Infiltration and stack effect I just removed this confused section of the paragraph on infiltration Infiltration may also be slightly reduced relative to other types of hydronic or electric heating systems because with underfloor heating the air is only warmed slightly above the temperature of the thermostat setting so the temperature differential at the outside wall is less thereby reducing air infiltration due to the stack effect This is because air infiltration and exfiltration increase as the difference between inside and outside temperature AT becomes larger and so when heated air from a furnace or baseboard heater flows against relatively cold exterior walls the increased temperature differential results in a stack effect that draws cold air into the house through any cracks