The R-values of your insulation indicate how long it resists heat transfer. The “R” stands for resistance and each number that follows it tells you how long the insulation will resist heat transfer for an hour. The U.S. Department of Energy (DOE) suggests that you have from 16 to 20 inches in your attic, which gives you an R-value between 38 and 60.
Wall insulation is also important, but not as crucial as what’s in the attic, since the roof of your home has more exposure to the elements. The State of Oregon’s Building Codes Division requires at least R-15 in the walls for new construction. The two most common insulating products used in both walls and attics are blown-in cellulose or fiberglass batts. Each of these has an R-value of 3 for each inch of thickness.
Other kinds of insulating materials offer higher R-values for tight spaces or where there isn’t room in the wall or ceiling cavity for greater thicknesses. Foam products can have an R-value from 4 to 7.2 per inch, depending on the type you choose. Foil covered insulation also reduces heat transfer because it radiates the heat back to its source.
Heat always seeks cold and in the summer, an adequately insulated home stays cool longer and warmer in the winter. Insulation goes a long way toward keeping your cooling and heating bills low, but only as well as it’s installed.
- Fiberglass batt insulation actually loses some of its R-value when it’s crushed or compressed. Crushing the air pockets in the insulation decreases its insulting properties.
- Cellulose in the attic is likely to settle, which causes it to lose some of its original R-value.
- Leaving gaps between the studs or joists will hasten heat transfer. If you’re using faced fiberglass batts, staple down the loose edges to the studs. Cut rigid insulation so that it fits tightly where you’re installing it.
The proper R-values and careful installation will keep you more comfortable and lower the load on your HVAC equipment. To learn more, contact Roth Heating & Cooling, servicing Portland area homeowners since 1976.