My attached 2 car garage typically gets over 100 degrees in the summer. I have an insulated garage door. The garage has a sheetrock ceiling and attic space above that is connected to the rest of the ranch home attic.
If I put a whole house attic fan in the garage, would it cool down most of the attic or only the attic near the garage? I was thinking I would get some benefit from cooling my attic down in the evenings after the sun went down?
To ventilate a garage you want to exhaust air from inside the garage to the outside of the structure and not into the attic. The garage gets so hot that I think you should keep the ventilation separate from the rest of the house. Also there may be code requirements to separate the garage from the living space due to fumes.
If I were going to ventilate a garage, I would put in an exhaust fan in the ceiling or in an outside wall and have a fresh air inlet vent as far away as possible, on an opposite wall if possible.
Another possibility would be to have a power exhaust fan like a kitchen hood going out the roof and a vent coming in a wall or through a soffit to keep the inlet air as cool as possible. I wonder if the largest ceiling exhaust fan of the type designed for a bathroom could be vented out a soffit to avoid a roof penetration.