Exhaust Fans Need to be Checked!
2011, November 28th
I recently was called in to check on two exhaust fans that another contractor installed in a client's home. The complaint was simply that they weren't working. Both were Panasonic units, some of the best around. The fans were running but the odors and water vapor weren't being exhausted from the two bathrooms.
I started with the first floor unit: I removed the grill and turned on the exhaust fan. I found that air was blowing out of the fan back into the room. Under closer inspection I noticed the installers left out one of the three screws that hold the unit into the housing. This caused the unit to sag inside of the housing and misalign the flap that keeps the back flow of cold air from blowing in to the room from outside when the fan is off. It was stuck on the side of the housing- In the closed position. As a result no air was able to exit. I installed the missing screw which pulled the unit securely into the fan into the housing. Now the flap aligns properly and it floats up with the air pressure when the unit is switched on. The exhaust fan is working great and it's very quiet!
Then I inspected a larger exhaust fan on the second floor. Seeing as the first one was incorrectly installed I guessed I'd find a similar problem. When I turned the fan on I could, again, feel air pressure blowing into the room. It turned out that this fan hadn't been ducted at all! After removing the unit from the housing I discovered that the flap was stuck closed because the attic insulation was shoved up against the exhaust port. I was able to reach through the exhaust pipe and move insulation away from the port. Of course, now the exhaust goes into the attic. The solution was more involved: I supplied the correct ductwork and a roof jack to make it right.
Many bathroom and kitchen exhaust fans are not installed correctly. Finding exhaust fans ducting directly into the attic is very common in my business. Water vapor from the bathroom exhausted into the attic can create problems such as rot and mould.
In the case of an exhaust fan that is ducted into the attic an automatic attic exhaust fan that goes on in the summer will create enough vacuum to actually suck air out through the exhaust fan. That would be air conditioned air in the heat of the season. This will in turn raise cooling costs. If it's a kitchen exhaust fan, then kitchen odors and grease are blown directly into the attic. This is a fire hazard and it makes a terrible mess.
These repairs are an easy fix with a bit of roofing material, metal ductwork and a good carpenter! And if the fans are aging, it's a good time to replace them with newer more efficient and quieter units!
Please let us know if you would like a free inspection of your fans!
I don't recommend many exhaust fans for bathrooms: I have always been impressed with the Panasonic exhaust fan. It's been often imitated, and some come pretty close, but it's still the most innovative and solid unit I've installed: http://www.panasonic.com/business/building-products/ventilation-systems/products/whisper-green.asp
