Roof vent or fan for hot shop?

[Charles Lent]

When you want to get hot air out through a vent you have to remember that you have to let an equal amount of cooler air in some place, preferably lower in the space. Soffit vents, an open window, etc. would work for this air inlet. Just remember that to get the air out at the top you have st have some place for that same amount of cooler air to get in.

Charley

[Howard Acheson]

Keep in mind that a roof fan will never produce cooling less that the outside temperature. All you accomplish is to circulate the outside temperature air up and out of the ceiling. The replacement air is still the same as the ambient outside air.

[Prashun Patel]

I hate more roof penetrations than are necessary; they're just maintenance risks.
What is the ceiling height? Can you just mount an exhaust fan (think vented range hood) at a high point on the wall? I think you'll catch more ambient dust that way too.

Also, you can increase your airflow by also venting your dc outside. I wish I could do that even just for the dust collection efficiency of it.

[Bruce Seidner]

Being in my garage shop here in Savannah is like being in one of those aluminum boy scout radiant baking racks as kids we used to bake cookies on. I work with the two garage doors open and the back door to the outside has a 24"Harbor Freight round shop fan that blows air in creating a decent breeze.I was looking for one of those big pulley round shop fans but they are expensive and too big for the stub of a hallway to the back door. I have a couple box fans inside I aim that evaporate the sweat off me. I might try mounting a piece of hardboard to cover the door opening and experiment with reversing the fan so that it pulls air out the back and see if that makes a difference. It is a brick attached garage and the external wall just radiates heat. The previous owner insulated it and covered the whole wall with plywood. I was blessed to have such a thoughtful former owner. Now the house is a rental and I am not able to do much structurally. But with such a large fan it creates enough air that it is no longer an oven, just in the 90's like everywhere else down here May through October. I take breaks in the air conditioned kitchen between bouts to cool down.