How to Air Seal Outlets and Switches


Key Considerations:

In most construction distribution of electric power, communication and control involves "punching through" interior finish walls. In much construction and in most residential construction, the interior finish wall is also the air barrier. The work "ceiling" used to refer to interior plaster or other finish of both walls and ceilings. Today's alternate spelling "sealing" has come to mean "plugging leaks." Back boxes for line current and other devices create unintended air leaks that must be detailed to restore continuity to the air barrier.

This mostly applies to wiring locations on exterior walls, but interior walls often have connections to cold attics or cellars.

Possible downsides:

Detailing the inside of electrical rough-in boxes for air tightness is time consuming and messy. Moreover, one must not clog the boxes or wiring runs with insulating material (think "foam") that could trap resistance heat and create a fire hazard. Detailing of any kind with sticky sealants in finished, or even semi finished space requires a practiced hand to avoid making a mess. It also requires confidence and experience to perform at any economic rate.

Recommendations:

For outlets, does the escutcheon plate fit tightly to the wall? If so the remainder of leakage will be through and around the duplex device itself. For this common condition, use plastic child proofing blank-offs to "stopper" most of the rest of the air movement at unused outlets, which is most of them in most buildings. A quick & dirty fix for those in constant use is clear tape. Just stab the plug though the tape.

For switches, phone and "comm" jacks and other controls, precut gaskets that fit under escutcheons are the quickest fix.

Buildings under construction can take advantage of specially designed air tight back boxes with air tight wire perforations that seal to surrounding wall finish, usually sheetrock.

In the design phase, consideration can be given to surface wiring or other kinds of "raceways" that keep wiring completely inside the air barrier. Planning wiring "home-runs" to radiate from interior chases minimizes wiring in exterior walls and penetration of the interior finish there. These are established practices in commercial construction for reasons of economy and service access. Admittedly, they are not to conventional residential taste nor reflected widely in residential trade practice. For certain building uses, surface wiring is actually preferred for service access and ease of changes.

A building that is "skinned" to the outside will likely have all wiring inside the air barrier. See discussion of skinning under Corners and Ganged Framing elsewhere in Insulation-Guide.



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