Sorry so late in responding. My woodworking shop is 2x6 construction and I insulated it well. The big exception is I had 1 40' wall that was not insulated and only had 7/16 osb with tyvek on the outside all summer and it stayed cool without excessive running. I was frustrated trying to figure out the right size for my shop. I used several calculators and got several different answers. The common size recommendation was 18,000 btu and I decided to go 24,000 btu. After I ordered my unit and was waiting on it I was reading the Mr. Cool site and used a tool on their site that recommended 36,000btu and I was worried, but it worked out for the best. I also put in a ceiling fan to move air but don't use it very often.