| A furnace blower is a powerful fan that sucks air into the return ductwork and blows it out the supply ductwork. Pressure and air movement across the thermal envelope are induced whenever the path between the supply and return ducts is blocked. |
If this is a bathroom with no return or transfer duct, the blower will force warm moist air into the framing.
As warm air is forced out of one part of the house, cold air is drawn into other areas to replace it.
Blocked conditioned air will induce increased energy use and combustion appliance zone depressurization.
