Home >> Science & Nature >> Science

How to Convert Heat Loss to CFM

Designing buildings and structures involves a myriad of different tasks and things to think about. Heating is of primary concern from a monthly expense point of view. Measuring the heat loss of your structure provides you with the fuel required to maintain the comfort level in the structure. Once you have measured the heat loss of the structure, you can calculate the amount of fuel required on a daily or monthly basis.

Instructions

- 1
  Look up the amount of heat provided by your heating fuel type. Each type of fuel provides a different amount of heat, measured in BTUs, per unit volume. Propane and natural gas are two fuels that you quantify volume in cubic feet. The flow rate in cubic feet per minute (CFM) required to match the heat loss will provide you with an estimate of monthly costs. For example, assume you heat by propane. The amount of heat provided by propane when used as fuel is 1034 BTU per cubic feet.
- 2
  Determine the amount of BTUs required to replace the amount of heat lost from the structure per unit time. You can choose the most convenient time base for your measurements; you can select minutes, hours or days. Continuing the example, assume the structure loses 10,500 BTUs per hour.
- 3
  Convert the BTUs per unit time to BTUs per minute. Your measure of fuel usage must use the same time base. Continuing the example, divide the heat loss per hour by 60 to yield the heat loss per minute. 10,500 BTU/hr * 1 hour/60 minutes = 175 BTU per minute.
- 4
  Calculate the amount of fuel required to provide the amount of heat lost. This is determined by dividing the amount of heat loss per unit time by the amount of heat provided by your type of fuel. Continuing the example, 175 BTU per minute divided by 1,034 BTU per cubic foot propane, 175 / 1,034 = 0.169 cubic feet per minute.

Science