I have hot humid outside air coming in through the duct and bathroom fan in my main floor powder room that is interior. We had a mold issue in the past and had to redo the bathroom and replace the fan. Now it is still happening and it's brutal during these hot humid days. I have to run the fan non stop just to keep the humid air out. I tried calling our HVAC tech to check the duct and see if something is not properly closing but they were useless and said they don't do bathroom fans and told me to call the electrician. I explained that it's not an electrical problem but most likely some kind of mechanical problem with either the duct not properly shutting when the fan is not running or some kind of insulation issue. I am about to just go buy some insulation and shove it in there and never run the fan again to avoid the air from coming in while we are on vacation. Would someone please suggest who I can call that might be able to fix my problem? Thank you. |
You need a "backdraft damper", a way to close the bathroom fan duct when it's not in use. A handyman or bathroom remodeler should have those around, though it should have been included in your new fan. |
Can you look at where the duct coming from the fan exits your house? There should be a "flap" that closes when the fan isn't blowing.
I recommend finding a handyman, not a specialist. |
12:54 and 13:01 are talking about the same thing OP. |
There is a flap that is connected to the siding that opens with the fan is on. It looks closed when the fan is not operating but air is obviously getting in. I'm afraid we will get mold again so I run the fan all the time to keep it from getting overly humid. After we did mold remediation I hired a bathroom remodeler and it was part of my contract to fix the issue. They obviously didn't fix the issue. |
Are you comfortable playing around with it? If not, hire a handyman who can.
Maybe it's not closing well. Maybe there's a disconnect or tear in the duct allowing air in. Internet guesses are not going to get you there. |
Like already been mentioned in several posts, find where it exits the house and see if it's not flapping properly. Wasps love to nest near or in them, so they could have blocked it open. |
I would call a roofer to inspect it. |
Electrician or Gen Contractor for this job. |
Also, won't running a portable dehumidifier won't solve the mold issue? |
Both my bathroom fans vent to the attic with no damper. It's easily 120ºF up there or more on a hot summer day. You probably have the same issue. |
I don’t think they’re supposed to do that! Ours go through the attic but out the side of the house. |
This happened to us once and turns out somehow our AC setting on our automatic thermostat got reset in a storm and it was pumping OUT cold air and pumping IN the outside air! |
I know where the flap is. It's not 100% sealed shut. The opening is connected to a 5-6inch duct but the actual duct that is connected to the fan is a 4 inch duct so there is a gap and the 4inch duct doesn't come into contact with the flap, there is a 1-2" gap there as well. Since we are about to leave soon and I don't have time to call and wait around for contractors, I put some insulation inside of the opening and taped it shut with silver HVAC tape. I disabled the switch that turns on the fan and we have not had had humid air entering in. This obviously is temporary and I will deal with it when we return. Someone mentioned electrician but I think this is a purely an issue with the way the duct is at the exit point. It's not done right. I think the gap between the smaller and the larger duct needs to be sealed and I think we need a better flap that has a better seal. Is this still a handyman issue? I feel like it's a duct guy issues only I don't know who works on just ducts for bathroom fans. |
Yes, handyman can do it but a skilled handyman. |