DOOR INSULATION


The furnace door must be very well insulated to a minimum of 4". Some furnaces have an inner water jacketed door with a very thin outer door, others only have about 2" of insulation. Both of these doors will allow severe heat loss. Simply stated, this means more firewood is burned to get the heat you need. Look for a thick door of about 6" for best results. Watch out for hollow doors with little insulation