DIY Calculating Home Heating Costs

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It can be very expensive to heat a home in winter, especially in areas which are frequently subject to freezing temperatures. The first step to saving money is to calculate home heating costs. Heat is measured in BTU’s ( British Thermal Units). One BTU is the amount of heat that would be needed to increase the temperature of one pound of water by one degree F.

1. Begin by obtaining the insulation R-value of the walls, roof, and floor. They will have different R-values. The R-value is the amount of heat loss (BTU) per hour per square foot of wall (or roof or floor) space multiplied by the difference in temperature between the inside and outside of the building. The loss per hour is then multiplied by 24 to obtain the heat loss per day. The formula is:

Heat loss = Q/t Q = Area (sq. ft.) x difference in temperature ( degrees F)
t = thermal resistance (R-factor)

2. Calculate the amount of heat loss through the walls using the above formula with the R-value of the walls.

3. Calculate the amount of heat loss through the roof using the above formula with the R-value of the roof.

4. Calculate the amount of heat loss through the floor using the above formula with the R-value of the floor.

5. Calculate the loss per degree day. A degree day is the amount of heat necessary to heat a building for one day when the outside and inside temperatures have only a one degree difference.

(difference in temp) x (# BTU loss per day) = the number of BTUs necessary to maintain the inside
temperature for one day

6. The weather service can provide the average number of heating days for your region of the country. Calculate the seasonal home heating costs by using the answer from the above step and multiplying it by the number of heating days.

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