Question

In the first lesson we talk about the heat transfer that takes place in the human body, but the same types of transfer occur for any object. For the following question, use the dimensions and characteristics of your own home. It’s reasonable to assume that walls are thick enough to block direct heat loss to radiation (without prior conduction through the walls). Windows are relatively thin in comparison and conduct more heat than walls (i.e. a double-pane glazed window has a typical value of R-2). Assume an annual yearly temperature of 10 °C.

a) What is the rate of heat lost due to conduction through the walls and windows? Make an educated guess the thickness and R-value of your walls.

b) What is the rate of heat lost through direct radiation (i.e., through the windows without conduction)? Assume that the walls don’t radiate (because their surface temperature is the same as the outside temperature).

c) What is the rate of heat lost through convection (you can assume the air is completely exchanged 3 times per day if you don’t know this value for your own house). Think of how much energy is takes to heat the air from outdoor temp to indoor temp.

d) What is the total rate of heat lost? What are the shortcomings of your model?

e) In BC we produce about 7.8 g CO2e/MJ of electrical energy we produce. Electricity costs about 7.52 cents per kWh. On average, how would it cost to heat your house for one day? How much CO2e would that heating produce?

f) How much money and CO2 could you save by lowering the inside temperature of your home by 1 C?

Answer 1