Michael Holigan: Normally, you want fresh air circulating throughout your house. But if too much air is coming in, your utility bills can skyrocket as you pay to cool or heat that air. One of the best ways to find out how much air is coming into your home is with a blower door test. The test should cost you about 10 cents per square foot.

A tightly sealed vinyl tarp is placed in an exterior door, and then a fan is fitted in the tarp that will force air into the house at a fixed rate. Insulation expert Craig Smith says a set of pressure gauges tells the story.

Craig Smith: By then shutting everything (all the exterior doors, windows and so forth), we can set that fan at a certain rpm and by judging the difference between the external pressure and the interior pressure tell you just exactly how much air is going out of that house.

The lowest rating you want to see is a .5, which means half of the air in your house is exchanged every hour. The highest number you want to see is a 1. Any higher than that, and you're probably paying too much in utility bills.

Michael Holigan: Craig took our readings from the field, input them into the computer, then we get our results. On the home we tested, we had a .5 natural air infiltration. We had a .81 with a 10-mile-per-hour wind. Remember, we want to stay in the range of .5-to-1 for an energy efficient and healthy home.

I'm Michael Holigan, About The House.