Q–What is meant by air changes per hour?
A–The term is a measure of how much air is flowing into and out of your home. The number of air changes per hour is important to know when measuring the “tightness” of a house. The term has become widely used because of concerns with the effect a well-sealed house might have on indoor air pollution.
Experts recommend that the volume of air in a house be replaced about every two to three hours. The desired air change rate per hour would be between 0.33 and 0.50 when the house is not being ventilated.
Rates higher than these mean that there are openings that are letting too much air flow into and out of the house. Rates lower than these may mean the house is tight, with potential problems from indoor air pollution caused by building materials, chemicals, smoking and other factors within the home.
Keep in mind that energy experts still disagree over the issue of well-sealed homes and whether they contribute to indoor air problems.
Q–I’m intrigued by the thought of using solar energy to power things in my house. Can it be done, or is it still something for the future?
A–It can be done, but I don’t think you want to–not just yet anyway. Researchers have made progress in recent years in improving the efficiency of photovoltaics (solar cells), but it will be some time before solar is cost-effective when compared with power from the electric grid. If your home is served by the local utility company, then solar energy will be far too expensive to use as a substitute.
The cost-effective use of photovoltaics today is for buildings that are not connected to the electric utility grid. In the United States that means vacation homes and other buildings located in very remote areas.
