid board insulation and plywood edged
with pipe insulation (Iowa Energy Center 2008).
•
Consider installing a sealed, natural gas or propane replace
insert. These inserts are sealed combustion and do away with
door and ue leaks.
At any time.
An open, unsealed fireplace carries risks of
backdraftingcarbonmonoxide,smoke,and
ash into the home. A sealed fireplace with
its own combustion air intake is preferred.
Homes that use gas or wood fireplaces
shouldhavecarbonmonoxidedetectors.
Requirement for New
Construction and Additions
Fireplacewallsincludeanairbarrier.
• BuildingAmericaBestPractices
• Brown1999
• BuildingScienceCorporation2009a
• DalicieuxandNicolas1990
• IowaEnergyCenter2008
• TyrolandPate2007
• U.S.EnvironmentalProtection
Agency2008a
Figure14.1.Airsealtheenclosure
surroundandue.
Studies Show
Studieshaveshownthatreplacedampersareoftenleftopen.Onestudy
showedfound80%ofreplacedamperswereinadvertentlyleftopen
(TyrolandPate2007).InaDOE-fundedstudyof56newhomesinArkansas
withgasorwoodreplaces,thereplacesaccountedfor5.3%oftotal
houseairleakage(Brown1999).
Seal
Solid air barrier
material sealed at
perimeter and seams
At any time.
Garagesoftencontainharmfulchemicals
and gases that must be kept out of the
livingspacebythoroughairsealingofany
common walls and ceilings.
Requirement for New
Construction and Additions
Airsealingisprovidedbetweenthe
garage and conditioned spaces.
• BuildingAmericaBestPractices
• AspenPublishers2000
• IowaEnergyCenter2008
• UniversityofIllinoisExtensionOce
• U.S.EnvironmentalProtection
Agency2010
15. Garage/Living Space Walls
Air sealing is completed between garage and living space.
Pass-through door is weather stripped.
For occupant health and safety, the garage should be completely air
sealed from the living areas of the house. When the garage is beneath a
second-story living space, the gaps created by the oor joists spanning
both the living space and the garage must be blocked off and sealed.
If the air handler for a central furnace must be located in the garage,
it should be in an air-sealed closet with its own air intake, so that it is
not drawing garage air to circulate through the house.
If you have an attached garage, expect your contractor to visually
inspect for cracks or improper sealing of the walls separating the
garage from the home, to test the seal tightness of doors linking the
garage with the rest of the home, to test carbon monoxide levels in the
house, to measure interface leakage between the garage and house,
and to determine what size garage exhaust fan, if any, is advisable.
Steps to a Healthier Garage – eliminate, isolate, ventilate.
Keep in mind the following:
1. Your very best option is to build a detached garage.
2. If that is not possible, try removing or isolating pollutants. Park
cars, mowers, etc., outside. Do not let cars or mowers idle in the
garage (and of course never start them with the garage door
closed). Start gas-powered mowers, leaf blowers, etc., outside.
Store paints, solvents, and other chemicals in tight containers.
Your contractor can assist you with the following recommendations:
3. Seal all penetrations through the common wall and ceiling. Use
gaskets, airtight drywall technique, etc., to make the common wall
and ceiling airtight.
4. Seal ducts located in the garage. (Avoid locating supply or return
registers in the garage when remodeling.)
5. Install a self-closing, insulated, metal, re-rated door with a good
weather seal between the living space and the garage.
6. Install a passive roof vent to keep the garage at a negative pressure
in relationship to the house. If needed, install a timed exhaust fan
that vents to the outside.
Figure15.1.Finishthewallsthatseparatethegaragefromtherestofthehome
with drywall that is sealed to the top and bottom plate with a bead of caulk.
