i have a 2.5 ton unit in my house. house is 2500 square feet, 1321 upstairs and 1130 downstairs. unit is in the basement with trunk line run in the basement with 6 inch cut off to all areas of the house. i am in the process of replacing horrible flex duct with hard duct to help and is making a big difference. new dorrs and windows installed in basement have helped as well. will be replacing the upstairs windows eventually. is the 2.5 ton enough for the house if all is complete to be energy efficent?