Combustion Air Calculator

Combustion Air Calculator 80% & 90%
Are you working on a 80% or 90%+ furnace?
Please, include the total BTU input of water heaters, clothes dryers, etc.

Now enter the size of the room where the appliances are installed.

Congratulations!!! you have enough combustion air.
Congratulations!!! you have enough combustion air. You can use 1 vent pipe.
You do not have enough combustion air. You need to install 2 vent pipes, 1 for fresh air and 1 for the exhaust vent.

You will need to add air to the room. You could use transfer grills into another space to get air from another room or get fresh air from outside of the structure. If you install transfer grills into another room, you will need 2 sets of grills, 1 set installed high on the wall and 1 set installed low on the wall.

sq in.
This is not the entire surface area of the grill but the actual free space opening of the grill please check with the manufacture product data to find the grill Free space area.

cu ft.

sq ft.

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