Sunday, August 18

Assessing home energy use

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Dear Jim: I want to make my house more energy-efficient. I am not sure what improvements it needs, and I don’t want to invest in a professional energy audit. What do I need, and how can I do my own energy audit? — Kim G.

Dear Kim: Most houses, unless they were built with energy efficiency in mind, can benefit from improvements. The older your house is, the more likely you can significantly reduce your utility bills. Compared to most other forms of investments today, efficiency improvements to your home can provide a favorable financial return.

First, check with your local electric cooperative to see if it has a low- or no-cost energy audit program. You can get professional advice as a benefit of your co-op membership.

If your co-op doesn’t offer a program, first do a quick, simple analysis to determine how energy-efficient your house is by calculating all the energy your house uses throughout the entire year.

Keep in mind that this does not take into account the number of people living in the household or other factors that can significantly affect your energy use. If someone has a small business in a home office as I do, you need to have computers, printers and other electronics running the majority of the daytime and, unfortunately, most weekends.

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 match.

To convert various amounts of energy consumed into equivalent Btu, use the following 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: 19 million Btu

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.

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, and almost any improvement will help a lot. A number lower than 10 means significant improvements will be difficult to achieve without serious investment.

Every house is unique, but indoor air leakage typically accounts for 35 percent of annual energy consumption. Check the windows and doors for leaky gaps and joints. Also check for gaps where the walls rest on the top of the foundation, called the 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 weather stripping 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 spots, which indicate air leaks or lack of insulation, Black & Decker (800-544-6986, www.blackanddecker.com) offers a Thermal Leak Detector for about $40. It uses infrared technology, similar to professional models, to sense cold and warmth 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 that the thermostat is inaccurate, and you’re actually keeping the house warmer or cooler than you think.


Have a question for Jim?

Send inquiries to James Dulley, The Tennessee Magazine, 6906 Royalgreen Drive, Cincinnati, OH 45244, or visit www.dulley.com­­.

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About Author

James Dulley

James Dulley writes weekly newspaper columns and monthly magazine articles for more than 400 publications. All of the columns are included on his web site at dulley.com. He is a graduate of the University of Cincinnati and Harvard University.

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