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Air Sealing Attached Garage

    Scope
    Scope Images
    Image
    Air-seal and insulate the rim and band joists of walls separating an attached garage from the home’s conditioned space.
    Scope

    Ensure that the garage is separated from the conditioned space of the home by a continuous rigid air barrier.

    • Seal all seams, gaps, holes, and openings in the air barrier with caulk, foam, or a rigid air barrier material before installing the insulation.

    See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR, and Indoor airPLUS.

    Description
    Description

    Isolating attached garages from the living space is critical for preventing the potential infiltration of carbon monoxide and other contaminants into the dwelling. Open joist bays above the garage that extend into living spaces are an unwanted air pathway. Cracks between and around the boards of the rim joist, the top plate, and the sill plate-foundation wall intersections are other areas where air can flow through if seams aren’t adequately sealed. In addition, certain conditions in the home can cause the home to become depressurized, making it even more likely for garage air to be drawn into the home through leaks in and around the rim joists. Depressurization can occur when the house is airtight and an exhaust fan, range hood, clothes dryer, or combustion appliance is operated, if adequate makeup air is not provided to the house through a fresh air intake (a duct that brings outside air to the return side of the air handler).

    Walls and ceilings separating garages from conditioned spaces need to be sheetrocked (typically with 1/2-inch-thick Type X gypsum board) in accordance with local fire codes, but this is not the same as air sealing. All ceiling and wall penetrations (wiring, piping, ductwork, etc.) need to be sealed with appropriate sealants, such as caulk or canned spray foam. Or, a flash-and-batt approach can be used to insulate the garage ceiling and shared walls by spraying them with 2 inches of closed-cell spray foam, then filling the bays with fibrous batt insulation, as shown in Figure 1. All joist cavities that span between the garage and adjoining living spaces should be blocked with rigid material that is air-sealed in place or the framing should be designed so that rim joists or floor joists will serve as a naturally occurring air block at the shared wall. 

    Image
    Right - Walls and ceilings shared by the garage and living space must be air sealed and insulated.
    Right - Walls and ceilings shared by the garage and living space must be air sealed and insulated.
    Right - Walls and ceilings shared by the garage and living space must be air sealed and insulated.
    Figure 1. Walls and ceilings shared by the garage and living space must be air sealed and insulated (Source: Courtesy of Steven Winter Associates). 

    To provide an air barrier between the garage and the adjoining conditioned space, a solid air barrier material should be installed to-air seal joist bay openings spanning over the garage and conditioned space at the point above the wall separating the garage from the conditioned space. A rigid material like rigid foam board, drywall, OSB, or plywood can be cut to fit each joist bay opening (Figure 2). Each piece must be cut to fit then nailed and caulked or spray foamed into place, which is a labor-intensive process.

    Image
    Insert rigid blocking pieces into each joist bay and fasten with caulk or nails
    Insert rigid blocking pieces into each joist bay and fasten with caulk or nails
    Insert rigid blocking pieces into each joist bay and fasten with caulk or nails
    Figure 2. Insert rigid blocking pieces into each joist bay and fasten with caulk or nails (Source: Courtesy of Steven Winter Associates).

    If the garage shares only one wall with the home, ideally the framing would be designed so that ceiling joists above the garage run parallel to the shared wall so that a ceiling joist can serve as a solid air barrier above the shared wall (Figure 3). Where open bays will span the shared walls, the floor joists can be cut so that they terminate on either side of a rim joist installed above and aligned with the shared wall (Figure 4). At the base of the wall, the joints between the mud sill and rim joist at the foundation line of the shared garage-to-house wall should be sealed. The drywall separating the garage from the house should be sealed to the framing members at the top plate, bottom plate, corners, and seams.

    Image
    A continuous rim joist separates the garage and living space
    A continuous rim joist separates the garage and living space
    A continuous rim joist separates the garage and living space
    Figure 3. A continuous rim joist separates the garage from the living space (Source: Courtesy of PNNL). 
    Image
    The I-joist is continuous along the shared wall and serves as a natural air barrier between the garage and the house
    The I-joist is continuous along the shared wall and serves as a natural air barrier between the garage and the house
    The I-joist is continuous along the shared wall and serves as a natural air barrier between the garage and the house
    Figure 4. The I-joist is continuous along the shared wall and serves as a natural air barrier between the garage and the house (Source: Courtesy of Steven Winter Associates).

    For more information, see the guides Floor Above Garage, Garage Rim/Band joist Adjoining Conditioned Space, Air Sealing Doors Adjacent to Unconditioned Space, and Air Leakage Testing Garage to House Air Barrier.

    For multifamily buildings, see additional information about air-sealing garages in the guides Insulating Garages in Multifamily Buildings and Insulating Heated Garage Plenums in Multifamily Buildings. Similar principles apply when separating dwelling units at shared walls in multifamily buildings but additional measures are required, as described in the guide Air Sealing and Compartmentalization in Multifamily Buildings.

