The purpose of insulation is to keep warm air out and cool air in during warm weather, and cool air out and warm air in during cold weather. It plays an important role in keeping your home energy-efficient, but it's easy to take for granted.

Below are answers to frequently asked questions about insulation.

Q: What is the R-value of my insulation if it measures 13 inches?

A: Thirteen inches of attic insulation really doesn't tell you much. What you really need to know is the R-value of the material. R-value measures resistance to heat flow. The higher the R-value, the higher the resistance will be. If the insulation is blown fiberglass, that 13 inches may be R-30. If it's cellulose, that 13 inches may be as much as R-45. Each material, and often each brand of the material, has a different R-value.

Q: Do ceramic coatings or products called liquid concrete or siding save energy? I've seen several ads promoting these coatings and paint additives, such as microspheres or ceramic beads that come from NASA technology, that claim to have insulative properties.

A: The Florida Solar Energy Center has tested ceramic paints and found them to have no significant advantage over ordinary paint in terms of their ability to retard heat gains through exterior building surfaces. These products are generally composed of elastometric coating products to which ceramic beads have been added. When tested side by side with the same elastrometric coating that doesn't have ceramic beads, both products have virtually the same heat-gain-retarding performance. Choosing an efficient exterior coating means picking one with a light color to reflect heat.

Q: Do attic fans save money?

A: The purchase and installation of an electric attic fan can be expensive and not very economical. In fact, electric attic fans can actually cost more to operate than they save in air-conditioning costs. With only 8% to 10% of the heat in your home coming in through the ceiling from the attic, you don't have a large margin to work with to generate major energy cost savings. Even if you were able to reduce the heat gain from the attic by 25%, the overall effect on the air-conditioning load would only be 2% to 2.5% (25% of 8% and 10%). Also, by adding an attic fan you run the risk of creating a negative-pressure situation in the attic. This negative pressure can draw air-conditioned air out of your air handler, ductwork or interior spaces through leaks and cracks.

The best thing to do is make sure that your attic is well-insulated and that you have ample exhaust and supply air vents to provide for natural ventilation. If you have adequate natural ventilation, there is no need to pay to run an attic fan.

Find an SRP-Certified contractor, or call the Arizona Electric League's Heat Pump Council at (602) 248-7767 or the Energy Management Council at (602) 266-7283 for a referral.