Air Sealing Electrical Wiring

    Scope Images
    Image
    Air seal around all wiring installed through walls, ceilings, and flooring to keep conditioned air from leaking into unconditioned space.
    Scope

    Air seal around all electrical wiring and electrical boxes installed through walls, ceilings, and flooring to prevent air leakage and moisture movement between unconditioned and conditioned space. 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.

    • Using a drill, cleanly cut holes for electrical wiring no more than 1 inch larger in diameter than the wiring diameter.
    • Seal around installed wiring using caulk or canned spray foam. 
    • For ceiling-mounted electrical boxes, install the electrical box in the ceiling drywall, then caulk around the base and caulk all holes in the box with fire-retardant caulk.
    • For wall-mounted electrical boxes, install gasketed, airtight electrical boxes or install standard electrical boxes, then caulk all openings and seal the box to the drywall with caulk.

    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

    Air can pass through tiny gaps around electrical wiring and holes in electrical boxes, carrying conditioned air into wall cavities and up into unconditioned attics or allowing air from unconditioned garages and crawlspaces into living spaces. Pressure and temperature differences between conditioned and unconditioned spaces encourage this air flow. These air leaks represent energy losses, and they could also potentially allow warm, moisture-laden air into unconditioned spaces where it can condense on cold surfaces creating moisture problems. Conversely, air leaking into the house from the garage or crawlspace can affect indoor air quality and cause drafts. Air barriers need to be continuous to be effective; this means sealing all penetrations in exterior walls and in walls, ceilings, or floors adjoining unconditioned spaces. Holes drilled through studs and top and bottom plates should be caulked or foam sealed to prevent air from following the wiring through wall cavities.

    Be sure to schedule caulking of electrical penetrations after the wiring has been installed and before the drywall is completed. Responsibility for sealing air leaks around electrical wiring and electrical boxes should be included in the contract for the appropriate trade, depending on the workflow at specific job sites.

    How to Air Seal Electrical Boxes and Wiring

    • For ceiling-mounted electrical boxes, install the electrical box in the ceiling drywall, then caulk around the base and caulk all holes in the box with fire-retardant caulk.
      Caulk electrical boxes mounted in the ceiling.
      Figure 1. Air seal electrical box with fire-retardant material (Source: Courtesy of PNNL). 
    • For wall-mounted electrical boxes, specify that the electrician install prefabricated, airtight electric boxes that have flexible boot seals at wire penetrations and a gasketed flange at the face.
      Air-tight electrical boxes have built-in gaskets and self-sealing wire holes.
      Figure 2. Air sealing an electrical box (Source: Air Barriers - Airtight Drywall Approach, Info-401 2009). 
    • Or, as another option, install standard electrical boxes and caulk all of the openings in the box (including around wire penetrations), then seal the face of the box to the drywall with caulk.
      Caulk holes in the electrical box, caulk the wire holes, and caulk the face of the box to the drywall.
      Figure 3. Air sealing a plastic electrical box (Source: Air Barriers - Airtight Drywall Approach, Info-401 2009). 
    • Seal all wiring holes through the exterior walls of the house, such as holes for electrical wiring, security system wiring, television and telephone cables, porch light fixtures, and exterior electrical outlets. Use caulk, gaskets, or spray foam (note that spray foam degrades in sunlight).
      Air seal the electrical panel.
      Figure 4. Air sealing wiring holes (Source: Air Barriers - Airtight Drywall Approach, Info-401 2009). 
    • Use caulk or canned spray foam to seal wiring holes through all top plates and bottom plates.
      Foam wiring holes in top plate.
      Figure 5. Air sealing wiring holes with foam (Source: Building America Best Practices Series Volume 12: 40% Whole-House Energy Savings in the Cold and Very Cold Climates 2011). 
    Ensuring Success

    Holes around wiring should be visually checked to see if caulk and canned spray foam have been applied before insulation and drywall are installed. Blower door testing, which is conducted as part of the whole-house energy performance test-out, may help indicate whether holes for electrical wiring in exterior walls have been successfully sealed. An experienced technician can also check for air leaks with a smoke pencil or by feeling with the back of the hand.

    Climate

    No climate-specific information applies.