     

    HOW TO AIR-SEAL BETWEEN THE GARAGE AND LIVING SPACE

    1. Air-seal the rim joist of the wall shared by the garage and the house. (See the guide Garage Rim Band Joist for more details.)
      1. If the floor joist above a shared garage-living space wall runs parallel to the shared wall, the joist will provide an air barrier above the sealed wall. Seal any holes and seams in the joist to complete the air barrier.
      2. Where ceiling joists run perpendicular to the adjoining wall, one option is to install a continuous rim joist to separate the two areas with separate but aligned ceiling joists on each side of the rim joist (see Figure 3 and Figure 4).
      3. Another option is to install solid blocking material in the joist bays over the common wall. Cut rectangles of rigid blocking material (plywood, polyisocyanurate, extruded polystyrene, etc.) to fit each floor joist bay cavity. Install a backstop for the blocking material by tacking furring strips to the joists in-line with the foundation or house wall. Insert rigid pieces into each joist bay and fasten with caulk or nails (Figure 5). When using I-joists, make sure to cut the air blocking material to fit the irregular shape of the opening. If using open web floor trusses, seal any holes in the open-web floor trusses at the shared wall, if needed (Figure 6). Use caulk or spray foam to air-seal all four edges in each bay (Figure 7). Make sure to completely air seal around the rigid air barrier to prevent moist air from reaching and condensing on the rim joist.
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    When using I-joists, make sure to fill in the gaps on each side of the blocking material to air-seal the joist bay where a wall separates conditioned and unconditioned spaces.
    When using I-joists, make sure to fill in the gaps on each side of the blocking material to air-seal the joist bay where a wall separates conditioned and unconditioned spaces.
    When using I-joists, make sure to fill in the gaps on each side of the blocking material to air-seal the joist bay where a wall separates conditioned and unconditioned spaces.
    Figure 5. When using I-joists, make sure to fill in the gaps on each side of the blocking material to air-seal the joist bay where a wall separates conditioned and unconditioned spaces (Source: Courtesy of Steven Winter Associates).
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    Foam holes in open-web floor trusses to completely seal the rim joist
    Foam holes in open-web floor trusses to completely seal the rim joist
    Foam holes in open-web floor trusses to completely seal the rim joist
    Figure 6. Foam any holes in open-web floor trusses and caulk seams between boards to completely seal the rim joist (Source: Courtesy of Steven Winter Associates).
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    Use caulk or spray foam to air seal all four edges of the blocking material in each joist bay
    Use caulk or spray foam to air seal all four edges of the blocking material in each joist bay
    Use caulk or spray foam to air seal all four edges of the blocking material in each joist bay
    Figure 7. Use caulk or spray foam to air seal all four edges of the blocking material in each joist bay of a wall separating conditioned and unconditioned spaces (Source: Courtesy of Steven Winter Associates).
    1. Insulate the rim joist with additional rigid foam that is caulked or foamed into place or with spray foam. Use urethane spray foam insulation to cover the rim joist, and seams with the top plate below and subfloor above (see Figure 8). Medium-density (closed-cell, 2 pounds/cubic foot) or low-density (open-cell, 0.5 pounds/cubic foot) foams provide acceptable results. Open-cell foams might require additional vapor and condensation control measures in IECC Climate Zone 6 and higher. Have the spray foam installed by a spray foam subcontractor or use two-part spray foam kits. 

      Spray foam in band joists is typically concealed between floors so no other thermal barrier is required; however, the International Residential Code (IRC) allows the spray foam at rim joists to be exposed in basement and crawlspace applications (i.e., without a 15-minute thermal barrier such as drywall) as long as the thickness is less than 3 1/4 (3.25) inches and has a density range of 0.5 to 2.0 pounds per cubic foot (see 2021 IRC R316.5.11). Closed-cell, 2-PCF spray foams were approved in the 2003 IRC and open-cell 0.5-PCF foams were approved in the 2009 IRC, alongside any intermediate densities (BSC 2009).

      Climate Note: Although open-cell spray foam is acceptable in this application per code, closed-cell spray foam is preferred in hot-humid or extreme cold climates (IECC Climate Zones 1A, 2A, 7, and 8) (Zoeller 2009).
       

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    Spray foam insulates the rim joist and air seals the subfloor-rim joist and rim joist-top plate connections
    Spray foam insulates the rim joist and air seals the subfloor-rim joist and rim joist-top plate connections
    Spray foam insulates the rim joist and air seals the subfloor-rim joist and rim joist-top plate connections
    Figure 8. Spray foam insulates the rim joist and air-seals the subfloor-rim joist and rim joist-top plate connections (Source: Courtesy of Steven Winter Associates).
    1. Caulk or spray foam the garage slab-foundation wall junction. (See the guide Reduce Pest Intrusion for more on foundation sealing.)
    2. Seal all penetrations through the shared walls and ceilings. See the Building America Solution Center guides on Air Sealing Electrical Wiring and Air Sealing Piping and Plumbing

      Use gaskets, airtight drywall technique, etc., to make the common wall and ceiling airtight. Consider a “flash” seal approach - spray foam the entire ceiling and/or inter-zonal walls of the garage to air-seal any cracks, holes, or seams. Then add batt or blown insulation to meet the insulation R-value requirement (Figures 1 and 9), at a cost savings compared to using spray foam alone to meet the insulation requirement. Cover the ceiling insulation with taped and mudded drywall.

