So i have a hot water tank and furnace in an enclosed room(furnace room) in the basement. The room does have an outside air intake (8") running into a hard ceiling and across to the other side of the house. When i turn the furnace fan on, close the furnace room door, and shut the door leading downstairs i get negative air pressure downstairs which causes the hot water tank flue gas pipe to backdraft. I live in a fairly new home (built 2005) and am wondering how to remedy this. If i open the door leading downstairs but still have the furnace room door shut, the backdrafting stops.
should i add a new relief (outside air to the furnace room) or have a relief opening by the door leading downstairs.
and yes i have turned the furnace off until i fix the problem.