Comments on: I Blew a Gasket — Air Leakage at Electrical Switches and Outlets

By: Greg La Vardera

Greg La Vardera — Mon, 06 May 2013 00:42:43 +0000

Can't let this go by without
Can't let this go by without comment. For new construction in heating climates, the easiest way to achieve a high level of air-tightness is a Nordic layered wall system like my USA New Wall model wall systems.

Its very simple. A wiring space behind the drywall keeps all of the boxes and penetrations inside of the vapor control sheet which also is the primary air-tight boundary for the house.

This is the easiest way to do it. Pouring labor into sealing electrical components, with fancy boxes or not, is just crazy. Putting labor into an air-tight exterior as well as an air-tight vapor retarder at the interior is also twice as much work. Does not matter if you are taping ZIP outside and "air-tight" drywall inside, its twice the work. Does not matter if you are doing foam and batt inside, and tyvek outside, its twice the work.

This has already been vetted by years of building science and construction in Scandinavia. They have arrived at this because it is the most effective and the easiest to do. We are like children in the sandbox here when it comes to air-tight building. We are trying all kinds of techniques here, the vast majority of it rubbish.

By: Colin Genge

Colin Genge — Wed, 13 Feb 2013 22:03:17 +0000

I totally agree. Outlet
I totally agree. Outlet leaks are merely a symptom of the larger problem that the wall is being filled with outdoor air. Putting band aids over the outlet is simply a feelgood gesture with no overall impact.

Walls full of cold outdoor air will cool people by radiation and force them to increase the thermostat setting to compensate.

Yes, seal them at their source.

By: Jeff DeSart

Jeff DeSart — Wed, 13 Feb 2013 18:20:19 +0000

Leaking outlets/switches are
Leaking outlets/switches are only a symptom of the real problem. Your thermal envelope is not intact. Interior walls are not part of the thermal envelope. You must go seal top plates and penetrations in the attic and penetrations through the floor in the crawlspace to eliminate air leaking into the walls. If you just seal the outlets/switches you will still have unconditioned air breaching the thermal envelope and entering the home, even if its just filling the wall cavities. Also,I find it hard to believe that the cost to seal outlets/switches can be justified by the savings.

By: Mike M

Mike M — Wed, 13 Feb 2013 04:10:04 +0000

Mark J: One problem we have
Mark J: One problem we have in far north climates is that moisture gets into walls, which causes mold and rot, especially thru outlets and switches if the above noted sealing methods are not employed. The winters are long enough that drying doesn't occur until summer.

Also, in cold climates, the heat lost by infiltration adds up, especially trying to heat -30F air to 70F. Makes for a drafty house.

An older but labor intensive sealing technique that still works is to put a 12"x12" piece of 6-mil poly behind the box prior to mounting it to the wall, and wrap the box with the poly. Wherever a wire goes through the poly wrap, apply Tremco acoustical sealant ("black death") around the wire at penetration. Then you also apply Tremco to the interface of this homemade box wrap to the main vapor retarder, also sealing it down with red 1-mil 3M vapor barrier tape. Obviously these factory made vapor retarder boxes are easier to use than home-made ones I described.

I would recommend using fire-block spray foam (versus regular spray foam) when sealing around wires, especially with receptacles where high usage appliances can cause the wires to run warm. This might prevent a fire.

By: Robert Post

Robert Post — Tue, 12 Feb 2013 23:34:21 +0000

&

Seal building envelopes, not electrical boxes. Gaskets don't work.

By: Mark J.

Mark J. — Tue, 12 Feb 2013 20:55:09 +0000

@Bob Seaton: I actually sat
@Bob Seaton: I actually sat down with a measuring caliper to see what size the sum of the holes is, for the electric part of the outlet is 0.2 sqin. It seems clear to me that if significant leakage occurs it must be around the edges of the wall plate. And most of those I see, do not have enough of a gap to plausibly add up to even 0.5 sqin. I am sure nobody intended to DOT (dwell on trivia) but we might indeed fall into that trap.

By: Mark J.

Mark J. — Tue, 12 Feb 2013 20:38:23 +0000

@Bob Seaton: You mentioned 32
@Bob Seaton: You mentioned 32 outlets *might* be equal to 0.5 sqin, which would equate to a 4-inch square hole. 16 sqin total.

Well my blower door report claimed total leakage was equivalent to 393 sqin which would confirm electric outlets as a really small part of the total. This house is measured at 5.3 ACH50 so it is not the leaky sieve you probably want to argue. My utility bills are rather low and I attribute that to air sealing virtues -- particularly ducts and can lights rather than the relatively minor aspect of plugs.

If electric outlets were important, would it not be a worthwhile virtue to keep them filled with plastic dummy plugs as used for baby safety? Would we not develop little swinging door covers as outdoor fixtures use? I still need to see more measurements to convince me my attention shouldn't be mainly on other things.

By: Allison Bailes

Allison Bailes — Tue, 12 Feb 2013 17:56:57 +0000

L.T. Gallop
L.T. Gallop: Apparently your thinking has not advanced past the myths of the 1970s. We have this thing called building science, though, and I suggest you start catching up by reading this recent article I wrote:

Why Do Airtight Homes Need Mechanical Ventilation?

By: Kim Shanahan

Kim Shanahan — Mon, 11 Feb 2013 23:07:45 +0000
For heavily textured walls, a
For heavily textured walls, a gasket behind the cover plate is a must, or even better, caulk the plate to the drywall. Just make sure it is done after final electrical inpsection or the electricians will have a fit. Another big gap is usuallly around the box itself and the drywall, often too wide to caulk, which means more foam. If one expects to get down to PH tightness, there really is no choice but to do "all of the above".

By: Adam Gloss

Adam Gloss — Mon, 11 Feb 2013 21:33:23 +0000
The products you suggested
The products you suggested are great to use when you are building or remodeling a home, but what can be done for built homes in a retro-fit application? Even if foam gaskets and caulk are not perfect, they seem to be the only solution available at this time.