Studies Show
Inaeldstudyof12homesinAnchorage,Alaska,researchersfoundthat
carbonmonoxide(CO)fromcarstartsinthegaragesenteredallbut1of
the12houses.FourofthehomescameclosetotheEPACOexposurelimit
and,inonecase,exceededit(AspenPublishers2000).Notedtheauthor:
“Inallbutonecase,thehousewasoperatingundernegativepressure
relativetothegarageduetothestackeect.Inotherwords,thehouse
wassuckingCOandotherairbornecontaminantsthroughthecommon
wallsandceilings.”TheresearchersfoundhighCOinhomeswhere
furnace ductwork was located in the garage and where the garage was
locatedunderoccupiedspaceabove.AstudybyHealthCanadaidentied
150dierentpollutantscommonlyfoundingarages.Preliminaryresults
from25housestestedinthatstudyfoundthatanaverageof13%ofall
infiltration into the houses was through the common wall between the
garage and house. A Minnegasco study measured typical leakage at an
evenhigher25%(Aspen2000).
Bottom plate caulked
or gasketed to subfloor
Drywall caulked, glued
or gasketed to top plate
GARAGE
15.2.Sealrimjoistsofthewallseparating
thehouse’slivingspacefromthegarage
with pieces of wall board and spray foam.
When comfort complaints or high utility
bills warrant it; if an infrared camera
inspectionrevealsthecantileveroor
to be a source of high leakage.
Ifacantileverisn’tproperlyairsealed
and insulated, moist air from the home
canpassintothecantileveroorcavity
and condense on the coldest surface it
nds—thebacksideofthesheathingor
bandjoist—causingmoldtogrowthere.
Requirement for New
Construction and Additions
Insulation is installed to maintain
permanent contact with underside of
suboordecking.Airbarrierisinstalled
atanyexposededgeofinsulation.
• BuildingAmericaBestPractices
• Lugano1998
• U.S.EnvironmentalProtection
Agency2008b
16. Cantilevered Floor
Cantilevered oors are air sealed and insulated at perimeter
or joist transitions.
Cantilevered oors, second-story bump-outs, and bay windows are
another area in the home that is often lacking proper air sealing.
The oor cavity must be lled with insulation with good alignment
(i.e., that is completely touching) the underside of the oor. The
interior and exterior sheathing needs to be sealed at the framing
edges. Blocking between oor joists should form a consistent air
barrier between the cantilever and the rest of the house. Continuous
sheathing, such as insulating foam sheathing, should cover the
underside of the cantilever, and be air sealed at the edges with caulk.
Figure16.1.Blockand
airsealboththeoor-
to-upperwalljunction
andtheoor-to-lower
wall junction.
Baseplate sealed
to subfloor
Blocking between joists,
sealed at perimeter
Insulation in continuous
contact with subfloor
17. Rim Joists, Sill Plate, Foundation,
and Floor
Rim joists are insulated and include an air barrier. Junction
of foundation and sill plate is sealed. Penetrations through
the bottom plate are sealed. All leaks at foundations,
oor joists, and oor penetrations are sealed. Exposed
earth in crawlspace is covered with Class I vapor retarder
overlapped and taped at seams.
The rim joist (also called a band joist) is the horizontal beam that
rests on top of the foundation wall or between oors. The oor joists
are attached to or run parallel with it. Rim joists are a particularly
troublesome area for air leakage. Several framing components
(foundation wall and sill plate or top plate, rim joist, and suboor
above) need to be connected and sealed to form a continuous air
barrier. Your contractor will inspect this area and, if needed, air seal
and insulate along the joints where the oor joists meet the rim joist
and the rim joist meets the suboor. The rim joist can be air sealed
and insulated with caulk and batt insulation, or rigid foam cut to
ll the space between each oor joist and sealed in place with spray
foam. Another option is to spray high- or low-density urethane
foam at each joist bay to cover the foundation wall-top plate-rim
joist-suboor connections.
Figure17.1.Usecaulkorsprayfoamtoairsealwherethefoundationwallmeets
the sill plate, where the sill plate meets the rim joist, and where the rim joist
meetsthesuboor.
