Unless you built your home with energy efficiency in mind, you can benefit from improvements. The older the house, the more likely you can significantly reduce your utility bills, yielding a favorable financial return.
But before you reject the idea of an energy audit, check with your local co-op—it might offer a low- or no-cost home energy checkup. You can also do your own simple analysis. (Go to KL 2009 Energy Guide to download our DIY energy checkup.)
To determine how much energy your house consumes annually, check your utility bills or other receipts. The calculation will be based on total British thermal units (Btu) of energy used. A Btu is about the amount of heat given off by burning a wooden kitchen match.
Once you have calculated the total annual Btu, divide this number by the annual sum of the cooling and heating degree days for your area for the current year (not a historical average), which you can find via your local weather service. Finally, divide this number by the square footage of your house.
Check for air leaks
The number for most houses falls between 10 and 20, which means a variety of energy-efficiency improvements will be beneficial. Greater than 20 means your house is very inefficient. A number lower than 10 means significant improvements will be difficult to achieve without serious investment.
Every house is unique, but air leakage can account for as much as 35 percent of annual energy consumption. Check the windows and doors for leaky gaps and joints. Check for gaps where the walls rest on the top of the foundation or sill. Heat loss (or gain during summer) through the walls and ceiling accounts for about 30 percent more. The remaining energy used is for other things like lighting, water heating, cooking, and electronics.
Holding a lighted stick of incense near walls, windows, and doors and observing the smoke trail can identify leaky spots. Move the incense around the edge and any place there is weatherstripping or a caulked joint. It’s best to test this on a windy day. Also check for leaks at ductwork seams.
If you have an all-electric house, turn on all the vent fans to create negative pressure indoors and then do the incense test. Do not use this method if you have gas, oil, or any combustion appliances because backdrafting, in which depressurization will pull dangerous gases back into the home, can occur.
If you want to check for specific hot and cold wall areas, indicating air leaks or lack of insulation, leak detectors are sold at almost anyplace that sells tools and hardware for about $40 online. It uses infrared technology, similar to professional models, to sense cold and warm on areas like walls and windows. The sensor beam turns red on hot spots and blue on cold spots.
Check the accuracy of your central furnace/air-conditioner thermostat by taping a bulb thermometer next to it on the wall. You may find the thermostat is inaccurate, and you’re actually keeping the house warmer or cooler than you think.
Fuel conversion calculator
To convert various amounts of energy consumed into equivalent Btu, use the following APPR (Annual Professional Performance Review) conversion factors:
• 1 kilowatt-hour of electricity: 3,414 Btu
• 1 cubic foot of natural gas: 1,025 Btu
• 1 gallon of propane: 91,000 Btu
• 1 gallon of fuel oil: 138,700 Btu
• 1 cord of wood: 35 million Btu, depending on hardness of wood