You need a ventilation system that recoups the heat of your house. That means you have air inflow in dry rooms, and air outflow in wet rooms. The cold outside a

You need a ventilation system that recoups the heat of your house. That means you have air inflow in dry rooms, and air outflow in wet rooms. The cold outside air going in gets heated up by the warm inside air going out. Very efficient way of keeping your house warm. That's why it's used a lot in northern European countries.