Q:

# What is the CFM formula for HVAC?

A:

The formula used to determine the amount of CFM, or cubic feet per minute, a room needs for heating begins by multiplying the room's volume by the number of times the heated air gets changed hourly. Then divide the resulting number by 60 to produce the amount of CFM required.

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To determine the room's volume for the first step in the formula, the room's length, width and height must be multiplied together. When this volume is multiplied by the hourly air changes, the resulting number is the amount of cubic feet of air that passes through that room hourly. The cubic feet is then divided by 60 in the final step, since there are 60 minutes in an hour. The resulting CFM refers to how many cubic feet of air must be fed into that room every minute.

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## Related Questions

• A:

Under-floor heating involves either hot water pipes or electric heating elements placed underneath the floor of a room or an entire home, turning the floor into a radiant heater. These systems can be more energy efficient than other heating methods but also function slower and are expensive to install.

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• A:

Use the area of a room to determine the proper air conditioner size estimate, which is measured in British thermal units per hour. A 100- to 150-square-foot room needs a 5,000 BTU per hour unit, while a 400- to 450-square-foot room needs a 10,000 BTU per hour unit.

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• A:

The formula for calculating BTU loss or gain in converting CFM to BTU is temperature difference times actual CFM leakage times 1.08 equals BTU loss or gain. CFM is the actual cubic feet of air volume per minute pushed through the HVAC unit. BTU is the British thermal unit of heat removed from the room by the HVAC unit.