In the summer, I work in a storage building made of wood but the roof is metal. I tried foam insulation but it hardly works at all. I installed cardboard boxes flattened out (several layers) and left space above them to form a place for hot air. It works great - also use a fan to blow across my saw to blow out the sawdust and hot air. Put in a little thermometer and if it gets 92 degrees - I quit until it cools off. There is plenty of sanding and finishing to do under the trees where it is cooler.
