Finding improperly terminated bathroom exhaust fans is an almost daily occurrence as a Seattle Home Inspector. While they are mostly found on older homes or installations done by homeowners, these improper terminations can be seen even in New Construction.
Perhaps the most common improper termination is where the vent simply aims at a regular screened roof vent–the type used for venting the attic. These caps have a screen in them and perform quite well for their intended purpose. When they are used as the termination point for a bathroom exhaust fan the screen can become clogged with lint which then will direct the moisture laden air back into the attic as well as minimize the function of the roof vent.
It is best practice for each bathroom exhaust fan to terminate to the exterior at a proper cap with a back-draft damper and a screen. This screen can be maintained from the exterior. The cap should have a protrusion that extends to the interior that the pipe can attach to.
In the following picture we can see such a screened roof vent. (Note in the background the metal/rubber type flashing used around the plumbing vent pipe. While not the ideal flashing for a plumbing vent pipe, the flashing is being used for what it is designed for and has lasted as long as the roof has.)
Since I knew the house had a bathroom, and there were no vent caps through the roof, I knew enough to anticipate improper venting of the bathroom fan into the attic—assuming there was a bathroom exhaust fan (sometimes there isn’t one and they aren’t required if there is a window that opens).
At any rate, there was a bathroom exhaust fan and here is the termination in the attic.
Do you recognize the pipe flashing from the earlier picture?
Solutions to problems often create unintended consequences–unforeseen consequences. This is especially true when it involves something where the information is available–just not used–just not sought out.
By Charles Buell, Real Estate Inspections in Seattle
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