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Community and Q&A

How much should I worry about how bathroom ventilation fan is installed?

davidsmartin | Posted in Green Building Techniques on

I followed your advice and eliminated recessed lights in my new addition in chilly Vermont. But now when I look at pictures of the bathroom ventilation fan unit that my plumber is getting ready to install I see it sticking way up into my non-conditioned attic.

(1) Is it OK to have the unit sticking way up in my ceiling or should I be looking for a different design?
(2) Should I just pile extra cellulose on top of the unit to prevent excessive heat loss?
(3) Some people say it is OK just to end the duct in my ventilated attic. That seems risky, but is it OK to have the duct go through the attic to the gable end and through the wall there?

Thanks for all your insight,


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  1. GBA Editor
    Martin Holladay | | #1

    You definitely need to install insulation above your bathroom exhaust fan. When I interviewed Bill Hulstrunk on this issue, I asked, "Is it possible to cover bath fans with cellulose?" He answered, "Yes. That’s routine. However, if it is an older combination fan/light that takes a standard screw-in incandescent bulb, it's better to treat as if it were a non-IC recessed light fixture, and enclose it in a box before insulating."

    So heap on the insulation.

    Bath exhaust fans must be ducted to the exterior, not to your attic. Here is a link to an article that describes these installation issues in detail: Bathroom Exhaust Fans.

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