Originally Posted By: wrobedeau
This post was automatically imported from our archived forum.
The pressure in a garage must always be neutral or slightly negative to prevent fumes or exhaust from entering the living space.
Return air must never be taken from a garage due to the possibility of fumes or exhaust.
If you add supply air from the furnace to the garage you cause the pressure to go positive and thus fumes or exhaust can be forced into the living space.
A separate garage heater is recommended if the owner wants a heated space.
Commercially air is used from conditioned systems to heat garage spaces. This is done by adding an exhaust fan, a differential pressure switch and a CO or in the case of diesel CO/NO sensor to require an exhaust fan to operate providing a negative or neutral air pressure condition.
This would be too extensive for the majority of residential applications. There is always the Beverly Hills exception.
Hope this helps
Bill Robedeau P.E.
AIIZ Inspections, LLC