EGEE 102
Energy Conservation and Environmental Protection

Calculating Hourly Heat Loss


As we have learned, most heat is lost through a house's walls through conduction. One of the three factors that affect heat loss is a wall's capacity to resist heat loss.

We will now look at how to calculate the rate of heat loss of the walls of a house, using the following formula:

Heat Loss ( BTUs h ) =  Area ( ft 2 )×Temperature Difference ( °F ) R-Value( ft 2  °F h BTUs )

From the above equation it can be seen that once the house is built, these two variables will NOT change:

  • The area of the walls
  • The R-value of the walls

The only variable that will change is the temperature difference between inside and outside.


Calculate the heat loss for a 10 ft by 8 ft wall, insulated to R-value 22. The inside temperature is maintained at 70° F. The temperature outside is 43° F.

Please watch the following 2:25 presentation about Hourly Heat Loss:

Hourly Heat Loss - Problem #1