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jeepgrady 12-19-2012 06:31 PM

Bathroom vent insulation
When replacing a bulb in my bathroom vent fixture the fixture itself felt pretty cold. Went into the attic and the fixture was covered with insulation. The aluminum ducting is laying between the rafters going to the soffit. The ducting is on top of the attic insulation. Is this correct or should the insulation be laying on top of the duct?

Seattle2k 12-19-2012 07:11 PM

My bath vent duct isn't insulated. It runs right up to the roof. I do plan on replacing it with an insulated duct, however.

myfirstrodeo 12-19-2012 07:23 PM

Mine is insulated. I was doing a lot of work in the attic, had a few minutes, and had the materials, so it felt justifiable to me, if only for a small amount of heat savings.

If you use a foil backed insulation and seal it well with some hvac tape, you should be in good shape. I think the big box stores also sell specially designed insulation sleeves for duct work, if you prefer to sacrifice some additional money for an easier install.

jeepgrady 12-19-2012 07:36 PM

The duct itself is insulated. I just want to know whether the duct should be lying above or below the attic insulation batt.

myfirstrodeo 12-19-2012 07:39 PM

Sorry! I would just as soon leave it on top...

BOUTYM 12-20-2012 06:30 PM

Insulating the duct isn't necessarily to prevent heat loss, but rather to prevent condensation in the duct. Drawing warm moist air through a cold duct will cause water to collect on the duct walls. In the summer with a non-insulated duct this probably wouldn't be much of a problem, but in the winter with a cold attic (I hope your attic isn't warm in the winter) it can become a problem.

okeefferp 12-21-2012 06:24 PM

Mine is on top of the attic insulation. Makes it easier if you have to check it later for whatever reason.

jagans 12-21-2012 06:28 PM

I would put it under the insulation so the moist hot air does not condense and freeze on its way to the soffit.

BOUTYM 12-21-2012 07:15 PM

Just pick up some good duct insulation and wrap the thing. I have a big inline that ventilates two bathrooms and I have it wrapped from the inlets all the way to the roof vent, including the fan itself.

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