At what level of airtightness will I have problems w/ my gas furnace & water heater backdrafting while exhaust fans are running?
I am in Climate Zone, 5 northwest Missouri. I have a house built in 1958. While solid, it only has 1 1/2″ batts in the 2X4 walls and I can feel drafts in the winter. It does have tar paper as a water barrier underneath the siding.
I am wanting to remove the siding and replace and add some amount of foamboard (1″ to 2″) and tape to seal joints and windows to create the air barrier, and caulk / foam the holes in the ceiling.
When do I have to worry about backdrafting from my gas furnace and water heater when they are running with an exhaust fan? I plan to get a new stove hood that is exhuasted to outside also but not a big commerical one– perhaps 250 cfm max.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part