Airsealingrimjoistsbelowtherstoor
can be done in conjunction with finishing
the basement, when insulating the
basementwalls,orwheneveranunsealed
rimjoistisaccessiblefrominside.Plywood
suboorseamscanbesealedwhen
replacingooringorreplacingor
installinginsulationbeneaththeoor.
Theinteriorsideoftherimjoistisacold
surface in wintertime; condensation can
form there if it is not properly insulated.
Adirtcrawlspaceoorshouldbecovered
withaClass1vaporretarder(e.g.,6-mil
polyethylene).Ifthehomehasanunvented
crawlspace,theundersideoftheoor
shouldbeairsealedandaventstackcan
be installed to minimize entry of soil gases
intolivingspace.
Requirement for New
Construction and Additions
Junctionoffoundationandsill
plate is sealed.
Corners and headers are insulated.
Rimjoistsareinsulatedandinclude
an air barrier.
Exposedearthinunventedcrawlspaces
iscoveredwithClassIvaporretarder
withoverlappingjointstaped.
Tape
Rim Joist
Seal outside if it can
be done without interfering
with drainage
Housewrap
Drywall
Bottom Plate
Caulk
Sill Plate
– Floor Joist –
Sill gasket
Subfloor
Studies Show
OnehomeownerinIllinoishadspentthousandsofdollarsre-sidinghis
house with rigid foam insulation, adding insulation, upgrading his furnace,
and replacing windows but his house was still drafty and his utility bills
werestillhigh.HecalledinaBPI-certiedcontractorwhoconductedseveral
assessmentsincludingablowerdoortestofthewholehouseandindividual
roomstodeterminewhereairwasleaking.Theblowerdoorshowedthe
home’sairleakagewasthreetimeshigherthanpreferred.Thecontractor
recommended plugging leaks in the crawlspace and rim joists; adding joist
insulation;air-sealingallplumbing,electrical,service,andductpenetrations;
andinsulatingandairsealingthecrawlspaceaccessandattichatchcover.
Theupgradescost$2,500andsavedthehomeowner$700ayearinenergy
costs(ConbereandFried2006).
• BuildingAmericaBestPractices
• BuildingScienceCorporation2009c
• ConbereandFried2006
• Braun1995
• BuildingScienceCorporation2009e
• Lstiburek2004a,b;2006;2008
• U.S.DepartmentofEnergy2000a
• U.S.EnvironmentalProtection
Agency2008b
• U.S.EnvironmentalProtection
Agency2009b
• U.S.EnvironmentalProtection
Agency2009c
Your contractor will seal the seams of the suboor plywood panels
if they are accessible. The contractor will also seal all holes that go
through the basement ceiling to the oor above, such as holes for
plumbing, HVAC ducts, and furnace vent pipes if the furnace is
located in the basement.
If your house’s foundation is a slab, your contractor can check
for and seal air leaks where the sill plate meets the foundation. If
your home has an unvented crawlspace your contractor will check
the foundation for cracks and holes that may need sealing. The
crawlspace access hatch should be weather stripped or gasketed. If
the crawlspace oor has exposed earth, this should be covered with
Class I vapor retarder with overlapping joints that are taped.
Air seal gasket
Crawlspace
Rigid insulation
Figure17.3.Airsealthecrawlspaceaccesshatchbyinstallingagasket
or weather stripping around the hatch edges.
Figure17.2.Sprayfoamalongthebasement
rimjoisttoprovideacompleteairbarrier
connecting the foundation wall, sill plate,
rimjoist,andsuboor(Source:BSC2009C).
18. Windows and Doors
Space between window/door jambs and framing is sealed.
When windows are installed in a new house, the rough opening (the
space left for the window) is typically 1.5 to 2 inches larger than the
window frame to give the installer room to install, plumb, and square
the window. The same is true of doors. Your contractor can properly
seal around the existing windows by removing the interior trim and
lling the rough opening with non-expanding foam or backer rod and
caulk. A simpler but more visible alternative is to leave the interior
trim in place and seal around it with a clear silicone caulk or paintable
latex caulk with silicone. Replace any cracked or loose panes. Consider
replacing older, single-pane windows that show signs of leakage, water
damage, or condensation with new double-pane windows installed
with proper air sealing and ashing.
