But what about special soffit exhoust vents? I bought one this weekend that claims to let warm air out, but shuts when the fan is not blowing? Is that acceptable? Also, i have been warned about roof installations because apparently, if you do not patch the roof perfectly, it will certainly leak. The last Alternative is to run a good 15 ft long tube along the roof line in the attic, and run it to the wall at the back of the house. Then a wall vent can be used.