Venting for add-on to garage

[GroundLoop]

I have a 15' x 30' add on garage/storage structure that was added directly to the side of our 30' x 30' garage. It is completely isolated from the 30' x 30' garage. It has no attic area. It gets extremely hot in there and seems like it has high humidity. The 30' x 30' garage has a much higher roof and a partial attic that seems to prevent the heat build up. The roof pitch on the 15' x 30' foot add on is probably 15 deg. I would like to put some type of electric venting fan in there. Is the 15 deg pitch to small for off the shelf venting fans from Home Depot, etc? Or would a wall vent be better?

 

[buzz4041]

Try to put soffit and passive vents on the roof to get some air flowing before you go to electric fans. Even with electric fan you still have to have an intake for air to exchange or you will be creating a problem.

 

[GroundLoop]

I measured the pitch of the roof last night after work and it is (3/4)/12 - less than 1 inch. Can I still put vents on the roof. Or would I need to go with wall vents?