    Right and Wrong Images
    Image
    Wrong – Holes have been cut larger than needed, making it difficult to seal
    Wrong – Holes have been cut larger than needed, making it difficult to seal
    Image
    Right – Wiring penetrations have been neatly sealed with foam
    Right – Wiring penetrations have been neatly sealed with foam
    Image
    Wrong – Hole was not neatly cut with a saw, making it difficult to seal
    Wrong – Hole was not neatly cut with a saw, making it difficult to seal
    Image
    Right – Wiring penetrations have been neatly sealed with foam
    Right – Wiring penetrations have been neatly sealed with foam
    Image
    Wrong – Hole has not been air sealed
    Wrong – Hole has not been air sealed
    Image
    Right – Wiring penetrations have been neatly sealed with foam
    Right – Wiring penetrations have been neatly sealed with foam
    Image
    Wrong – Fibrous insulation is not an air barrier and cannot be used for sealing holes
    Wrong – Fibrous insulation is not an air barrier and cannot be used for sealing holes
    Image
    Right – Neatly cut hole has been properly sealed with foam
    Right – Neatly cut hole has been properly sealed with foam
    Image
    Wrong – Electrical bypass not sealed
    Wrong – Electrical bypass not sealed
    Image
    Wrong – Electrical bypass not sealed
    Wrong – Electrical bypass not sealed
    Image
    Right – A flexible tape is used to air seal around wiring holes in the coated sheathing.
    Right – A flexible tape is used to air seal around wiring holes in the coated sheathing.
    Image
    Right – All electrical box are carefully sealed as are all top plate-to-drywall seams.
    Right – All electrical box are carefully sealed as are all top plate-to-drywall seams.
    Image
    Right – Every wiring hole is sealed with tape.
    Right – Every wiring hole is sealed with tape.
    Image
    Right – Wiring holes in the exterior walls are sealed with canned spray foam to prevent air leakage into or out of the home.
    Right – Wiring holes in the exterior walls are sealed with canned spray foam to prevent air leakage into or out of the home.
    Image
    Right – All electric lines should be clearly labeled on the electric panel.
    Right – All electric lines should be clearly labeled on the electric panel.
    Videos
    CAD
    CAD Files
    Air seal at chase walls - plan
    Air seal at chase walls - plan
    Download: DWG PDF
    Air seal at top plate electrical penetration
    Air seal at top plate electrical penetration
    Download: DWG PDF

    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 Certified Homes, Version 3/3.1 (Rev. 09)

    National Rater Field Checklist

    Thermal Enclosure System.
    4. Air Sealing (Unless otherwise noted below, “sealed” indicates the use of caulk, foam, or equivalent material). 
    4.1 Ducts, flues, shafts, plumbing, piping, wiring, exhaust fans, & other penetrations to unconditioned space sealed, with blocking / flashing as needed. 

    Please see the ENERGY STAR Certified Homes Implementation Timeline for the program version and revision currently applicable in 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.

     

    2009 International Energy Conservation Code (IECC)

    Section 402.4.1. The building thermal envelope shall be durably sealed to limit infiltration...including utility penetrations. 

    2012, 20152018, and 2021 IECC

    Table R402.4.1.1 Air Barrier and Insulation Installation, Shafts/penetrations: Duct shafts, utility penetrations, and flue shafts opening to exterior or unconditioned space are air sealed. Table R402.4.1.1 Air Barrier and Insulation Installation, Plumbing and wiring: Insulation is placed between the exterior of the wall assembly and pipes. Batt insulation is cut and fitted around wiring and plumbing, or for insulation that on installation readily conforms to available space such insulation shall fill all space between wall and piping/wiring.

    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)

    Section N1102.4.1. The building thermal envelope shall be durably sealed to limit infiltration...including utility penetrations. 

    2012, 20152018, and 2021 IRC

    Table N1102.4.1.1 Air Barrier and Insulation Installation, Shafts/penetrations: Duct shafts, utility penetrations, and flue shafts opening to exterior or unconditioned space are air sealed. Table N1102.4.1.1 Air Barrier and Insulation Installation, Plumbing and wiring: Insulation is placed between the exterior of the wall assembly and pipes. Batt insulation is cut and fitted around wiring and plumbing, or for insulation that on installation readily conforms to available space such insulation shall fill all space between wall and piping/wiring.

    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.

    Existing Homes

    SCOPE

    In an existing home, seal around wiring to minimize unwanted air and moisture flow.

    • First, assess the current electrical system for any exposed or damaged wiring.
      • Consult a qualified electrician if any wiring is suspicious.
      • Postpone airsealing until safety issues have been resolved.
      • Obtain an electrical safety assessment if required by the authority having jurisdiction.
    • Seal around all electrical wiring and electrical boxes installed through walls, partitions, floors, or ceilings to prevent air leakage and moisture movement between unconditioned and conditioned space. 
    • Use sealants (e.g., caulk, fire-retardant caulk, fire-rated spray foam, etc.) that are compatible with all adjoining surfaces and meet the fire and air barrier specifications according to code.

    If accessing wiring and electrical boxes from the attic, see the Pre-Retrofit Assessment of Attics, Ceilings, and Roofs. If accessing wiring and electric boxes from the attic, see the Pre-Retrofit Assessment of Crawlspaces and Basements.

    See the U.S. Department of Energy’s Standard Work Specifications (SWS) for more on electrical wiring and sealing wall penetrations. All global worker safety and health and safety air sealing specifications in DOE’s Standard Work Specifications (SWS) should be followed. 