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    Garage ceiling with spray foam, flash air-seal, and batt insulation.
    Garage ceiling with spray foam, flash air-seal, and batt insulation.
    Garage ceiling with spray foam, flash air-seal, and batt insulation.
    Figure 9. Use a flash and batt approach to insulate and air-seal the garage ceiling (Source: Courtesy of Steven Winter Associates).
    1. Other Important Considerations:
      1. Install a self-closing, insulated, metal, fire-rated door with a good weather seal between the living space and the garage (see the BASC guide Air Sealing Doors Adjacent to Unconditioned Space).
      2. If the air handler for a central furnace must be located in the garage, it needs to be in an air-sealed closet (see the BASC guide No Ducts or Air Handlers Located in Garage and the report Air Sealing Mechanical Closets in Slab-On-Grade Homes). Do not have supply or return registers in the garage. If ductwork is located in the garage ceiling to service rooms above, verify that the ducts are air-sealed and insulated. Consider encapsulating the ducts with closed-cell spray polyurethane foam to ensure a complete air barrier (see the report Buried and/or Encapsulated Ducts).
      3. Install a passive vent from the garage to the outside. Consider installing a timer-operated exhaust fan that vents from the garage to the outside (see the guide Mechanical Ventilation for Attached Garage).
    Success
    Ensuring Success

    If the home has an attached garage, visually inspect for cracks or improper sealing along the rim joist above walls separating the garage from the home. For joist bays that extend from over the garage ceiling to over or under living areas of the house, the joist bay cavities should be blocked off, air sealed, and insulated. Rim joists that run parallel to the shared wall should be air sealed and insulated at the rim joist.

    Blower door testing conducted as part of the whole-house energy performance testing can indicate whether the rim joists have been successfully air sealed. Blower door testing can also help determine if the home is depressurized compared to the garage; if so, a means of supplying makeup air to the home may be called for to prevent garage fumes from being pulled into the home.

    The following actions are also recommended to ensure that garage air is separated from house air:

    • Visually inspect for cracks along the base of garage walls that adjoin living space and along sill plates on top of foundation walls on adjoining walls.
    • Visually inspect that all penetrations through adjoining walls and garage ceilings below living spaces are sealed.
    • Test the seal tightness of doors linking the garage with the rest of the home.
    • Best practice is to not install HVAC equipment in the garage. If a furnace is installed in the garage, it should be sealed combustion and direct vent. Visually inspect that the furnace cabinets and ducts are air sealed with mastic or metal tape or, preferably, that the furnace is installed in an air-sealed closet. No return air registers should be installed in the garage. Any ducts installed in the garage should be sealed with mastic and tested for air tightness.
    Climate
    Climate

    If the rim joists are to be sealed with spray foam both open-cell and closed-cell spray foam are acceptable, however, closed-cell spray foam is preferred in hot-humid or extreme cold climates (IECC Climate Zones 1A, 2A, 7, and 8) (Zoeller 2009).

    The map in Figure 1 shows the climate zones for states that have adopted energy codes equivalent to the International Energy Conservation Code (IECC) 2009, 12, 15, and 18. The map in Figure 2 shows the climate zones for states that have adopted energy codes equivalent to the IECC 2021. Climate zone-specific requirements specified in the IECC are shown in the Compliance Tab of this guide. 

     

