Electrical Wiring

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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. Reference

  • 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. Reference

  • 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. Reference

  • 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. Reference

  • 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. Reference

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.

Scope

Electrical wiring

Air Sealing

Electrical Wiring

  1. Using a saw or drill, cleanly cut all penetrating holes no more than 1 inch larger in diameter than the penetrating object to allow for proper air sealing.
  2. Seal all gaps and holes to unconditioned space with caulk or foam. Fibrous insulation is not an air barrier and cannot be used for sealing gaps.

Training

Right and Wrong Images

Presentations

None Available

Videos

None Available

CAD Images

Compliance

ENERGY STAR Version 3 (Rev. 07)

Thermal Enclosure Checklist, Air Sealing. Penetrations to unconditioned space fully sealed with solid blocking or flashing as needed and gaps sealed with caulk or foam.

DOE Challenge Home

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

2009 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.*

2009 IRC

Table N11402.4.2 Air Barrier and Insulation Installation, Shafts/penetrations: Duct shafts, utility penetrations, and flue shafts opening to exterior or unconditioned space are air sealed. Table N11402.4.2 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.*

2012 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.*

2012 IRC

Table N11402.4.1.1 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.*

*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: 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): BSC
    Publication Date: May 2009

    Brochure about creating an air barrier by sealing drywall assemblies.

  2. 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.

  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): Lstiburek
    Organization(s): BSC
    Publication Date: January 2010

    Fact sheet providing detailed information about air sealing attics.

  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.

Last Updated: 08/15/2013

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