    DESCRIPTION

    In existing homes, when it comes to electrical systems, the first step is to assess the current electrical system for any exposed or damaged wiring.  A qualified electrician might need to be consulted if any wiring is suspicious and air sealing work should be postponed until any issues have been resolved, to eliminate the risk of shock or electrocution.  An electrical safety assessment may be required by the authority having jurisdiction. 

    All of the holes in the ceilings, walls, and floors for electrical wiring, outlets, light switches, light fixtures, and electrical boxes can add up to a significant amount of air leakage through the building thermal envelope (the walls, floors, and ceilings that provide the boundary between conditioned and unconditioned space) if these holes aren’t properly air sealed. Even wiring holes in interior walls can contribute to air leakage because the tops and bottom plates of these interior walls are often not properly sealed at the time of construction. (See the guide on Air Sealing Drywall to Top Plate.)

     How to Air Seal Existing Electrical Boxes and Wiring

    1. Remove switch plates and seal the gap between the electrical junction box and the drywall with caulk then install gaskets flush with the front-facing side of junction box before reinstalling the switch plates.
    2. For ceiling-mounted electrical boxes, access from the attic to caulk around the box and caulk all holes in the box with approved sealants. Find boxes by removing insulation. Replace insulation when done. Be careful not to compress the attic insulation. If attic access is not possible, caulk around the base of the ceiling-mounted electrical boxes where the box meets the ceiling drywall, from the rooms below.
    3. For wall-mounted electrical boxes, caulk all of the openings in the box (including around the wire penetrations) and seal around the box where it meets the drywall.
    4. For wiring holes (e.g., security system wiring, television and internet cables, exterior outlets, and switches) use caulk, gaskets, spray foam, or other approved sealants to seal any gaps or holes. 

    See the Training Tab for a video on how to air seal electrical boxes. 

    COMPLIANCE

    Alterations

    2015 IECC and 2015 IRC

    2015 IECC R501.1.1 / IRC N1107.1.1 Alterations – General.  Alterations to an existing building or portion of a building should comply with Sections R502/N1108, R503/N1109, or R504/N1110.  Unaltered portions of the existing building are not required to comply.

    R503.1/N1109.1 General.  Alterations to any building or structure should comply with the requirements of the code for new construction.  Alterations should not negatively impact conformance of a building or structure to the provisions of this code; that is, code conformance should be the same as existed for the building or structure prior to the alteration.  Alterations should not create an unsafe or hazardous condition or overload existing building systems.  Alterations should be such that the altered building or structure uses no more energy than the existing building or structure prior to the alteration.

    R503.2/N1103.2 Change in space conditioning.  Any non-conditioned or low-energy space that is altered to become conditioned space must be brought into full compliance with this code.  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 Sections 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.

    2012 IECC and 2012 IRC and 2009 IECC and 2009 IRC 

    2012 IECC/IRC, Section R101.4.3/N1101.3 and 2009 IECC/IRC, Section 101.4.3/N1101.4.3 Alterations – General.  Alterations to an existing building or portion of a building should comply with the provisions of the code as they relate to new construction without requiring unaltered portion(s) of the existing building to comply with this code.

    See Compliance tab. 

    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.

    Case Studies
    References and Resources*
    Author(s)
    U.S. Environmental Protection Agency
    Organization(s)
    EPA
    Publication Date
    Description
    Guide describing details that serve as a visual reference for each of the line items in the Thermal Enclosure System Rater Checklist.
    Author(s)
    Baechler,
    Gilbride,
    Hefty,
    Cole,
    Love
    Organization(s)
    Pacific Northwest National Laboratory,
    Oak Ridge National Laboratory
    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)
    U.S. Environmental Protection Agency
    Organization(s)
    EPA
    Publication Date
    Description
    Website providing the technical specifications and related documents for home builders, subcontractors, architects, and other housing professionals interested in certifying a home to the EPA's Indoor airPLUS program requirements.
    *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.

    Building Science Measures
    Building Science-to-Sales Translator

    Tight Air Sealed Home = Comprehensive Draft Protection

    Image(s)
    Technical Description

    Poorly air-sealed homes are less comfortable and cost more to maintain because they provide a pathway for drafts, cold spots, moisture, and insects into the home. Comprehensive draft protection includes a continuous air barrier around the whole house along with caulking and sealing in all holes and cracks. This includes around wiring, plumbing, ducts, and flues; where wall framing meets flooring; around windows; where drywall meets top plates and sill plates; where rim joists meet foundation walls and subfloors; etc. Spray foam insulation can be used at rim joists, floors above unconditioned space, and in attics to insulate and air seal at the same time.

    Comprehensive Draft Protection
    Sales Message

    Comprehensive draft protection minimizes air flow that can undermine a complete high-performance insulation system. What this means for you is less wasted energy along with enhanced comfort, health, quiet, and durability. Wouldn’t you agree it would be a shame to only get a partial return on your investment in advanced insulation?

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