(Editor’s note: The following is the second of an eight-part series designed to reduce energy costs in the home.)
Fact or Fiction? “Insulate your home and you’ll cut your energy bills in half.”
Fiction. Many people have seen little or no in energy cost after adding insulation alone.
An R-value is a measure of thermal resistance. Newly recommended R-values for this region are R-49 in attics and R-19 in walls. Let’s first explore the three major types of insulating products available on the market today.
Fiberglass insulation is by far the most common, probably due to the affordability and the ease of installation for homeowners who prefer to install it themselves. The single most important problem with fiberglass insulation is that it is very porous and air has the ability to move right through it. Have you ever felt cold air coming through electrical outlets, even though you know you have insulation in the walls?
Cellulose is made entirely from recycled newspaper and magazines and is a blown-in type of product. It is denser than fiberglass, and R-values per inch of insulation are higher than that of fiberglass due to its density. Sealing before installation is highly recommended, especially in attics.
Spray foam products not only insulate very well, they are also the best sealing agent. Spray foam is initially the most expensive, but usually the most cost-effective form of insulation in terms of energy savings. In attics, existing insulation must first be removed in order to apply foam insulation. Walls with minimal insulation can also have non-expanding foam injected into them.
The most important part of insulation is to stop thermal (heat) transfer. Even the most well insulated homes can still be energy wasters if not properly sealed. If air moves through insulation, R-values are considerably diminished. Air sealing not only stops air from moving into the home, it also stops the allergens, dust and other unhealthy contaminants in the air from entering your home as well.
Before attempting to add insulation, I highly recommended having a professionally performed negative pressure test done on your home with an Infiltrometer blower door. This will find where all the air leaks are. That, coupled with adding insulation up to recommended R-values, will certainly reduce your energy usage.
Look for the third part of the series next week, where I’ll discuss air seal-ing and where to find the worst offenders.
Joel Wensley is a licensed mechanical contractor in the state of Michigan and president of Mechanical Heating & Cooling in Dearborn Heights.