How to Add Central A.C. to Your Old House Without Breaking The Bank According to the last Census, about 50% of houses in America were built prior to 1975. Combine summer's scorching temperatures with aging homes and the result is a lot of homeowners sweating their lack of central AC. If this includes you, what are your options? Well, that depends… CENTRAL AC Does your house have pre-existing ductwork? If the home already employs a forced-air heating system — indicated by air