Air Sealing Attached Garage


Last Updated: 12/12/2017

Scope

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

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, 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 Certified Homes, and Indoor airPLUS.

 

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 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. (Image courtesy of Steven Winter Associates)

Walls and floors adjoining garage 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 materials, such as caulk or spray foam. All joist cavities between the garage and adjoining living spaces should be blocked with rigid material 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. These same air-sealing concepts apply to overhangs and porch roofs.

To provide an air barrier between the garage and the adjoining conditioned space, solid blocking is often used to air seal joist bay openings spanning over the garage and conditioned space. A rigid material like rigid foam board, drywall, OSB, or plywood can be cut to fit each joist bay opening. Each piece must be cut to fit then nailed and caulked or spray foamed into place, which is a labor-intensive process.

The best option would be to design the home to isolate the attached garage through the use of framing members. 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. Where open bays would span the shared walls, the floor joists can be cut so that they terminate on either side of a rim joist installed over the shared wall. The joints between the mud sill and rim joist at the foundation line of the 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.

How to Air Seal between the Garage and Living Space

In all instances discussed below, air sealing of seams and cracks in framing with an appropriate, compatible sealant is required.

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.)

a. Design walls adjoining garages so that the rim joist board runs parallel to the common wall, providing a continuous natural air barrier.

b. Where ceiling joists run perpendicular to the adjoining wall (see Figure 2), 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).

c. 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 blocking to fill the irregular shape of the opening (Figure 6). Also seal holes in open-web floor trusses at the shared wall, if needed (Figure 7). Use caulk or spray foam to air seal all four edges in each bay (Figure 8). Make sure to completely air seal around the rigid air barrier to prevent moist air from reaching and condensing on the rim joist.

d. 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 9). 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. Foam can be applied 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 3.25 inches and has a density range of 0.5 to 2.0 pounds per cubic foot (see 2009 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, along with 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).

2. Caulk or spray foam the garage slab-foundation wall junction. (See the guide Reduce Pest Intrusion for more on foundation sealing.)

3. Seal all penetrations through the shared walls and ceilings. See the Building America Solution Center guides on air sealing electrical wiring and plumbing penetrations. Other guides are also available that cover other air sealing strategies. Use “Search” to find specific air sealing topics, such as ceilings, and others.

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 (Figure 10), at a cost savings compared to using spray foam alone to meet the insulation requirement. Cover the ceiling insulation with taped and mudded drywall.

4. Other Important Considerations:

a. Install a self-closing, insulated, metal, fire-rated door with a good weather seal between the living space and the garage.

b. 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 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, make sure it is encapsulated with closed-cell spray polyurethane foam to ensure a complete air barrier. (See the report Buried and/or Encapsulated Ducts.)

c. 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.

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
Figure 2. 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 courtesy of Steven Winter Associates)

 

A continuous rim joist separates the garage from the living space
Figure 3. A continuous rim joist separates the garage from the living space. 

 

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. (Image courtesy of Steven Winter Associates)

 

Insert rigid blocking pieces into each joist bay and fasten with caulk or nails
Figure 5. Insert rigid blocking pieces into each joist bay and fasten with caulk or nails. (Image courtesy of Steven Winter Associates)

 

When using I-joists, make sure to fill in the gaps on each side of the blocking material to air seal the joist bay
Figure 6. When using I-joists, make sure to fill in the gaps on each side of the blocking material to air seal the joist bay. (Image courtesy of Steven Winter Associates)

 

Foam holes in open-web floor trusses to completely seal the rim joist
Figure 7. Foam holes in open-web floor trusses to completely seal the rim joist. (Image courtesy of Steven Winter Associates)

 

Use caulk or spray foam to air seal all four edges of the blocking material in each joist bay
Figure 8. Use caulk or spray foam to air seal all four edges of the blocking material in each joist bay. (Image courtesy of Steven Winter Associates)

 

Spray foam insulates the rim joist and air seals the subfloor-rim joist and rim joist-top plate connections
Figure 9. Spray foam insulates the rim joist and air seals the subfloor-rim joist and rim joist-top plate connections. (Image courtesy of Steven Winter Associates)

 

Use a flash and batt approach to insulate and air seal the garage ceiling
Figure 10. Use a flash and batt approach to insulate and air seal the garage ceiling. (Image courtesy of Steven Winter Associates)

 

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

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

See the Compliance tab for more climate zone requirements.

