INSULATION BASICS
Adding insulation is the most effective way of saving energy in most homes. Insulation works to slow the flow of heat through the ceiling and walls. It can also help by sealing air leaks. Adding more insulation will save you money during both the heating and air conditioning seasons.
Most types of insulation use air bubbles or trapped air to slow the flow of heat through the insulation. Air conducts heat more slowly than solid materials. Air trapped in the insulation slows the movement of heat.
The ability of insulation to resist heat flow is measured in units of R-value. Think of the R-value as, “Resistance” to heat flow. The higher the R-value the better the insulation does its job. The best air-filled insulations are rated about R 4.5 per inch of thickness.
There are three common types of insulation: fiber, foam, and reflective.
Fiber Insulation
Fiber insulation is available as loose fill or batts. Loose fill is generally fiberglass, cellulose, or rock wool that is blown into wall and attic cavities. It can provide better coverage than batts. R-values per inch for loose fill insulation are R-2.2 for fiberglass and R-3.2 for rock wool or cellulose.
A contractor using special equipment usually blows loose fill insulation into place. Some suppliers will rent you the equipment to blow the insulation into your own attic, as long as you buy the material from them.
I do not recommend blowing insulation into walls yourself. An experienced contractor is needed to avoid damage to the wall structure.
Batt insulation is easier to use for do it yourself projects. Batt insulation is available in rolls that are made to fit between the lumber in walls and ceilings. Rolled fiberglass batt insulation is sold in several different thicknesses. The R-value for fiberglass batts is about R-3.2 per inch of thickness.
Foam Insulation
Foam insulation comes as rigid sheets or as a spray. Rigid foam is generally more expensive than fiber insulation. It has higher R-values per inch than fiber insulation so it is a good value.
Sprayed foam insulations, such as low-density plastic foam, can achieve R-values as high as R-11 per inch. Most are spray foams are rated around R-5. Spray foams can help seal out drafts by blocking airflow and insulate at the same time.
Reflective Insulation
Unlike the other types of insulation reflective insulation, does not work to restrict conductive heat flow. It works by reflecting radiant heat away from where ever it was going. It works like a mirror.
Radiant barrier insulation is available in a couple of forms. The most common is a reflective foil made of two layers of aluminum foil. The layers of foil are put together with the shiny sides outward. Thousands of pinholes are punched in the foil to let water vapor through.
Reflective foil insulation should be installed with an air gap between it and any other materials.
Radiant barrier chips are pieces of lightweight reflective material. They can be blown into an attic as a topping over other insulation.
Evaluating the R-value of reflective insulation is difficult. Much depends on where in a building it is used. While it may have a high value of as much as R-8 in some applications, it is much less effective if relied on as the only insulation in walls or attics.
The Next Generation of Insulation
A broad array of new insulation types are in development. They hold the promise of offering values as high as R-20 or more.
One idea being researched is gas-filled panels. They use pockets of a low-conductivity gas such as argon, krypton or xenon.
Researchers are testing vacuum insulation panels. They rely on a vacuum between two layers of metal to create very high R-values. These work like a thermos bottle.
Aerogels are low-density fibers of silica or other materials. They can offer R-values as high as R-35 per inch.
Hopefully new insulation materials will be easy to use as well as cost effective.
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