What is the normal return air requirement for forced air furnaces?

The normal return air requirement for forced air furnaces is typically around 900 cubic feet per minute (CFM). This measurement is critical in ensuring that the furnace operates efficiently and effectively. Adequate return air is necessary for the furnace to properly circulate and condition the air within a space, maintaining a consistent temperature.

When the furnace draws in enough return air, it can heat the space evenly, preventing issues such as cold spots and ensuring that the heating system doesn't work harder than necessary. Insufficient return air can lead to system strain, higher energy costs, and reduced comfort levels.

Understanding the return air requirement is essential for HVAC system design and for ensuring compliance with local building codes and regulations. The specific requirements can vary based on the size of the furnace and the layout of the home, but 900 CFM is a generally accepted standard in many applications.