Protecting bathroom fan from attic cellulose insulation

Hi, The exhausted air should go outside thru insulated duct. How come are you worried about dust?

On Thu 01 Oct 2009 09:36:50p, Alfred K. told us...

You should *not* be exhausting bathroom air directly into the attic. There should be a duct (preferably insulated) connected to the exhaust fan and connected to an appropriate exterior vent through the roof, eave, or sidewall of the house. This would also apply to exhaust fans anywhere in the house; e.g., utility room, kitchen, etc.

Vent moist air into an attic and it will be black with mold fairly quickly. Then follows rot, vent it as they all are supposed to be done, outside.

An insulated duct, of course, is there, connected to an ridge vent on the roof. I am asking about some possibility of contamination even with the duct present.

NO

No, you won't get contamination. However, I find it actually contrary to the building code in regards to vapor barrier sealing, that most manufacturers, even high priced ones, have many holes, opening, gaps and other areas that water vapor and drafts can easily get through. When I install such fans, I always cover every hole, opening and joint with metalic duct tape on the inside and outside of the housing. This gets as close as possible to a good vapor barrier and prevents the fan's vacuum from pulling insulation dust into the housing and drafts from entering when the fan is off.

On Fri 02 Oct 2009 11:10:46a, Alfred K. told us...

If the duct is sealed to the exhaust fan outlet, I can't imagine how dust would enter the system from the attic. You could, of course, seal all perceptible joints, corners, screw holes, etc., on the housing with duct tape.

We had a similar installation in a previous house with similar insulation. Nothing additional was required and we had no problem.

Was it in the area with very hot summers? I am thinking of potential overheating if the fan housing is sitting deep in the cellulose without any air gap surrounding it.

The motor is cooled by the airflow

On Fri 02 Oct 2009 07:05:45p, Alfred K. told us...

Yes, very hot but not humid. No problems at all. A lot depends on the quality of equipment you buy.

how high is the metal tape rated for? Some are only 200 degrees - is that a concern?

If your attic is over 200F, you have more problems than tape rating.