HouseChalk
Combustion air
Combustion air is the fresh air supply that fuel-burning appliances need to burn safely and vent properly.
Why it matters
Without enough combustion air, appliances can produce carbon monoxide or backdraft. Building codes require specific provisions for combustion air.
Where people get this wrong
Sealed combustion appliances bring outside air directly to the burner. Atmospheric appliances use room air, which requires replacing that air somehow.
Real-world example
A furnace room is sealed tight after a renovation. The furnace starts backdrafting because it has no fresh air for combustion. A vent to outside solves it.
Where this hits your build
This affects daily comfort in every room. Problems often show up after move-in when certain rooms run hot, cold, or noisy.
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