Garage Rim/Band Joist Adjoining Conditioned Space

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Climate

ENERGY STAR Version 3, (Rev. 07)

Thermal Enclosure Checklist, Fully-Aligned Air Barriers. A complete air barrier shall be provided that is fully aligned with the insulation at exterior surface of walls in all climate zones; and also at interior surface of walls for Climate Zones 4-8.

DOE Challenge Home

Exhibit 2: DOE Challenge Home Target Home. Infiltration (ACH50): Zones 1-2: 3; Zones 3-4: 2.5; Zones 5-7: 2; Zone 8: 1.5. Envelope leakage shall be determined by an approved verifier using a RESNET-approved testing protocol.

climate zone map

International Energy Conservation Code (IECC) Climate Regions

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Description

Attached garages can be a significant source of indoor air pollutants. Fumes from cleaning chemicals, garden fertilizers, pesticides, and vehicle exhaust are among the many contaminants that can be drawn into homes from attached garages if the walls and doors between the home and the garage aren’t adequately air sealed. Open joist bays above the garage that extend into living spaces are one air pathway. Air flow through 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. 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).

For occupant health and safety, consider designing homes with detached garages. If attached, the garage should be completely air sealed from the living areas of the house with rigid foam, spray foam, and/or caulk. When garage ceiling joists span both the living space and the garage, the joist bay cavities must be blocked off and sealed. It is preferable to design the garage so that rim joists run parallel with the adjoining wall to act as a natural air barrier. The rim joists should be insulated and all seams where components (including the rim joist, top plate, and subfloor) come together should be sealed with caulk or spray foam. Seams between the bottom plate and the slab of the adjoining wall should also be caulked or foamed. This air sealing could be done by the framer or the insulation installer. This task should be included in the contract for the appropriate trade depending on the workflow at the specific job site.

If the air handler for a central furnace must be located in the garage, it should be in an air-sealed closet with a dedicated air intake for combustion, a flue that exhausts to the outside, and a fresh-air intake ducted from the outside to the return side of the plenum so that it is not drawing garage air to circulate through the house. Determine whether a garage exhaust fan is advisable. Do not have supply or return registers in the garage.

Install carbon monoxide detectors inside the home.

How to Air Seal the Rim Joist between the garage and living space using rigid foam


1. Design walls adjoining garages so that the rim joist board runs parallel to the wall, providing a continuous natural air break. Where ceiling joists run perpendicular to the adjoining wall, one option is to make the rim joist continuous and have separate but aligned ceiling joists on each side of the rim joist.

A continuous rim joist separates the garage and living space

Figure 1 - A continuous rim joist separates the garage and living space  Reference

2. Cut a rectangle of rigid foam (polyisocyanurate or extruded polystyrene) to fit into each floor joist bay cavity. If the joist bay is open, make a backstop for the foam by tacking furring strips to the joists in line with the foundation or house wall. If the joist area is closed, caulk all seams.

Garage wall rim joist open to area between or under floors of living space  

Figure 2 - Garage wall rim joist open to area between or under floors of living space  Reference

3. Insert rigid foam pieces into each joist bays and fasten with caulk or nails.

Fitting rigid foam in garage wall rim joist cavities 

Figure 3 - Fitting rigid foam in garage wall rim joist cavities  Reference

4. Use caulk or spray foam to air seal all four edges in each bay. Make sure to completely air seal around the rigid foam to prevent moist air from reaching and condensing on the rim joist.

Caulk around each piece of rigid foam in garage wall rim joist cavities 

Figure 4 - Caulk around each piece of rigid foam in garage wall rim joist cavities  Reference

5. Add additional layer or rigid foam or batt insulation to meet or exceed the code-required insulation level for an exterior wall.

How to Air Seal the Rim Joist between the garage and living space using spray foam


1. Use urethane spray foam insulation to cover the rim joist, top plate, and subfloor above. High 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 by the use of 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 3-¼ inch (see 2009 IRC R314.5.11).  High-density (closed-cell, 2-PCF) spray foams were approved in the 2003 IRC, and low-density (open-cell, 0.5-PCF) foams were approved in the 2009 IRC, as well as any intermediate densities (BSC 2009).

Climate Note: Although open-cell spray foam is 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) (CARB 2009).

Spray foam insulates the rim joist and air seals the subfloor-rim joist and rim joist-top plate connections 

Figure 5 - Spray foam insulates the rim joist and air seals the subfloor-rim joist and rim joist-top plate connections  Reference

2. For additional protection when living space is located above the garage, consider a “flash” seal approach - spray foam the entire ceiling of the garage to air seal any cracks, holes, or seams in the subfloor. Then add batt insulation to meet the insulation R-value requirement and save cost compared to filling joists to the required thickness with spray foam alone. Cover the ceiling insulation with taped and mudded drywall.