IECC climate zone map
IECC climate zones

Training

CAD

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.

DOE Zero Energy Ready Home

 The U.S. Department of Energy (DOE) Zero Energy Ready Home program requires that builders comply with the U.S. Environmental Protection Agency (EPA) Indoor airPLUS program criteria. The Indoor airPLUS checklist (Item 4.3) 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. The Indoor airPLUS Construction Specifications (Item 5.4) requires that homes with exhaust-only whole-house ventilation either are equipped with an exhaust fan or that 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.

The DOE Zero Energy Ready Home Target Home Exhibit 2 specifies that homes be whole house leakage tested and meet the following infiltration limits: Zones 1-2: ≤ 3 ACH50; Zones 3-4: ≤ 2.5 ACH50; Zones 5-7: ≤ 2; Zone 8: ≤ 1.5. Envelope leakage must be determined by an approved verifier using a RESNET-approved testing protocol.

ENERGY STAR Certified Homes (Version 3, Rev. 08)

 The ENERGY STAR Certified Homes Rater Field Checklist requires (in Item 3m Fully Aligned Air Barriers) that a complete air barrier that is fully aligned with insulation be installed in at each insulated location of the home including: Ceilings: at the interior or exterior horizontal surface of ceiling insulation Climate Zones 1-3; at the interior horizontal surface of ceiling insulation in Climate Zones 4-8; at the exterior vertical surface of ceiling insulation in all climate zones; Walls: at the exterior vertical surface of wall insulation in all climate zones; also at the interior vertical surface of wall insulation in Climate Zones 4-8; Floors: at the exterior vertical surface of floor insulation in all climate zones and, if over unconditioned space, also at the interior horizontal surface including supports to ensure alignment. It specifically indicates several areas requiring a complete air barrier including Item 2.6 floors above garages and Item 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.

Rater Design Checklist Footnote: (6) Where an insulated wall separates a garage, patio, porch, or other unconditioned space from the conditioned space of the house, slab insulation shall also be installed at this interface to provide a thermal break between the conditioned and unconditioned slab. Where specific details cannot meet this requirement, partners shall provide the detail to EPA to request an exemption prior to the home’s certification. EPA will compile exempted details and work with industry to develop feasible details for use in future revisions to the program. A list of currently exempted details is available at: energystar.gov/slabedge.

Rater Field Checklist Footnotes:

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.

6. 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.

7. 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.

8. Exterior air barriers are not required for attic knee walls that are ≤ 24 in. in height if an interior air barrier is provided and insulation extends in all directions from the top of this interior air barrier into unconditioned space at the following levels: CZ 1-5: ≥ R-21; CZ 6-8: ≥ R-30.

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

10. 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.

11. 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.

12. The minimum designated R-values must be achieved regardless of the trade-offs determined using an equivalent U-factor or UA alternative calculation, ...

13. Where an insulated wall separates a garage, patio, porch, or other unconditioned space from the conditioned space of the house, slab insulation shall also be installed at this interface to provide a thermal break between the conditioned and unconditioned slab. Where specific details cannot meet this requirement, partners shall provide the detail to EPA to request an exemption prior to the home’s certification. EPA will compile exempted details and work with industry to develop feasible details for use in future revisions to the program. A list of currently exempted details is available at: energystar.gov/slabedge.

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.

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.

2009 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.

Retrofit: 2009, 2012, 2015, and 2018 IECC

Section R101.4.3 (Section R501.1.1 in 2015 and 2018 IECC). 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.)

2009 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.

Retrofit: 2009, 2012, 2015, and 2018 IRC

Section N1101.3 (Section N1107.1.1 in 2015 and 2018 IRC). 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.)

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

Air Sealing and Insulating Garage Walls - Code Compliance Brief

Overview: 

The intent of this brief is to provide code-specific information about air sealing and insulating garage walls to help ensure that the measure will be accepted as being in compliance with the code. Providing notes for code officials on how to plan reviews and conduct field inspections can help builders or remodelers with proposed designs and installations and provide jurisdictional officials with information for acceptance. Providing the same information to all interested parties (e.g., code officials, builders, designers, etc.) is expected to result in increased compliance and fewer innovations being questioned at the time of plan review and/or field inspection.

