Installing vent fan without attic access.

homeboundJuly 21, 2010

Bathroom is under a shallow slope roof on a bathroom bumpout on a 1940's cape cod. Owner found the bathroom fan is not vented at all, which explains why it wasn't doing much. Without access from above, and with concerns about insulation and drafts, would you install a vent fan working within in the room only, or insulate and close it up since there is a window in the room anyway. The joists are running toward the window and I think they are 2x10's.

Do you think that's enough room to install from below, including insulating tightly, stopping heat loss, etc.? Do they make IC (insulating contact) vent fans?

Final issue is that the fascia is only 2x6, leaving little room for tucking an exhaust duct right under the gutter.


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Most codes will allow you to substitute a window with at least 3 s.f. of glazing half of which must open. Otherwise an exhaust fan must terminate outdoors.

    Bookmark   July 22, 2010 at 6:39AM
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Roof penetrations are done from on top of the roof. You cut the hole in the roof, pull up and connect the flex-duct from the fan and install the vent cover. Just make sure your roof penetration is not on top of a joist.

    Bookmark   July 22, 2010 at 10:23AM
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I wouldn't advise using a roof discharge on a shallow sloped roof. Don't solve on problem by creating another.

    Bookmark   July 22, 2010 at 11:22AM
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Thank you.

    Bookmark   July 22, 2010 at 2:35PM
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