Whole House Fan vs Supplemental Insulation in Existing Attic Space
Hello,
I live in Oakland, California. My home was built in 1924 and the previous owners sprayed open cell insulation directly to the underside of roof, closing off all vents, creating an unvented attic.
The house gets quite warm during the warmer months of the year (the insulation currently there seems to not be sufficient). I’ve been considering the addition of a whole house fan in order to address the heat issue. In order to do that, the installer recommended placing fiberglass insulation directly above the ceilings and re-opening the vents in order for the fan to do its job, while leaving the open cell insulation in place. My concern is having a partially insulated, yet vented attic, and issues of differential temperatures, moisture, mold, etc. It is worth mentioning that no ducts are located in the attic. The previous owners also added a central AC unit in the basement that feeds each room via the floors. We rather save the use of the AC for rare occasions (since the whole house fan is more energy and cost efficient).
The insulation/whole fan installer wasn’t too worried about the attic venting issues, but I wanted to make sure I wasn’t missing something before moving forward with it. Also, would I be better off enhancing the spray insulation already there to adress the heat issue?
Thank you for your help!
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Replies
So he wants to retrofit your attic back to being vented. Since the work has already been done, I think you'd be better off leaving it unvented and adding more insulation. If you have a solid layer of spray foam you can run batt insulation under it, which will be less expensive.
If you want to do the fan you'll need to vent it to the outside.
Thank you, DCcontrarian.
Yes - I’ve been wondering if it would be better to add on to what is there already to address the heat. You mentioned adding batt insulation. I was thinking about adding more open cell insulation, perhaps. One of my biggest concerns is about opening the attic and moisture affecting the open cell insulation already there.