Keeping heat out is of somewhat limited use unless you have air conditioning, because there are a whole bunch of sources of heat (people, appliances, solar gain

Keeping heat out is of somewhat limited use unless you have air conditioning, because there are a whole bunch of sources of heat (people, appliances, solar gain through the windows, etc) that are enough to make the inside of a well-insulated and well-sealed building warmer than the outside. Also, a lot of non-US countries strongly discourage aircon on residential buildings for environmental reasons; I know the UK certainly does and Canada is probably similar.