Insulation- How Much and What Kind?

Insulation power is measured by what's called its "R-value." The "R" stands for "resistance" to the flow of heat. Every package of home insulation, by law, must display its R value rating.

Before you invest in insulation, be sure you do all the less expensive things that reduce energy usage first. These include: caulking, weatherstripping, installing electric outlet foam gaskets, and sealing holes for plumbing to reduce air infiltration. You also need to check the ductwork in your attic or crawl space for leaks. Insulate your water heater. Install shower flow restrictors. Plus, have your heating and cooling systems thoroughly serviced and cleaned.

Start at the top…

Once you have completed these steps; insulate any surfaces that separate heated or conditioned air from the outside. If all surfaces have some insulation, and you're ready to add more, begin with the attic. Adding extra insulation over your ceilings will probably bring the greatest return on the investment.

When you shop for insulation, compare price per R-value, not inches. For example, loose-fill fiberglass has an R-value of about 2.3 per inch, while urethane foam boards have an R-value of 5.9 per inch. You would need more than two and one half inches of loose fill fiberglass to give you the same insulating power as one inch of urethane foam board. You can determine the best buy by comparing the price of getting the total R-value that you want. The amount of insulation you need depends on the climate where you live. For most of Georgia, the Cooperative Extension Service recommends R-26 to 30 for ceilings, R-19 for walls, and R-13 to 19 under the floor or if your home is built on a slab, R-8 of rigid insulation around the perimeter of the slab.

Installing insulation…

When you're installing insulation, be sure that vents in eaves and crawl spaces are not blocked. Also keep insulation away from the tops and sides of recessed light fixtures. If you handle fibrous insulation yourself, wear protective clothing, gloves, goggles and a dust mask.

The type of insulation you need depends on where it's going to be used. You can use batts and blankets in unfinished areas—such as in the attic, under the floor and in open side walls. Batts and blankets are fire resistant, relatively inexpensive and easy for you to install.

Loose-fill insulation is suitable for finished and unfinished areas. It can be poured into place between exposed floor joints or blown into finished wall or floor cavities. Any loose-fill materials may settle in time, thus lowering its R-value. The risk of fire from loose-fill insulation is remote, except for that insulation made of cellulose.

Liquid foam can be installed in finished walls by specialized contractors. Urethane foam is expensive but has a high R-value. Urea formaldehyde or "U-F" foams can release formaldehyde vapor—especially during hot, humid weather. It can also deteriorate when exposed to light or open air.

Rigid boards are best suited for exterior wall sheathing and the floor slab perimeter, since they don't shrink or settle. You can also add them to finished walls, However, plastic foam boards are combustible and must be covered with a fire retardant material.

For more information on insulation contact your local county Extension office.