Energy Use Heating and Cooling (us)

Like David MacKay we live in a temperate climate where we have 4 real seasons and the need to stay warm in the winter is more challenging than staying cool in the summer. Further south these challenges are reversed although, perhaps surprisingly, the solutions are very similar.

1) Why does David lump cooking food in with making hot water? How much (%) of the total energy budget for hot water due to shower/bath water which is what we usually think of?

2) If David were to make his refrigerator/freezer twice as efficient as it is now (a fairly unlikely event) what is the percent change in his total heat/cooling energy use? What does this suggest to you about the importance of buying a brand new refrigerator from an energy persective?

3) David lists the energy use of a number of appliances in is home. Realizing that our refrigerator and freezer are part of the same package (so you need to lump David's numbers together) what appliance uses the most energy individually? What appliance is the second greatest user of energy in the home?

4) What is the difference between a U value and an R value when we are talking about how heat energy moves through the walls, windows, and other surfaces of our homes? What are the units of each in the SI (metric) system of units?

5) Assuming you have access to your power bill or fuel bill for your home what months would you compare to determine how much energy you are using to keep your home warm and how much you are using for food and hot water? This is the same discussion we had in class about Bruce's power bills.

6) How much more heat would you expect to flow through a double pane window (per m²) than through a standard Central Oregon wall (5.5 inches - 15 cm of fiberglass insulation)? You will need to find a table which provides you with necessary U values to compare. Be careful -- the data for windows usually ignores the thickness of the window and the data for the wall depends on the thickness of the fiberglass. Here are some wiki pages that will (hopefully) help. Walls (this is a table of k values - note the units:).... Windows... metric R Values (RSI) for building materials. For this last table notice that units for RSI are good but they are actually for a single inch of material. You need to multiply this number by the thickness of your insulation (in inches which is irritating) and then invert it. Alternatively you can just use the k values from the Walls table above and put the thickness in m into L in the equation.

7) Take one room in your house that has at least two outside walls and sketch it out. Figure out, in rough terms, how much surface area each of the 6 walls of the room (counting the ceiling and floor) has, how thick each one is, what the terperature on the outside is, and how big are the windows. I'm not concerned with high precision here but rather a general sense of data so we can explore it in class.