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Old 09-08-2010, 12:23 PM   #16
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*sigh* That's kind of what I had expected / figured as well. Probably one of the reasons a fan was never installed in the first place.

Back to the drawing board; will have to figure out another way of doing this, I guess....

Thanks again,



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Old 09-08-2010, 02:12 PM   #17
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Why you don't want to vent bathroom exhaust fans or clothes dryers into an attic:

I have seen many such examples of sheathing damage and mold growth in attics as a result of such "venting".

Best practice if you are in a cold climate is to vent through solid metal wall metal pipe, insulated to help control condensation:


Some installers recommend the use of spray foam insulation instead.

If you're using flexible pipe up make certain that there no compressed bends, or dips were water condensing out of the bath or dryer exhaust can accumulate, and with either type of vent pipe that no other bathroom or other exhaust fans are venting through the same cap:

Do not know about Canada, but if the codes are based on the International Residential Code you can not connect a positively pressurized portion of a bathroom exhaust with another bathroom exhaust or any other exhaust:

M1507.1 Where toilet rooms and bathrooms are mechanically ventilated, the ventilation equipment shall be installed in accordance with this section.

M1506.2 Recirculation of air. Exhaust air from bathrooms and toilet rooms shall not be recirculated within a residence or to another dwelling unit and shall be exhausted directly to the outdoors. Exhaust air from bathrooms and toilet rooms shall not discharge into an attic, crawl space or other areas inside the building.

Thus combined vents from standard exhaust fans are prohibited, the reasoning is that air from one exhaust will back up into other rooms and/or appliances on the combined line - the "flappers" at exhaust fan housings are not air tight. (There are exception for engineered systems in multi-unit buildings, but they don't apply in your case.)

Finally, the instructions for every dryer I've seen (except for condensing units) includes something similar to the following:

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Old 09-08-2010, 02:24 PM   #18
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Very good presentaion.

Your post is bound to have given all the Pros and Diys alike alot of food for thought. I'm sure us old salts of the hvac biz picked up at least ont new tip form your post


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