I am going to install a whole house fan to exhaust hot air out of the rooms on the top floor , and while I'm at it I'm thinking of installing fan(s), most likely one (1). in the roof itself to exhaust the air right out from over the ceiling of those rooms. Get it out of the rooms, into that upper area; then why not right out of that area, a hot box.
I have looked into the packaging of one of these fans at HomeDepot. Its just a 15"! (x6"?) circular shroud, and it is to be mounted anywhere- theres no flush mounting or anything, just some metal clips. The pic in the manual shows it mounted so it is blowing Horizontally - out of a louver vent mounted on the front of an "attic" - above the ceiling & below the roof, at the front of the pictured house.
I am thinking I would want to mount a fan under the existing vents on the roof, pointing up and out these vents. I do not want to screw around with the shingles outside. I've got 2 of the std. size approx 12"x12" vents, with screen inside. These vents are only about 7' apart, on adjacent parts of the roof, at the rear. The foof is about 10' x 20'. I am thinking of wiring a switch inside, beside the whole house fan switch (maybe pull cord?), and using metallic shielded cable.
Can I use this type of fan, mount it just below the vent(s) facing up? Will I need to worry about a seal to the vent to create a push vacuum? Do I need to worry about the size(s)/cfm carefully of the fan(s) wrt the whole house fan? Theres soffit venting 360, and 2 vents, need I cover (and seal) both (2) vents with fans?