For homes with appliances that are direct vent or unvented, at what exhaust capacity must makeup air be provided?

In the context of residential installations involving direct vent or unvented appliances, the requirement for makeup air becomes critical to ensure safety and efficiency. Makeup air is necessary to replace air that is consumed by combustion processes to maintain proper pressure and ventilation within the home.

For systems utilizing appliances that draw a significant volume of air from their surrounding environment for combustion, the code typically mandates that makeup air must be provided when the total exhaust capacity of these appliances reaches certain levels. Specifically, for an exhaust capacity of 600 cubic feet per minute, it is required to provide makeup air.

This aligns with industry standards which recognize that at this threshold, the potential for negative pressure within the dwelling increases, risking backdrafting of combustion gases, which is a safety concern. Ensuring an adequate supply of makeup air at this capacity helps to mitigate these risks, fostering safer indoor air quality and more efficient combustion processes.