Question:

Hi Glen, I have a bedroom which partly extends above a garage. Basically, I have noticed that the section of the garage ceiling which covers the room above is insulated but also contains a furnace air duct which supplies air into this cavity. There is no cold air return, so I am concerned that this may be a dead air space which could be prone to mold. Should I cap this air duct and insulate this cavity without the duct or is it possible to add a return in on the floor above this cavity. Regards, Wayne

Answer:

There must be a return to match this supply duct or you risk having a pressurized space. If the space is indeed pressurized, the risk is that warm, relatively moisture laden air will be forced into a colder cavity causing condensation, this mold etc. Two choices: Remove the duct and spray foam the floor, or add a return. In all cases, ensure the garage space is sealed 100% air tight from this cavity, or you may risk much more than a little mold. Note that even spray foam insulation may leave the floor a little cool but it is probably the best option given the circumstances. Best Regards, Glenn

Answered By: Glenn Wiseman

More Questions & Answers ...