Published on *EGEE 102: Energy Conservation and Environmental Protection* (https://www.e-education.psu.edu/egee102)

Now that you know how to calculate hourly heat loss, how would you calculate daily heat loss?

Since there are 24 hours in a day, you would simply multiply the hourly heat loss by 24.

$$Heat\text{}Loss\left(\frac{BTUs}{h}\right)=\frac{Area(f{t}^{2})\times Temperature\text{}Difference{(}^{o}F)}{R\text{}value\left(\frac{f{t}^{2}{}^{\text{}o}F\text{}h}{BTUs}\right)}\text{}\times \text{}24hr/day$$

**What is the hourly and daily heat loss of a 15-ft by 15-ft room with an 8-ft ceiling, with all surfaces insulated to R13, with inside temperature 65°F and outside temperature 25°F?**

Once we know the heat loss rate per hour, we can determine the heat loss per day by multiplying by 24 (hours in a day).

In a 24-hour period or one day, the heat loss would be:

$$Daily\text{}Heat\text{}Loss\text{}per\text{}day=\frac{1477\text{}BTUs}{h}\text{}x\frac{24\text{}h}{day}=35,448\text{}\frac{BTUs}{day}$$
$$Heat\text{}Loss\left(\frac{BTUs}{h}\right)=\frac{Area(f{t}^{2})\times Temperature\text{}Difference{(}^{o}F)}{Rvalue\left(\frac{f{t}^{2}{}^{\text{}o}F\text{}h}{BTU}\right)}$$

Area (ft^{2}) is the sum of the area of all four walls. Each wall is 8' x 15', or 120 sq. feet, so take 4 x 120 sq ft to get 480 ft^{2} in the equation.