As in other parts of the home, sealing and insulating the walls and ceiling of your garage can be an effective way to improve energy efficiency in a home. In addition, properly isolating and air sealing attached garages from the living space is critical for preventing the potential infiltration of carbon monoxide and other contaminants into the home. Open joist bays above the garage that extend into living spaces need to be blocked and air sealed at the garage wall. Seams along the rim joist, top plate, sill plate, and foundation wall should be caulked or sealed. If there is living space above the garage, extra care should be taken to seal all seams and any holes in the subfloor, and any doors between the house and the garage should be weather stripped and have a tight-fitting threshold sweep.

Insulation and air-sealing requirements for garage walls shared with conditioned space are found in the International Energy Conservation Code (IECC) and International Residential Code (IRC). Even though each version of the 2009, 2012, and 2015 IECC/IRC codes has included provisions that the building thermal envelope1 should be durably sealed to limit infiltration, the language related to air barriers and insulation in the 2009 version was somewhat vague and did not specify specific components of the building thermal envelope. The 2012 IECC/IRC added more specific language regarding areas of the building thermal envelope that should be sealed and expanded upon those areas that are now included in the 2015 IECC/IRC as well. This brief provides an overview of the 2009 through 2015 IRC/IECC code requirements related to air sealing and insulating attached garage walls.

 


1"Building Thermal Envelope" is defined as the basement walls, exterior walls, floor, roof, and any other building elements that enclose conditioned space or provide a boundary between conditioned space and exempt or unconditioned space.

Plan Review: 

Per the IECC/IRC, Section R103.3/R106.3 Examination of documents. The code official/building official must examine or cause to be examined construction documents for code compliance.

This section lists applicable code requirements and details helpful for plan review regarding the provisions to meet the requirement for insulated and air sealed attached garage walls.

  • Construction Documentation. Review the construction documents for details describing garage wall insulation, installation and construction techniques.
    • 2015 IECC/IRC, Section R103.2/N1101.5 Information on Construction Documents. Construction documents should include:
      • insulation materials and their R-values
      • manufacturer specifications on garage door leading into conditioned space including rated and labeled U-factor
      • air sealing details
  • Air Leakage and Insulation. Review the construction documents and confirm that the insulation material, R-value, and air-sealing technique meet applicable code requirements.
    • 2015 IECC/IRC, R402.4./N1102.4. Air Leakage. The building thermal envelope should be constructed to limit air leakage.
    • R402.4.1/N1102.4.1 Building Thermal Envelope. The sealing methods between dissimilar materials should allow for differential expansion and contraction.
    • R402.4.1.1/N1102.4.1.1 Installation. The components listed in the Air Barrier and Insulation Installation Table2 should be installed in accordance with the manufacturer’s instructions and the criteria listed as the applicable method of construction. Below are the General Requirements and components from the table that are applicable to sealing and insulating attached garage walls.
    • R402.4.1.1/N1102.4.1.1 Air Barrier and Insulation Installation Table
      • Air Barrier General Requirements. A continuous air barrier3 should be installed in the building envelope. The exterior thermal envelope contains a continuous air barrier. Breaks or joints in the air barrier4 should be sealed.
      • Air Barrier Criteria:
        • Walls – The junction of the foundation and sill plate should be sealed. The junction of the top plate and top of exterior walls should be sealed.
        • Floors (including above garages) – The air barrier should be installed at any exposed edge of insulation.
        • Garage separation – Air sealing should be provided between the garage and conditioned space.
      • Insulation Installation:
        • Walls – Cavities within corners and headers of frame walls should be insulated by completely filling the cavity with a material having a thermal resistance of R-3 per inch minimum. Exterior thermal envelope insulation for framed walls should be installed in substantial contact and continuous alignment with the air barrier.
        • Floors (including above garages) – Floor framing cavity insulation should be installed to maintain permanent contact with the underside of subfloor decking, or floor framing cavity insulation should be permitted to be in contact with the top side of sheathing, or continuous insulation installed on the underside of the floor framing and extends from the bottom to the top of all perimeter floor framing members.
        • Narrow cavities – Batts in narrow cavities should be cut to fit, or narrow cavities should be filled by insulation that on installation readily conforms to the available cavity space.
    • 2012 IECC/IRC, R402.4/N1102.4 Air Leakage. The building thermal envelope should be constructed to limit air leakage.
      • R402.4.1/N1102.4.1 Building Thermal Envelope. The sealing methods between dissimilar materials should allow for differential expansion and contraction.
      • R402.4.1.1/N1102.4.1.1 Installation. The components listed in the Air Barrier and Insulation Installation Table should be installed in accordance with the manufacturer’s instructions and the criteria listed as the applicable method of construction. Below are the components from the table that are applicable to sealing and insulating attached garage walls.
      • R402.4.1.1/N1102.4.1.1 Air Barrier and Insulation Installation Table
        • Walls – Corners and headers should be insulated and the junction of the foundation and sill plate should be sealed. The junction of the top plate and top of exterior walls should be sealed. Exterior thermal envelope insulation for framed walls should be installed in substantial contact and continuous alignment with the air barrier.
        • Garage Separation – Air sealing should be provided between the garage and conditioned spaces.
        • Floors (including above-garage floors) – Insulation should be installed to maintain permanent contact with underside of subfloor decking. The air barrier should be installed at any exposed edge of insulation.
        • Narrow Cavities – Batts in narrow cavities should be cut to fit, or narrow cavities should be filled by insulation that on installation readily conforms to the available cavity space.
    • 2009 IECC/IRC, 402.4.1 Air leakage, Building Thermal Envelope
      • The building thermal envelope should be constructed to limit air leakage. The sealing methods between dissimilar materials should allow for differential expansion and contraction. Sources of infiltration should be caulked, gasketed, weather stripped, or otherwise sealed with an air barrier material, suitable film, or solid material:
        • All joints, seams, and penetrations
        • Site-built windows, doors and skylights
        • Openings between window and door assemblies and their respective jambs and framing
        • Utility penetrations
        • Walls and ceilings separating a garage from conditioned spaces
        • Rim joist junction
        • Other sources of infiltration.

