Bathroom fans

Published on October 29th, 2013 | by Henri

1

Best way to vent a bathroom fan

Q.    I am installing a bathroom fan. Can I take the exhaust vent (the 4-inch diameter hose) and run it up to my ridge vent which runs the length of my ranch house? My wife does not want me to cut a hole in the side of my house. What do you think of a light in the fan?

A.    You should never vent a bathroom, kitchen or dryer vent into a ridge, gable or soffit vent — and in all but the hottest climates, never vent through the roof either.

These vents should exhaust through a gable wall. Venting these appliances through a ridge vent causes two problems: Condensation in the surrounding area that will stain and damage the roof sheathing, and wet the insulation as it drips on it;  and cause the condensate inside the vent to run down the vent and damage the ceiling, the fan and its housing (also the case when venting through the roof).

In the case of a kitchen vent, grease can also present a fire hazard. Venting through a soffit — an intake — simply takes the moisture back into the attic where you don’t want it.

It is best to vent bathroom fans by means of a bell-end, solid, schedule 20 plastic drain pipe (see illustration below). The bell-end should face toward the fan. Lay it with a slight pitch to the outside on top of the attic floor joists and snuggle 4-inch thick fiberglass batts against its sides and top. Dryer and kitchen vents should be metal and dealt with in the same way. A light/fan combination is your choice.Bell-end pipe

Facebookredditlinkedinmailby feather

Tags: , , ,


About the Author



  • lazyeight

    Too many times I have seen flexible venting ‘pipe’ collect moisture and sag between ceiling joists to the point of each bay having a large ice cube restrict the flow (New England climate). I like the idea of a thin walled, smooth pipe to the exterior.

Back to Top ↑