I purchased a brand new apartment 6 months ago.

I have noticed this as soon as I moved in, there is cold air blowing out of two electrical outlets whenever my bathroom exhaust fan is on.

These two electrical outlets are located in my bedroom which is right next to the bathroom.

Does anyone have any ideas why it's happening?


  • Are these outlets located on an exterior wall? Is the air outside cold or hot? – ThreePhaseEel May 2 at 11:36
  • These two outlets are located inside my bedroom, the bedroom is right next to the bathroom. And the air coming out is cold. – Jen May 2 at 11:42
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    Where is this apartment--country and city? There are foam seals that are placed behind the cover plate which will help. All you have to do is remove one screw to remove the cover plate. You don't have to turn off the breaker to do this. – Jim Stewart May 2 at 12:00
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    Is it possible that the exhaust air duct is not sealed properly? Or there are holes or tears somewhere on the air duct? – Jen May 2 at 12:03

Without seeing it, it's hard to say for sure. However, the fan is creating 'negative pressure' inside your apartment (which appears to be pretty close to air tight), and so that wants to equalise with the outside any way it can. Thus, air is coming into the rooms by the easiest route it can.

I'd imagine the wall your windy sockets are on is either a stud+plaster (drywall?), roughly hollow sort of thing, or else the sockets have a channel in the solid wall through to the sub-floor, or somewhere else. The air is coming from there to equalise the pressure in your apartment.

As for solutions, they probably depend on your local building regulations and the rules for changes in your block. It feels like you could remove the socket, and the back-box that holds it in the wall and put some insulation behind (or in the channel for the cables). That would probably slow the airflow, but be aware it'll start coming through some place else in your property instead.

You may be better off investigating if you can put an air vent somewhere (your windows may have some at the top which you sort of slide to open and close?), or to put an explicit hole, grilles and maybe baffles somewhere (perhaps in the bathroom outside wall? or maybe the front door into shared areas?). The idea being that it creates a deliberately 'weak' point in the air-tightness of your property to allow the fan to suck the air out and for that air to be replaced relatively easily. It would probably increase the effectiveness of the fan, at the expense of letting (potentially cold) outside air in, but at least the air comes from a known source, and hopefully more easily than through random weak spots in unexpected places.

  • Had this, the electrician fitting our sockets drilled holes in the vapor barrier... The intelligence !! – Solar Mike May 2 at 12:07
  • Ralph Bolton, thanks for the very detailed reply. I did some experiment today, very surprised by what I found. I opened up sliding door on my balcony when the bathroom fan was on, the air from these two electrical outlets almost stopped blowing immediately. Then I closed the door, the air started blowing again. Then I tried to open/close the window in my bedroom, and I got the same result. – Jen May 4 at 8:52
  • I think you are right about the fan creating negative pressure in my apartment. Air needs to come in to equalise it, so it will find the easiest route or the weakest spot if there is no air vent. However, I don't understand why the weakest are these two electrical outlets in my bedroom? Why not the outlets in the living area or kitchen? In fact, the bathroom actually is the place where the fan creates " negative pressure". Wouldn't it have made more sense if the air was blowing from an electrical outlet in the bathroom, as it has more negative pressure than anywhere else in the apartment? – Jen May 4 at 9:25
  • As @solar-mike says, it could just be that in those particular sockets the fitter didn't maintain the airtight-ness correctly - probably just a mistake during the construction. The other sockets are more correctly fitted, and so don't show the problem (or maybe just show it less? You could try putting some tape over the bedroom sockets and then have a feel around elsewhere for wherever the air is (inevitable) coming in). – Ralph Bolton May 10 at 10:12

Due to the negative pressure created by your bathroom fan, air is drawn in from the weakest points in your wall, and this appears to be the electrical outlets in your bedroom, which is not a rare occurrence, where electrical outlets are concerned. In the windy Magdaleine Islands where I live, the wind blowing through on the windy side of the house at 100km/h actually blew papers across the floor from the outlets. This means that the air barrier Tyvek or equivalent, is discontinuous. Often, the corner wrappings are the weak point or around windows and doors. Unfortunately, insulation is not an air barrier. The vapour barrier on the inside serves to impede air from inside the house from migrating into the wall, depositing moisture in the wall. It can also stop air circulating in your wall from coming into your house, though that doesn't change the fact that air shouldn't be there in the first place. Ideally, the vapour barrier is continuous behind the electrical outlet boxes or, at least, wrapped around them. Perhaps you could try that. And in doing so, you may prevent potential problems down the road of house moisture deposited in your walls. Note that negative pressure in a wall is on the leeward side.

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