 


2Table R402.4.1.1 of the IECC and Table N1102.4.1.1 of the IRC.

3"Continuous air barrier" is defined as a combination of materials and assemblies that restrict or prevent the passage of air through the building thermal envelope.

4"Air Barrier" is defined as material(s) assembled and joined together to provide a barrier to air leakage through the building thermal envelope. An air barrier may be a single material or a combination of materials.

EXISTING BUILDINGS

Since the most recent edition of the 2015 IECC/IRC regarding existing buildings was restructured and includes new language regarding additions, alterations, and repairs, the following provisions are for the 2015 code versions only.

Review the construction documents and confirm whether compliance is required based on the scope of work proposed on the existing building:

  • Work proposed is exempt (not required) to meet the provisions of the code
  • Work proposed is not exempt and proper documentation has been submitted that specifies compliance will be met.

2015 IECC/IRC, Section R501.1.1/N1107.1.1 Additions, alterations, or repairs: General. Additions, alterations, or repairs to an existing building, building system or portion thereof should comply with Section R502/N1108, R503/N1109 or R504/N1110. Unaltered portions of the existing building or building supply system are not required to comply.

  • ADDITIONS - Building additions that include an attached garage are subject to the air-sealing and insulation requirements listed in the IECC/IRC.
    • R502.1/N1108.1 General. Additions to existing buildings should conform to code as they relate to new construction without requiring the unaltered portion of the existing building or building system to comply.
    • R502.1.1.1/N1108.1.1.1 Building Envelope. New building envelope assemblies that are part of the addition should comply with Sections R402l1/N1102.1, R402.2/N1102.2, R402.3.1/N1102.3.1 through R402.3.3.5/N1102.3.5 and R402.4/N1102.4

      Exception: where non-conditioned space is changed to conditioned space, the building envelope of the addition must comply where the UA (U-factor x Area), as determined in Section R402.1.4/N1102.1.4 (U-factor Alternative), of the existing building and the addition, and any alterations that are part of the project is less than or equal to UA generated for the existing building.

      Note: showing compliance with this exception is very difficult in that the builder must know what the existing insulation and fenestration ratings are and typically documentation for the fenestration is no longer available and assumptions would have to be made as to the insulation R-value installed in existing framed and sealed walls.