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    IECC climate zone map
    IECC climate zone map
    IECC climate zone map
    Figure 1. Climate Zone Map from IECC 2009, 12, 15, and 18. (Source: 2012 IECC)
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    Climate Zone Map from IECC 2021
    Climate Zone Map from IECC 2021
    Climate Zone Map from IECC 2021
    Figure 2. Climate Zone Map from IECC 2021. (Source: 2021 IECC)
    Training
    Right and Wrong Images
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    Right - A “flash” seal approach with spray foam provides a continuous air barrier between the ceiling and walls of the garage and the living space.
    Right - A “flash” seal approach with spray foam provides a continuous air barrier between the ceiling and walls of the garage and the living space.
    Image
    Right - Air barrier is present between the garage and floor system.
    Right - Air barrier is present between the garage and floor system.
    Image
    Right - Air-sealing the wall between the garage and the home is vital for occupant health and safety.
    Right - Air-sealing the wall between the garage and the home is vital for occupant health and safety.
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    Right - All seams in the HVAC equipment and ductwork are sealed with mastic; because the HVAC equipment is in the garage, it is an air-sealed closet.
    Right - All seams in the HVAC equipment and ductwork are sealed with mastic; because the HVAC equipment is in the garage, it is an air-sealed closet.
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    Right – All wood-to-wood joints are air-sealed with caulk or tape.
    Right – All wood-to-wood joints are air-sealed with caulk or tape.
    Image
    Right – The band joist over this wall was properly insulated and air-sealed.
    Right – The band joist over this wall was properly insulated and air-sealed.
    Image
    Right – Closed-cell spray foam insulates and air-seals the rim joist above a shared wall between the garage and living space.
    Right – Closed-cell spray foam insulates and air-seals the rim joist above a shared wall between the garage and living space.
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    Right – Closed-cell spray foam insulation in the shared wall between the garage and living space helps to air-seal the wall and protect occupants from garage pollutants.
    Right – Closed-cell spray foam insulation in the shared wall between the garage and living space helps to air-seal the wall and protect occupants from garage pollutants.
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    Right – Every seam and nail hole in these garage-to-house walls is sealed with tape.
    Right – Every seam and nail hole in these garage-to-house walls is sealed with tape.
    Image
    Right - Penetrations through the band joist are properly air-sealed.
    Right - Penetrations through the band joist are properly air-sealed.
    Image
    Right - Sealant is installed at the top and bottom plates of a gypsum covered wall separating a garage from the conditioned space of the home.
    Right - Sealant is installed at the top and bottom plates of a gypsum covered wall separating a garage from the conditioned space of the home.
    Image
    Right – Spray foam insulates the walls and ceilings separating the garage from the home.
    Right – Spray foam insulates the walls and ceilings separating the garage from the home.
    Image
    Right - The ceiling above the garage is air-sealed and insulated with spray foam.
    Right - The ceiling above the garage is air-sealed and insulated with spray foam.
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    Right - The ceiling above the garage is insulated and air-sealed with open-cell spray foam to keep garage fumes out of the living space above.
    Right - The ceiling above the garage is insulated and air-sealed with open-cell spray foam to keep garage fumes out of the living space above.
    Image
    Wrong – An opportunity to use structural members as a natural air barrier was missed in this home and blocking was not initially planned for between the garage and living space.
    Wrong – An opportunity to use structural members as a natural air barrier was missed in this home and blocking was not initially planned for between the garage and living space.
    Image
    Wrong - The band joist above this garage-house shared wall is not properly sealed.
    Wrong - The band joist above this garage-house shared wall is not properly sealed.
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    Wrong - The rigid foam that was installed as an air barrier at the rim joist was not properly air-sealed.
    Wrong - The rigid foam that was installed as an air barrier at the rim joist was not properly air-sealed.
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    Wrong - No air barrier is present in the floor joists spanning over the garage and conditioned space of the home.
    Wrong - No air barrier is present in the floor joists spanning over the garage and conditioned space of the home.
    Image
    Wrong - No air barrier is present between the garage and floor system.
    Wrong - No air barrier is present between the garage and floor system.
    Image
    Wrong - The faced batt insulation does not provide an air barrier in the joist bay between the garage and the conditioned space of the home.
    Wrong - The faced batt insulation does not provide an air barrier in the joist bay between the garage and the conditioned space of the home.
    Image
    Wrong - Rigid insulation blocking is installed but not air-sealed with spray foam around edges.
    Wrong - Rigid insulation blocking is installed but not air-sealed with spray foam around edges.
    Image
    Wrong - The air barrier is not sealed (picture taken from garage looking into house).
    Wrong - The air barrier is not sealed (picture taken from garage looking into house).
    Image
    Wrong - When ceiling joists over a garage run perpendicular to the adjoining wall, the joist bays must be blocked and sealed to prevent garage fumes from entering the living space
    Wrong - When ceiling joists over a garage run perpendicular to the adjoining wall, the joist bays must be blocked and sealed to prevent garage fumes from entering the living space
    Image
    Gaps between garage and conditioned space are properly sealed by carefully cutting and then caulking wood sections to fit between trusses above shared walls.
    Gaps between garage and conditioned space are properly sealed by carefully cutting and then caulking wood sections to fit between trusses above shared walls.
    Image
    Plan view (from above) showing how the existing garage wall gypsum board is cut away to air-seal the shared wall before adding rigid foam insulation on the garage and exterior walls of the home.
    Plan view (from above) showing how the existing garage wall gypsum board is cut away to air-seal the shared wall before adding rigid foam insulation on the garage and exterior walls of the home.
    Image
    Plumbing penetrations through the subfloor are air-sealed.
    Plumbing penetrations through the subfloor are air-sealed.
    Image
    Rigid foam insulating sheathing is installed on existing garage ceiling and covered with a new gypsum board fire protection layer installed over the foam.
    Rigid foam insulating sheathing is installed on existing garage ceiling and covered with a new gypsum board fire protection layer installed over the foam.
    Image
    Rigid insulation and air-sealing can be used to thermally isolate garages from interior occupied space in multifamily row houses/townhouses.
    Rigid insulation and air-sealing can be used to thermally isolate garages from interior occupied space in multifamily row houses/townhouses.
    Image
    Rigid insulation and air-sealing can be used to thermally isolate garages from multifamily row houses/town houses with basement foundations in IECC Climate Zones 3 or higher.
    Rigid insulation and air-sealing can be used to thermally isolate garages from multifamily row houses/town houses with basement foundations in IECC Climate Zones 3 or higher.
    Image
    Side view showing air-sealing and rigid foam insulation is installed over existing wall and ceiling under a room above, then covered with new gypsum board.
    Side view showing air-sealing and rigid foam insulation is installed over existing wall and ceiling under a room above, then covered with new gypsum board.
    Image
    Side view showing how the existing garage wall and ceiling are air-sealed prior to installing rigid foam insulation on the garage side of the shared wall of an existing home.
    Side view showing how the existing garage wall and ceiling are air-sealed prior to installing rigid foam insulation on the garage side of the shared wall of an existing home.
    Image
    Spray foam insulation air-seals and insulates the floor above the garage; the joist will be filled with fibrous insulation in this flash-and-batt approach.
    Spray foam insulation air-seals and insulates the floor above the garage; the joist will be filled with fibrous insulation in this flash-and-batt approach.
    Image
    The original corner seam is air-sealed with caulk, then rigid foam is installed on the existing garage ceiling and walls, and finally covered with drywall.
    The original corner seam is air-sealed with caulk, then rigid foam is installed on the existing garage ceiling and walls, and finally covered with drywall.
    Image
    To ensure a complete air barrier between the garage and the house, the wall between the garage and the house was insulated and air-sealed with four inches of high-density spray foam.
    To ensure a complete air barrier between the garage and the house, the wall between the garage and the house was insulated and air-sealed with four inches of high-density spray foam.
    Presentations
    Videos
    Publication Date
    Author(s)
    Risinger
    Organization(s)
    Build with Matt Risinger
    Description
    Video describing examples of poor air sealing in a new home and good air sealing of the garage-to-house air barrier in a gut rehab.
    CAD
    CAD Files
    Air barrier at garage band joist - 1 inch rigid insulation with 1x3 wood furring
    Air barrier at garage band joist - 1 inch rigid insulation with 1x3 wood furring
    Download: DWG PDF
    Air barrier at garage band joist - 1 inch rigid insulation with 2x2 wood furring
    Air barrier at garage band joist - 1 inch rigid insulation with 2x2 wood furring
    Download: DWG PDF
    Air barrier at garage band joist - 1 1/2 inch rigid insulation with 2x4 sleepers
    Air barrier at garage band joist - 1 1/2 inch rigid insulation with 2x4 sleepers
    Download: DWG PDF
    Compliance

