Heat Exchangers only work with a temperature difference between the 2 different air sources. In the winter you are EXCHANGING the hot/humid air of the "pond room" with cold/dry air from outside. The HEAT from the inside air will transfer to the cold outside air that is coming in. The humidity will not transfer through the membrane >>>>> result is an effective way to remove humidity with little loss of heat energy and no creation of new heat energy (dehumidifiers release heat).Harmonyx;1879892; said:I know zero about air exchangers. I just figured it was like a bathroom fan. I will go to rona tonight and look at them. the Coring people come sunday morning so I will need to know the dimessions of the hole they need to cut.