  • ALTERATIONS
    • R503.1/N1109.1 General. Alterations to any building or structure must comply with the requirements of the code as new construction. Alterations should be such that the existing building or structure uses no more energy than the existing building or structure prior to the alteration.
    • R503.1.1/N1109.1.1 Building Envelope. Building envelope assemblies that are part of the alteration must comply with Sections R402.1.2/N1102.1.2 (Insulation and Fenestration Table) or R402.1.4/N1102.1.4 (U-factor Alternative), and Section R402.2.1/N1102.2.1 through R402.2.12/N1102.2.12, R402.3/1/N1102.3.1, R402.3.2/N1102.3.2, R402.4.3/N1102.4.3 and R402.4.4/N1102.4.4

      Exception: The following alterations need not comply with the requirements for new construction provided the energy use of the building is not increased:

      • Existing wall cavities exposed during construction, provided that the cavities are filled with insulation
      • Construction where the existing wall cavity is not exposed
Field Inspection: 

Per the 2015 IECC, Section R104, Inspections, construction, or work for which a permit is required is subject to inspection. Construction or work is to remain accessible and exposed for inspection purposes until approved. Required inspections include footing and foundation, framing and rough-in work, plumbing rough-in, mechanical rough-in, and final inspection.

Per the 2015 IRC, Section R109, Inspections. The wording is somewhat different in that for onsite construction, from time to time the building official, upon notification from the permit holder or his agent, can make or cause to be made any necessary inspections. Further details are provided for inspections regarding foundation, plumbing, mechanical, gas and electrical, floodplain, frame and masonry, and final inspection. Any additional inspections are at the discretion of the building official.

This section provides details for inspecting to the specific provisions for insulating and sealing garage walls where one or more specific type of inspection per the IECC or IRC may be necessary to confirm compliance. Verifying code compliance for insulating and sealing garage walls would typically be at the framing and rough-in work inspection.

Technical Validation(s): 

This section provides additional information and helpful resources.

More Info.

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Case Studies

None Available

References and Resources*

  1. Author(s): International Code Council
    Organization(s): ICC
    Publication Date: January, 2009

    Code establishing a baseline for energy efficiency by setting performance standards for the building envelope (defined as the boundary that separates heated/cooled air from unconditioned, outside air), mechanical systems, lighting systems and service water heating systems in homes and commercial businesses.

  2. Author(s): International Code Council
    Organization(s): ICC
    Publication Date: January, 2009

    Code for residential buildings that creates minimum regulations for one- and two-family dwellings of three stories or less. It brings together all building, plumbing, mechanical, fuel gas, energy and electrical provisions for one- and two-family residences.

  3. Author(s): International Code Council
    Organization(s): ICC
    Publication Date: January, 2012

    Code establishing a baseline for energy efficiency by setting performance standards for the building envelope (defined as the boundary that separates heated/cooled air from unconditioned, outside air), mechanical systems, lighting systems and service water heating systems in homes and commercial businesses.

  4. Author(s): International Code Council
    Organization(s): ICC
    Publication Date: January, 2012

    Code for residential buildings that creates minimum regulations for one- and two-family dwellings of three stories or less. It brings together all building, plumbing, mechanical, fuel gas, energy and electrical provisions for one- and two-family residences.

  5. Author(s): Baechler, Gilbride, Hefty, Cole, Love
    Organization(s): Pacific Northwest National Laboratory, Oak Ridge National Laboratory
    Publication Date: February, 2011

    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.

  6. Author(s): Building Science Corporation
    Organization(s): Building Science Corporation
    Publication Date: September, 2009

    Information sheet about air sealing.

  7. Author(s): Department of Energy
    Organization(s): DOE
    Publication Date: April, 2017

    Standard requirements for DOE's Zero Energy Ready Home national program certification.

  8. Author(s): Aspen Publishers
    Organization(s): Aspen Publishers
    Publication Date: January, 2000
    Report with information for builders and retrofitters to help eliminate hazards and coincidental energy losses that come from attached garages.
  9. Author(s): Zoeller
    Organization(s): CARB, Steven Winter Associates, SWA
    Publication Date: April, 2009

    Information sheet about insulation materials.

Contributors to this Guide

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

Steven Winter Associates, lead for the Consortium for Advanced Residential Buildings (CARB), a DOE Building America Research Team