    Compliance

    The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

     

    ENERGY STAR Single-Family New Homes, Version 3/3.1 (Rev. 11)

    National Rater Field Checklist

    Thermal Enclosure System.
    2. Fully-Aligned Air Barriers 7 - At each insulated location below, a complete air barrier is provided that is fully aligned as follows:
    Ceilings: At interior or exterior horizontal surface of ceiling insulation in Climate Zones 1-3; at interior horizontal surface of ceiling insulation in Climate Zones 4-8. Also, at exterior vertical surface of ceiling insulation in all climate zones (e.g., using a wind baffle that extends to the full height of the insulation in every bay or a tabbed baffle in each bay with a soffit vent that prevents wind washing in adjacent bays). 8
    Walls: At exterior vertical surface of wall insulation in all climate zones; also at interior vertical surface of wall insulation in Climate Zones 4-8.9
    Floors: At exterior vertical surface of floor insulation in all climate zones and, if over unconditioned space, also at interior horizontal surface including supports to ensure alignment. Alternatives in Footnotes 12 & 13.11, 12, 13
    2.4 Walls adjoining porch roofs or garages.
    2.6 Floors above garages, floors above unconditioned basements or crawlspaces, and cantilevered floors.

    4. Air Sealing (Unless otherwise noted below, “sealed” indicates the use of caulk, foam, or equivalent material).
    4.7 Walls that separate attached garages from occupiable space sealed and, also, an air barrier installed and sealed at floor cavities aligned with these walls.
    4.9 Doors adjacent to unconditioned space (e.g., attics, garages, basements) or ambient conditions made substantially air-tight with weather-stripping or equivalent gasket.

    Footnote 7) For purposes of this Checklist, an air barrier is defined as any durable solid material that blocks air flow between conditioned space and unconditioned space, including necessary sealing to block excessive air flow at edges and seams and adequate support to resist positive and negative pressures without displacement or damage. EPA recommends, but does not require, rigid air barriers. Open-cell or closed-cell foam shall have a finished thickness ≥ 5.5 in. or 1.5 in., respectively, to qualify as an air barrier unless the manufacturer indicates otherwise. If flexible air barriers such as house wrap are used, they shall be fully sealed at all seams and edges and supported using fasteners with caps or heads ≥ 1 in. diameter unless otherwise indicated by the manufacturer. Flexible air barriers shall not be made of kraft paper, paper-based products, or other materials that are easily torn. If polyethylene is used, its thickness shall be ≥ 6 mil.

    Footnote 8) All insulated ceiling surfaces, regardless of slope (e.g., cathedral ceilings, tray ceilings, conditioned attic roof decks, flat ceilings, sloped ceilings), must meet the requirements for ceilings.

    Footnote 9) All insulated vertical surfaces are considered walls (e.g., above and below grade exterior walls, knee walls) and must meet the air barrier requirements for walls. The following exceptions apply: air barriers recommended, but not required, in adiabatic walls in multifamily dwellings; and, in Climate Zones 4 through 8, an air barrier at the interior vertical surface of insulation is recommended but not required in basement walls or crawlspace walls. For the purpose of these exceptions, a basement or crawlspace is a space for which ≥ 40% of the total gross wall area is below-grade.