Windows and doors should be weather stripped. See the DOE Energy
Savers website for a comprehensive description of different types
of caulking and weather stripping material www.energysavers.gov/
your_home/insulation_airsealing/index.cfm/mytopic=11260.
Older homes often have double-hung windows with chases hidden in
the wall for counter weights. Access these chases by removing the side
trim or by going through access ports along the sides of the window.
If the window is replaced, the weight should be removed and the
chases lled with insulation and sealed. If you have old windows with
working pulleys, the pulley holes can be air sealed but kept usable with
plastic caps called pulley seals. Doors should be self-closing and have
a tight tting sill.
Any time.
Moreecientwindowsmaybelessprone
to condensation and related mold growth.
Paintedwindowsashesandframesin
homesbuiltbefore1978maycontainlead-
basedpaint;useacontractorexperienced
inleadremoval.
Requirement for New
Construction and Additions
Space between window/door jambs
and framing is sealed.
• BuildingAmericaBestPractices
• BuildingScienceCorporation2009b
• Stovalletal.2007
• U.S.DepartmentofEnergy2000a
U.S.DepartmentofEnergy2009c
• U.S.EnvironmentalProtection
Agency2008b
Studies Show
AstudyconductedatOakRidge
NationalLaboratory’sBuildings
TechnologyCenteronwindow
air sealing showed that windows
with¾-inchrough-ingapshadan
equivalentleakageareaof28.2cm
2
/
m
2
. When the gap was caulked from
the interior side of the wall, the
equivalentleakageareawascutto
0.5cm
2
/m
2
(Stovall et al. 2007).
backer rod, caulk,
or nonexpanding foam
Use ENERGY STAR
labeled door
Install automatic
closer and gasket
or weatherstripping
Figure18.1.Usebackerrod,caulk,
ornonexpandingfoamapproved
for windows and doors to fill the
rough-ingaparounddoorsand
windows(DOE2000).
Figure18.2.Installautomaticcloser
and gasket or weather stripping
around doors. Caulk around trim.
19. Common Walls Between
Attached Dwelling Units
The gap between a gypsum shaft wall (i.e., common wall)
and the structural framing between units is sealed.
Common walls between units in multi-family housing (e.g.,
townhouses, duplexes, and apartments) should be constructed as
airtight assemblies for sound, smoke, re, and air quality control.
However, experience has shown that these common walls can often
be signicant sources of air and heat loss if gaps or cracks exist in the
connections between each unit’s walls. Your contractor can determine
whether this is a signicant source of air leakage in your home.
To reduce air leakage, this assembly should be air sealed at all
boundaries. Your contractor will seal wood frame walls with
reproof spray foam (EPA 2008). Masonry block party walls, which
form “chimneys” because of their porosity and open cores, can be
air sealed with two-component urethane foam, which also reduces
sound, odor transfer, and dust, insects, and moisture entry
(Braun et al. 1995).
Because these walls are re-rated assemblies for each unit, acceptable
materials for air-sealing common walls can vary signicantly
around the country. Your contractor will conrm with local code
ofcials which material is preferred for re safety reasons, prior
to retrotting. The contractor will seal all plumbing penetrations
through the drywall surface of common walls with re-rated sealant
materials (BSC 2009).
Figure19.1.Seal air gaps
between two framed common
walls (Source: Energy Services
Group, from EPA 2008)
Whenevercommonwallisaccessible.
Commonwallsbetweenunitsarere-rated
and should be air sealed and properly
blocked to minimize fire spread and entry
of air, moisture, and pests.
Requirement for New
Construction and Additions
Air barrier is installed in common
wall between dwelling units.
