Mold / funk smell when attic fan is on? (floors, pool, AC)
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A strange problem, but every time my attic fan runs there is a strong funky/sewage/mold smell that comes out, but only on the main floors bathroom. The house is a 2 story with vaulted ceiling. The attic is pretty small, about 30 ft long and 3-4' high. The attic fan is on the other side of the house, yet that bathroom on the main floor gets the smell only when it's running. I've gone up in the attic and there are no sewer lines, standing water,..etc. I really have no idea what it could be, hoping someone else might
Running the attic fan puts the house under negative air pressure (relative to the outside). Air coming from under the house is a possibility, but since it is just one bathroom, I'd (sorry for the graphic nature here) be sniffing around the base of the toilet. You might have a dried out wax seal between the base and the floor. Under normal circumstances the vent pipe would take care of the problem, but once the attic fan comes on, it could suck air down the vent pipe, through the sewer line, and out around the base of the toilet. Pulling up the toilet and replacing the seal would fix that.
There can be any number of holes between attic and house. Some attic fans are more properly "whole house fans" that intentionally pull the hot air pooling at the ceiling into the attic and out of the attic vents.
Any powered attic fan of even moderate strength will find air leaks around ceiling can or top hat lights, electrical boxes, cracks hidden by molding, etc. If there is a ceiling vent in the bathroom in question that just goes into the attic space (quite common with homeowner installations) then there is a duct right there.
Hi TempesT68,
Did this just start happening or has it always been that way? Is it a full bath? And..do you have a crawl space or basement below the bathroom in question?
I have a similar problem that only started this week when my AC unit went out. Every time my atticfan runs thereisa strong funky/sewage/mold smell that comes out, but only in the main floor bathroom and little bit in the hallway. The house isa 2 story with a walk up attic and walk out basement. The atticis the length of the house. When the attic fanis on the bathroom on the main floor gets the smell only when it's running. I've gone up in the attic and checked all the ventilation connections there is no standing water,..etc. We have replaced the wax ring in the toilet and cleaned out the sink drain. Really hoping someone else can give us some ideas as to what to check next.
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