    Footnote 11) EPA highly recommends, but does not require, an air barrier at the interior vertical surface of floor insulation in Climate Zones 4-8.

    Footnote 12) Examples of supports necessary for permanent contact include staves for batt insulation or netting for blown-in insulation. Alternatively, supports are not required if batts fill the full depth of the floor cavity, even when compression occurs due to excess insulation, as long as the R-value of the batts has been appropriately assessed based on manufacturer guidance and the only defect preventing the insulation from achieving the required installation grade is the compression caused by the excess insulation.

    Footnote 13) Alternatively, an air barrier is permitted to be installed at the exterior horizontal surface of the floor insulation if the insulation is installed in contact with this air barrier, the exterior vertical surfaces of the floor cavity are also insulated, and air barriers are included at the exterior vertical surfaces of this insulation.

    Please see the ENERGY STAR Single-Family New Homes Implementation Timeline for the program version and revision currently applicable in your state.

     

    DOE Zero Energy Ready Home (Revision 07)

    Exhibit 1 Mandatory Requirements.
    Exhibit 1, Item 1) Certified under the ENERGY STAR Qualified Homes Program or the ENERGY STAR Multifamily New Construction Program.
    Exhibit 1, Item 6) Certified under EPA Indoor airPLUS.

    Exhibit 2 DOE Zero Energy Ready Home Target Home.
    The U.S. Department of Energy’s Zero Energy Ready Home program allows builders to choose a prescriptive or performance path. The DOE Zero Energy Ready Home prescriptive path requires builders to meet or exceed the minimum HVAC efficiencies listed in Exhibit 2 of the National Program Requirements (Rev 07), as shown below. The DOE Zero Energy Ready Home performance path allows builders to select a custom combination of measures for each home that is equivalent in performance to the minimum HERS index of a modeled target home that meets the requirements of Exhibit 2 as well as the mandatory requirements of Zero Energy Ready Home Exhibit 1.

    Exhibit 2, Insulation and Infiltration) Whole house leakage must be tested and meet the following infiltration limits:

    • Zones 1-2: ≤ 3 ACH50;
    • Zones 3-4: ≤ 2.5 ACH50;
    • Zones 5-7: ≤ 2 ACH50;
    • Zone 8: ≤ 1.5 ACH50;
    • Attached dwellings: ≤ 3 ACH50.

    Footnote 23) Envelope leakage must be determined by an approved verifier using a RESNET-approved testing protocol.

     

    EPA Indoor airPLUS (Revision 04)

    4.3 Location of Air-Handling Equipment and Ductwork. The Indoor airPLUS checklist requires that builders not locate air handling equipment or ductwork in garages but notes that ducts and equipment may be located in building cavities adjacent to garage walls or ceilings if the cavities are separated from the garage space with a continuous air barrier.

    5.4 Attached Garages. The Indoor airPLUS checklist requires that garages are isolated from conditioned space. Builders must air-seal common walls and ceilings between attached garages and living spaces before installing insulation and use weather stripping or equivalent gasket to ensure all doors between living spaces and attached garages are substantially airtight. Indoor airPLUS also requires installation of an automatic door closer on all connecting doors between living spaces and attached garages.

    Homes with exhaust-only whole-house ventilation must be equipped with an exhaust fan vented directly outdoors (see the Indoor airPLUS Specifications for more information) or must have the builder verify that the garage-to-house air barrier can maintain a pressure difference of greater than 45 Pascals while the home maintains a 50 Pascal pressure difference with respect to the outdoors, with all doors and windows closed during the blower door test. 

     

    2009 International Energy Conservation Code (IECC)

    Table 402.4.2 Air Barrier and Insulation Inspection Component Criteria, Garage separation: Air sealing is installed between the garage and conditioned spaces. Table 402.4.2, Air barrier and thermal barrier: Exterior wall insulation is installed in substantial contact and continuous alignment with the air barrier. Air permeable insulation is not used as a sealing material.

    2012, 2015, and 2018 IECC

    Table R402.4.1.1 Air Barrier and Insulation Installation, Garage separation: Air sealing is installed between the garage and conditioned spaces. Table R402.4.1.1, General requirements: A continuous air barrier is installed in the building envelope including rim joists and exposed edges of insulation. Breaks or joints in the air barrier are sealed. Air permeable insulation is not used as a sealing material.

    2021 IECC

    Table R402.4.1.1 Air Barrier and Insulation Installation, Garage separation: Air sealing is installed between the garage and conditioned spaces. Insulated portions of the garage separation assembly shall be installed in accordance with sections R303 and R402.2.7.

    Retrofit:  2009, 2012, 2015, 2018,  and 2021 IECC

    Section R101.4.3 (in 2009 and 2012). Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with this code. (See code for additional requirements and exceptions.)

    Chapter 5 (in 2015, 2018, 2021). The provisions of this chapter shall control the alteration, repair, addition, and change of occupancy of existing buildings and structures.

