Way back machine I remember reading about an owner ( owned the building) that added a lean too on the end of his building that fed the makeup air for the dryers. , he made many rows of cinderblocks painted black and the roof was opaque fiberglass . The sun would raise the temp of the block and as the air was pulled through it it would pre heat the air thus reducing his need for more fossil fuel. I believe this was in Wyoming. Some people are always thinking.