PNNL. 2012. Building America Case Study: David Weekley Homes, Eagle Springs & Waterhaven, Houston, TX. PNNL-SA-87333, prepared by the Pacific Northwest National Laboratory for the U.S. Department of Energy Building America Program.
Walls Behind Fireplaces
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Scope
Fully Aligned Air Barriers
- Install insulation without misalignments, compressions, gaps, or voids in all exterior wall cavities behind all fireplaces.
- Back with a fire-proof rigid air barrier or other supporting material to create a continuous thermal barrier and prevent a fire hazard.*
- Seal all seams, gaps, and holes of the air barrier with fire-rated caulk or foam before fireplace installation.
* ENERGY STAR recommends using a rigid air barrier, but it is not a requirement.
Notes:
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 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.
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Description
When a fireplace is installed on an exterior wall, it is important to install an air barrier behind it after installing insulation but before the fireplace is installed. 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. Air barrier material behind fireplaces must tolerate heat. Air barrier material can include thin sheet goods such as rigid insulation, sheet metal, or dry wall. These materials may be installed by insulators, framers, or subcontractors or vendors hired specifically to install the fireplace. This task should be included in the contract for the appropriate trade depending on the workflow at the specific job sites.
Note when designing the fireplace location, adequate clearance must be provided between the chimney and firebox and the insulation and air barrier material, as required by local codes and the manufacturer’s recommendations.
How to Insulate and Air Seal the Wall behind Your Fireplace
- Insulate the exterior wall enclosing the fireplace and chimney to the top of the second floor ceiling with rigid foam exterior sheathing taped at the seams and sealed at the edges.
- Install fire stop blocking.
- Install support blocking for thin-profile structural sheathing.
- Apply insulation (batt or spray foam) within the framing of the wall up to the ceiling or roof line.
- Install a thin structural sheathing material (e.g., drywall, rigid insulation, lightweight steel or aluminum sheeting). Bend the liner at the corners or seal seams with a bead of adhesive. Make
- Tape the liner to the enclosure opening on both the sides and at the top of the fireplace enclosure.
- Install the fireplace and chimney and closure framing.
- After the new fireplace insert and chimney are installed, seal the enclosure by placing a sheet-metal fire stop around the chimney pipe where it enters the firebox.
- Seal the joints and seams of the fire stop with an approved high-temperature sealant.
Figure 1 - Draft stopping and air barrier at fireplace enclosure, plan view 
Figure 2 - Draft stopping and air barrier at fireplace enclosure, side view
Ensuring Success
Air barrier effectiveness is measured at the whole-house level. High-performance branding programs and the IECC code require that builders meet specified infiltration rates at the whole-house level. See the “compliance” tab for these specified infiltration rates. Blower door testing may help indicate whether air leakage behind a fireplace has been successfully sealed. An infrared camera can be used in conjunction with the blower door testing to inspect the insulation and to detect air leakage behind the fireplace from the outside.
Climate
ENERGY STAR Version 3, (Rev. 6)
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.
International Energy Conservation Code (IECC) Climate Regions
Right and Wrong Images
Presentations
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Videos
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CAD Images
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SourceBuilding Plans for the ENERGY STAR Thermal Bypass Checklist
Green Building Advisor. 2011. Building Plans for the ENERGY STAR Thermal Bypass Checklist. Green Building Advisor, Newtown, Connecticut, The Tanton Press.
Organization:Green Building AdvisorSaveDownloadDownload PDFDownload PDF -
SourceBuilding Plans for the ENERGY STAR Thermal Bypass Checklist
Green Building Advisor. 2011. Building Plans for the ENERGY STAR Thermal Bypass Checklist. Green Building Advisor, Newtown, Connecticut, The Tanton Press.
Organization:Green Building AdvisorSaveDownloadDownload PDFDownload PDF
Compliance
ENERGY STAR Version 3, (Rev. 6)
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. Building envelope assemblies, including exterior walls and unvented attic assemblies (where used), shall comply with the relevant vapor retarder provisions of the 2012 International Residential Code.
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.
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.
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.
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.
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.
Table 402.4.2 Air Barrier and Insulation Inspection Component Criteria, Fireplace: Walls with fireplaces include air barriers.* 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.*
Table N1102.4.2 Air Barrier and Insulation Inspection Component Criteria, Fireplace: Walls with fireplaces include air barriers.* 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.*
Table R402.4.1.1 Air Barrier and Insulation Installation, Fireplace: Fireplace walls have air barrier and closure doors are gasketed.* 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.*
Table N1102.4.1.1 Air Barrier and Insulation Installation, Fireplace: Fireplace walls have air barrier and closure doors are gasketed.* 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.
References
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2009 IECC—International Energy Conservation Code
2009 IECC, International Energy Conservation Code. International Code Council, Washington, D.C.
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2009 IRC—International Residential Code for One and Two Family Dwellings
2009 IRC, International Residential Code for One and Two Family Dwellings. 2009. Fifth Printing. International Code Council, Washington, D.C.
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2012 IECC—International Energy Conservation Code
2012 IECC, International Energy Conservation Code. International Code Council, Washington, D.C.
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2012 IRC—International Residential Code for One and Two Family Dwellings
2012 IRC, International Residential Code for One and Two Family Dwellings. 2012. Second Printing. International Code Council, Washington, D.C.
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Air Barriers—Tub, Shower and Fireplace Enclosures, Information Sheet 407
Building Science Corporation. 2009. Air Barriers—Tub, Shower and Fireplace Enclosures. Information Sheet 407. Prepared by the Building Science Corporation for the Department of Energy's Building America Program.
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DOE Challenge Home National Program Requirements
DOE. 2012. DOE Challenge Home National Program Requirements (Rev. 02). Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy, Washington, D.C.
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ENERGY STAR Qualified Homes, Version 3 (Rev. 06) Inspection Checklist for National Program Requirements
EPA. 2012. ENERGY STAR Qualified Homes, Version 3 (Rev. 06) Inspection Checklist for National Program Requirements. U.S. Environmental Protection Agency, Washington, D.C.
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Thermal Enclosure System Rater Checklist Guidebook
EPA. 2011. Thermal Enclosure System Rater Checklist Guidebook. U.S. Environmental Protection Agency, Washington, D.C.