     

    2009 International Residential Code (IRC)

    Table N1102.4.2 Air Barrier and Insulation Inspection Component Criteria, Garage separation: Air sealing is installed between the garage and conditioned spaces. Table N1102.4.2, Air barrier and thermal barrier: Exterior wall insulation is installed in substantial contact and continuous alignment with the air barrier. Air permeable insulation is not used as a sealing material.

    2012, 2015, and 2018 IRC

    Table N1102.4.1.1 Air Barrier and Insulation Installation, Garage separation: Air sealing is installed between the garage and conditioned spaces. Table N1102.4.1.1, General requirements: A continuous air barrier is installed in the building envelope including rim joists and exposed edges of insulation. Breaks or joints in the air barrier are sealed. Air permeable insulation is not used as a sealing material.

    2021 IRC

    Table N1102.4.1.1 Air Barrier and Insulation Installation, Garage separation: Air sealing is installed between the garage and conditioned spaces. Insulated portions of the garage separation assembly shall be installed in accordance with sections R303 and N1102.2.7.

    Retrofit:  2009, 2012, 2015, 2018,  and 2021 IRC

    Section R102.7.1 Additions, alterations, or repairs. Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with the requirements of this code, unless otherwise stated. (See code for additional requirements and exceptions.)

    Appendix J regulates the repair, renovation, alteration, and reconstruction of existing buildings and is intended to encourage their continued safe use.

     

    American Society for Testing Materials (ASTM) E1677-11

    Standard Specification for Air Barrier (AB) Material or System for Low-Rise Framed Building Walls. This specification covers minimum performances and specification criteria for an air barrier material or system for framed, opaque walls of low-rise buildings. The provisions are intended to allow the user to design the wall performance criteria and increase air barrier specifications for a particular climate location, function, or design.

     

    Air Barrier Association of America (ABAA) 07261

    Self-Adhered Sheet Air Barrier. 2006. Air Barrier Association of America, Walpole, MA. This specification for self-adhered sheet air barriers is developed by a professional association, the Air Barrier Association of America, to provide guidance to the design professional.

     

    ABAA 07262

    Fluid-Applied Air and Vapor Barrier. 2012. Air Barrier Association of America, Walpole, MA. This specification for air barriers that are fluid-applied and also act as vapor barriers is developed by a professional association, the Air Barrier Association of America, to provide guidance to the design professional.

     

    ABAA 07263

    Closed Cell, Medium-Density Spray Polyurethane Foam Air Barrier. 2011. Air Barrier Association of America, Walpole, MA. This specification for closed cell, medium-density spray polyurethane foam air barriers is developed by a professional association, the Air Barrier Association of America, to provide guidance to the design professional.

     

    ABAA 07265

    Fluid-Applied Vapor Permeable Air Barrier. 2012. Air Barrier Association of America, Walpole, MA. This specification for fluid-applied vapor permeable air barriers is developed by a professional association, the Air Barrier Association of America, to provide guidance to the design professional.

    Retrofit
    Existing Homes

    SCOPE

    Air-seal the walls and ceilings of a garage that is attached to an existing home’s conditioned space and living areas.

    • Determine which wall and ceiling assemblies in the garage are attached to the home’s living areas and inspect those assemblies for any cracks, holes, gaps, rot,  water damage, or deterioration.
    • Repair holes in ceilings or walls with sheet rock or plywood and seal to ensure a continuous air barrier.
    • Remove and replace any sheet rock that is rotten or has extensive water damage.
    • Use caulk or foam to seal any cracks or gaps. Sealants (e.g., caulk, fire-retardant caulk, fire-rated spray foam, etc.) should be compatible with all adjoining surfaces and meet the fire and air barrier specifications according to code.
    • Alterations that expose the existing framing cavity may require the installation of additional insulation. See the Compliance tab for alterations and repairs to existing walls.

    For more information on conditions that may be encountered when working with walls or ceilings in existing homes, see the pre-retrofit assessment guide on air sealing walls, windows, and doors.

    For more guidance on sealing walls, see the U.S. Department of Energy’s Standard Work Specifications (SWS) and follow safe work practices as described.

     

    DESCRIPTION

    The walls and ceilings separating the home from the garage may not have gotten the same attention to air sealing and insulating as the other exterior walls when the home was originally built because builders sometimes overlook the fact that these walls and ceilings are part of the home’s “building thermal envelope” (the exterior walls, floors, ceilings, and other building components that provide a boundary between conditioned space and the outdoors or unconditioned spaces).

    Maintaining the integrity of this thermal envelope, especially in regard to isolating the existing attached garage from living space is critical for preventing the potential infiltration of carbon monoxide and other contaminants into the dwelling. Over time, cracks or gaps may appear along the joints and seams in the sheet rock (gypsum board); at the mud sill, rim joists, subfloors, and bottom of the sheet rock; at ceiling-wall intersections; and at other areas where air can flow through if cracks or gaps are not adequately sealed. There could also be unsafe conditions that have existed since the house was built. For example, there could be open floor joist bays spanning from over the garage to over or beneath attached living space. These openings could allow garage fumes to enter adjoining rooms through cracks in subfloors or through leaks around sealing and wall penetrations. Any open joist bays must be closed off with solid blocking material and sealants as described in the Description tab.

