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Air Sealing Electrical Wiring

Scope

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

Air seal around all electrical wiring and electrical boxes installed through walls, ceilings, and flooringto 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.

  • 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.

  • 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.

  • 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. 

  • 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.

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.

Training

Right and Wrong Images

Presentations

None Available

Videos

  1. Electrical Wiring
    Publication Date: July, 2015
    Courtesy Of: Train2Build

    Video describing how to properly install electrical wiring.

CAD Images

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, Rev. 08)

ENERGY STAR Certified Homes (Version 3/3.1, Revision 08), 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

ENERGY STAR Revision 08 requirements are required for homes permitted starting 07/01/2016.

DOE Zero Energy Ready Home

Exhibit 1: Mandatory Requirements.  Certified under ENERGY STAR Qualified Homes Version 3.

2009 IECC

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

2012, 2015, and 2018 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, 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

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

2012, 2015, and 2018 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, 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.

This Retrofit tab provides information that helps installers apply this “new home” guide to improvement projects for existing homes. This tab is organized with headings that mirror the new home tabs, such as “Scope,” “Description,” “Success,” etc. If there is no retrofit-specific information for a section, that heading is not included.

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. 

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

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

    Case study about one builder's conversion to high-performance building in the hot-humid regions of the Atlantic seaboard.

  2. Author(s): PNNL
    Organization(s): PNNL
    Publication Date: October, 2012

    Case study detailing techniques used to prevent thermal bypass in new homes.

References and Resources*

  1. Author(s): Lstiburek
    Organization(s): Building Science Corporation
    Publication Date: May, 2009

    Brochure about creating an air barrier by sealing drywall assemblies.

  2. 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.

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

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

  4. Author(s): U.S. Environmental Protection Agency
    Organization(s): EPA
    Publication Date: December, 2015

    Webpage with links to Document outlining the program requirements for ENERGY STAR Certified Homes, Version 3 and 3.1  (Rev. 08).

  5. Author(s): Lstiburek
    Organization(s): Building Science Corporation
    Publication Date: January, 2010

    Fact sheet providing detailed information about air sealing attics.

  6. Author(s): U.S. Environmental Protection Agency
    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.

Contributors to this Guide

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

Last Updated: 12/18/2017