This will be my first WINTER with it so I don't have a clue........So I am going to find out....I got to finish insulating the back and front walls and get my little heater installed.....I was able to get this little building back in March when that TORNADO hit here!!!.........I have no plan to put a/c in it as of right now but that may change..lolHow well does that insulation keep the heat in/out?