A draft hood is a metal fitting installed at the vent outlet of atmospheric furnaces and water heaters that prevents excessive draft from pulling air into the combustion chamber. This device allows air to enter and exit freely, stabilizing draft pressure and preventing flue gas spillage. Draft hoods are required by code on naturally drafted appliances operating without mechanical venting assistance.
Function and Design
The hood sits above the appliance and contains an opening through which combustion gases exit. If excessive draft develops from a tall chimney or windy conditions, the opening allows dilution air to mix with flue gases, reducing pressure. The hood also protects against wind-driven rain and downdrafts that could reverse flue gas flow.
Modern Alternatives
Draft hoods are becoming obsolete as atmospheric furnaces are phased out in favor of sealed combustion and condensing models. High-efficiency furnaces typically use power vents or induced drafts with motorized blowers instead. Current code changes in many jurisdictions restrict or prohibit atmospheric furnaces, accelerating transition to draft hood-free heating systems.