Garage ceiling with spray foam flash air seal plus batt insulation 

Figure 6 - Garage ceiling with spray foam flash air seal plus batt insulation  Reference

Other Considerations

  1. Seal all penetrations through the common wall and ceiling. Use gaskets, airtight drywall technique, etc., to make the common wall and ceiling airtight. Caulk or spray foam garage slab-foundation wall junction.
  2. Install a self-closing, insulated, metal, fire-rated door with a good weather seal between the living space and the garage.
  3. Install a passive roof vent to keep the garage at a negative pressure in relationship to the house or consider installing a timer-operated exhaust fan that vents to the outside.
  4. If central HVAV is installed in the garage, install a closed-combustion unit that draws intake combustion air from outside, vents exhaust air to outside, and has a fresh air intake ducted to the outside. Install unit in an air-sealed closet. Mastic seal any ducts located in the garage. Do not install any return registers in the garage. 

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 may help indicate whether the rim joists have been successfully air sealed. With the home depressurized, check for air leaks at the rim joist with a smoke pencil or by feeling with the hand. Blower door testing can also help determine if the home is depressurized compared to the outside; if so, additional ventilation may be called for to prevent garage fumes from being pulled into the home. An infrared camera may also be used to determine air leakage between the garage and the house, if a sufficient temperature difference exists between the garage and the conditioned space of the house to see the leakage.

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. Visually inspect that furnaces installed in the garage have cabinets and ducts that are air sealed with mastic or metal tape or, preferably, that furnaces are 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.

Scope

Garage rim/band joist adjoining conditioned space

Fully Aligned Air Barriers

  1. Install a continuous rigid air barrier or other supporting material to separate the garage from the conditioned space.
  2. Seal all seams, gaps, and holes of the air barrier with caulk or foam and complete before installing the insulation.
  3. Install insulation without misalignments, compressions, gaps, or voids in all band joist cavities.

ENERGY STAR Notes:

ENERGY STAR highly recommends using a rigid air barrier, but it is not a requirement.

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. ENERGY STAR recommends, but does not require, rigid air barriers.  Open-cell or closed-cell foam shall have a finished thickness >= 5.5 inches or 1.5 inches, 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 inch 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.

ENERGY STAR highly recommends, but does not require, inclusion of an interior air barrier at band joists in Climate Zone 4 through 8.

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, with the exception of adiabatic walls in multifamily dwellings. 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.

Training

Right and Wrong Images

Presentations

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Compliance

ENERGY STAR Version 3, (Rev. 07)

Thermal Enclosure Checklist, Fully-Aligned Air Barriers. A complete air barrier shall be provided that is fully aligned with the insulation at exterior surface of walls in all climate zones; and also at interior surface of walls for Climate Zones 4-8. 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, with the exception of adiabatic walls in multifamily dwellings.
      
DOE Challenge Home

Exhibit 2: DOE Challenge Home Target Home. Certified under ENERGY STAR Qualified Homes Version 3. Infiltration (ACH50): Zones 1-2: 3; Zones 3-4: 2.5; Zones 5-7: 2; Zone 8: 1.5. Envelope leakage shall be determined by an approved verifier using a RESNET-approved testing protocol.
      
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.*

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 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, Air barrier and thermal barrier: 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.*

2012 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, Air barrier and thermal barrier: 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.*

*Due to copyright restrictions, exact code text is not provided.  For specific code text, refer to the applicable code.      

More Info.

Case Studies

  1. Author(s): PNNL
    Organization(s): PNNL
    Publication Date: April 2012

    Case study about design and testing 10 high-performance homes in Farmington, Connecticut.

References and Resources*

  1. Author(s): Baechler, Gilbride, Hefty, Cole, Love
    Organization(s): PNNL, ORNL
    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.

  2. Author(s): BSC
    Organization(s): BSC
    Publication Date: September 2009

    Information sheet about air sealing.

  3. Author(s): DOE
    Organization(s): DOE
    Publication Date: June 2013

    Standard requirements for DOE's Challenge Home national program certification.

  4. Author(s): EPA
    Organization(s): EPA
    Publication Date: June 2013

    Standard document containing the rater checklists and national program requirements for ENERGY STAR Certified Homes, Version 3 (Rev. 7).

  5. 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.

  6. Author(s): EPA
    Organization(s): EPA
    Publication Date: October 2011

    Guide describing details that serve as a visual reference for each of the line items in the Thermal Enclosure System Rater Checklist.

  7. Author(s): Zoeller
    Organization(s): CARB
    Publication Date: April 2009

    Information sheet about insulation materials.

Last Updated: 08/15/2013

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