quicksandfarmer
Veteran Member
If you have a noticeable inflow of air that's your makeup air.Even without combustion appliances, houses will need makeup are because of the "stack effect" that promotes leakage out of the upper areas and results in negative pressure in the lower areas. My house is two story with basement and is pretty well insulated and sealed with newer windows. I have a u-bend (trapped) air makeup tube in the basement and in cold weather I get a noticeable inflow of air. The only air use is the water heater. Everything else has outside air intakes.
I don't understand what you mean when you say "The only air use is the water heater." The water heater is a combustion appliance.