• BraunandWoods1995
• BuildingScienceCorporation2009e
• U.S.EnvironmentalProtection
Agency2008b
References
Aspen Publishers2000.“HowAttachedGaragesPoisonOurIndoorAir,AndWhatBuildersCanDoAboutIt.”inEnergy Design Update,Volume20,
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For information on Building America
visit www.buildingamerica.gov.
The website contains expanded
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Building America Program
George S. James • New Construction • 202-586-9472 • fax: 202-586-8134 • e-mail: Geor[email protected]v
Lew Pratsch • Existing Homes • 202-586-1512 • fax: 202-586-8185 • e-mail: Lew[email protected].gov
Building America Program • Oce of Building Technologies, EE-2J • U.S. Department of Energy •
1000 Independence Avenue, S.W. • Washington, D.C. 20585-0121 • www.buildingamerica.gov
Building Industry Research Alliance (BIRA)
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fax: 209-474-0817 • e-mail: Rob@consol.ws • www.bira.ws
Building Science Consortium (BSC)
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fax: 978-589-5103 • e-mail: Betsy@buildingscience.com • www.buildingscience.com
Consortium for Advanced Residential Buildings (CARB)
Steven Winter • Steven Winter Associates, Inc. • 50 Washington Street • Norwalk, CT 06854 •
203-857-0200 • fax: 203-852-0741 • e-mail: swinter@swinter.com • www.carb-swa.com
Davis Energy Group
David Springer • Davis Energy Group • 123 C Street • Davis, CA 95616 • 530-753-1100 • fax: 530-753-4125 •
e-mail: springer@davisenergy.com • deg@davisenergy.com • www.davisenergy.com/index.html
IBACOS Consortium
Brad Oberg • IBACOS Consortium • 2214 Liberty Avenue • Pittsburgh, PA 15222 • 412-765-3664 •
fax: 412-765-3738 • e-mail: bober[email protected] • www.ibacos.com
Industrialized Housing Partnership (IHP)
Philip Fairey • Florida Solar Energy Center • 1679 Clearlake Road • Cocoa, FL 32922 • 321-638-1005 •
fax: 321-638-1439 • e-mail: pfaire[email protected].edu • www.baihp.org
National Association of Home Builders (NAHB) Research Center
Tom Kenney • National Association of Home Builders (NAHB) Research Center •
400 Prince George’s Boulevard • Upper Marlboro, MD 20774 • 301-430-6246 •
fax: 301-430-6180 • toll-free: 800-638-8556 • www.nahbrc.org
National Renewable Energy Laboratory
Ren Anderson • 1617 Cole Boulevard, MS-2722 • Golden, CO 80401 • 303-384-7433 • fax: 303-384-7540 •
e-mail: ren_anderson@nrel.gov • www.nrel.gov
Tim Merrigan • 1617 Cole Boulevard, MS-2722 • Golden, CO 80401 • 303-384-7349 • fax: 303-384-7540 •
e-mail: [email protected]v • www.nrel.gov
Oak Ridge National Laboratory
Pat M. Love • P.O. Box 2008 • One Bethel Valley Road • Oak Ridge, TN 37831 • 865-574-4346 •
fax: 865-574-9331 • e-mail: lovepm@ornl.gov • www.ornl.gov
Pacific Northwest National Laboratory
Michael Baechler • 620 SW 5
th
, Suite 810 • Portland, OR 97204 • 503-417-7553 • fax: 503-417-2175 •
e-mail: [email protected]v • www.pnl.gov
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Research and
Development of Buildings
Our nation’s buildings consume
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transportation and industry.
Fortunately, the opportunities to
reduce building energy use—and
the associated environmental
impacts—are signicant.
DOE’s Building Technologies
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energy eciency of our nation’s
buildings through innovative new
technologies and better building
practices. The program focuses
on two key areas:
• Emerging Technologies
Research and development of
the next generation of energy-
ecient components, materials,
and equipment
• Technology Integration of new
technologies with innovative
building methods to optimize
building performance and savings
Visit our Web sites at:
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