    Any HVAC equipment installed in the garage should be installed in an airtight closet and there should be no supply or exhaust registers in the garage.

    In addition, certain changes to the home can cause the home to become depressurized, making it more likely for garage air to be drawn into the home if there are leaks in the air barrier between the home and the garage. Depressurization can occur when the house is airtight and an exhaust fan, range hood, clothes dryer, or combustion appliance is operated, if adequate makeup air is not provided to the house through a fresh air intake (a duct that brings outside air to the return side of the air handler). Changes to the house that could increase the likelihood of depressurization include adding a new higher powered range hood fan, adding or replacing exhaust fans, cleaning out the clothes dryer duct, air-sealing parts of the house, or adding a fireplace or other combustion appliance that does not have a sealed combustion chamber with a dedicated intake air duct.

    To help ensure that an airtight barrier separates the house from the garage, inspect the common walls between the home and the garage. The garage can also be tested for pressure differences with respect to the house using a blower door test. These steps can be done by a home energy rater as part of a home energy assessment.

    Also see the Solution Center guides Floor above Garage, Insulating Existing Floors over Garage, Garage Rim/Band Joist Adjoining Conditioned Space, Air Sealing Drywall to Top Plate, Air Sealing Doors Adjacent to Unconditioned Space, Air Sealing Attic Access Panels/Doors/Stairs, Rigid Foam Insulation Installed Between Existing House and Garage Walls, and No Ducts or Air Handlers Located in Garage.

     

    How to Air-Seal Between the Existing Garage and Living Space

    1. Locate and inspect the air barrier separating the garage from the conditioned space of the house at the home’s thermal envelope. Test for separation between the two using a blower door test. Air-seal all seams, any leaks around penetrations, and any joist bay cavities as described in the Description tab.
    2. Replace any materials that show signs of rot or water damage. To minimize crumbling of plaster when cutting through existing plaster and wood lathe surfaces, use high-speed cutting tools such as powered multi-tools or an angle grinder with a diamond blade, to make clean cuts through the plaster and lathe. Protect surfaces, hang tarps to isolate the area, and operate a shop vac to capture the dust. Another trick is to apply a sealing compound to the back side of the lathe, if it is accessible, prior to cutting to minimize flexing. Apply masking tape to the lines to be cut to help hold the lathe together. Wetting may also help reduce dust generation.
    3. Assume that paint on surfaces painted prior to 1978 contains lead. Old plaster may contain asbestos. See the assessment guide on hazardous materials and the EPA Healthy Indoor Environment Protocols for Home Energy Upgrades (2011) for more information.
    4. Check the door leading from the garage into the house. If the door is more than 15 years old, it may be a hollow door. A door between the garage and the home should be considered an exterior door. It should be either a solid core or insulated metal, fire-rated door. It should be weather-stripped, have a tight-fitting sweep, and have an automatic door-closing hinge. See the the guide Air Sealing Doors Adjacent to Unconditioned Space.

       

    COMPLIANCE

    See Compliance tab. 

    More

    More Info.

    Access to some references may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

    References and Resources*
    Author(s)
    Rudd Armin
    Organization(s)
    Building Science Corporation,
    BSC
    Publication Date
    Description
    This report describes research conducted to evaluate air transfer between the garage and living space in a single-family detached home constructed to the 2009 IECC by a production home builder in Maryland.
    Author(s)
    Air Infiltration and Ventilation Centre
    Organization(s)
    AIVC
    Publication Date
    Description
    Report describing information for builders and retrofitters about eliminating hazards and coincidental energy losses that come from attached garages.
    Author(s)
    Baechler Michael C,
    Gilbride Theresa L,
    Hefty Marye G,
    Cole Pam C,
    Love Pat M
    Organization(s)
    Pacific Northwest National Laboratory,
    PNNL,
    Oak Ridge National Laboratory,
    ORNL,
    U.S. Department of Energy,
    DOE
    Publication Date
    Description
    Guide describing measures that builders in the cold and very cold climates can take to build homes that have whole-house energy savings of 40% over the Building America benchmark with no added overall costs for consumers.
    Author(s)
    Zoeller William
    Organization(s)
    CARB,
    Steven Winter Associates,
    SWA
    Publication Date
    Description
    Document describing different spray foam materials including some pros and cons and technical specifications.
    *For non-dated media, such as websites, the date listed is the date accessed.
    Contributors to this Guide

    The following authors and organizations contributed to the content in this Guide.

    Sales
    Building Science Measures
    Building Science-to-Sales Translator

    Air Sealed Attached Garage =

    Image(s)
    Technical Description

    Air-sealed attached garages help block the leakage of carbon monoxide and other contaminants in the garage from getting into the home. This is achieved by blocking and air sealing floor framing cavities in ceilings above the garage that extend into living spaces; seams along the adjoining living space walls and foundation; and all seams and any holes between the ceiling and any living space above. In addition, any doors between the house and the garage should be self-closing and weather stripped, including a tight-fitting threshold sweep.


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