I am looking a putting an Air Conditioning System into a building, and I am wondering what size of air conditioner I need to do the job. The installer that I have talked to has said that 1 1/2 ton unit would suffice. My building is 78 feet by 22 1/2 feet with 12 foot ceilings. The building is made of brick primarily, it is a two story building, with a basement. The location is in Southern Wisconsin, where the hottest we see is 100 degrees, maybe in August. Temperatures are typically reach a high between 85 and 95, during the hottest days of the summer. The lows are usually around 70-85 degrees at night. Humidity being an issue during July and August. My goal is to be able to maintain 75 -78 degrees in the building. The unit would be only for the first floor. The only windows are on the west side of the building, running about 18 feet of the 22 1/2 feet width of the building. Keeping in mind that I know nothing about air conditioning. Is a ton and a half airconditioner enough, over-sized or just about right. How hard is this unit going to have to work?