In our post a couple of years ago on thermal imaging of our home, we noted that we were losing quite a bit of heat through our 2 bathroom fans. In fact, if one were to put one’s hand next to the fan (while off) you could feel cold air coming right on in. While surfing the web for a solution I found these retrofit back draft dampers:
Installing one in the first floor bathroom fan was easy since the duct-work was exposed in the mechanical room. After putting one in the duct, I was, however, disappointed to still feel cold air coming through the damper, primarily through the hinge. I have seen some models where the hinge is taped, and I considered adding tape myself, but I was worried that the tape may not last/or actually cause problems. Instead, I put two dampers in the duct, which satisfactorily blocked the flow of cold air.
The second floor bathroom fan duct-work is permanently not accessible so I removed the fan from its box exposing the beginning of the duct. This was challenging only because the fan is 12′ up on a cathedral ceiling.
The downstairs bathroom went from being drafty and cool to being the warm interior space you would expect. The fans make a bit more noise as a result of the added air resistance, but I am not too worried. The Panasonic fans have variable speed motors in them and are designed to compensate for duct-work resistance.
I would recommend these dampers to anyone who is looking for easy improvements to their home’s energy efficiency. I bought mine from IAQ Source which seemed to have a better price than most. If you are building new, it would be cheaper to use an in-line backdraft damper like Fantech’s which also wouldn’t restrict the air-flow as much.
Been following your blog while building a house in NH, thanks for all the information. Did your duct cap (mounted on exterior wall or roof) have a basic damper on it?
I’m asking because we are currently installing our bath fans with Broan duct caps that have a basic damper (but they don’t look super effective), but now wondering if we should also install an additional in duct damper.
Glad you have found the blog useful. Yes, we had a basic damper on the exterior of the building, I think it might have even been a Broan. Although a cut above others since it is made of heavy gauge steel and has a bid of foam to create a better seal, it obviously was not doing nearly enough. I would highly recommend installing in-line butterfly backdraft dampers.