Insulation For Your Home

Part 2 of 3  How Much Insulation Do You Need?

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Insulation recommendations

Due to the irregularities and inconsistencies in "old construction", all insulation recommendations are for new construction.  However, for all intents and purposes these guidelines hold for ALL buildings.  Installing vapor barriers and insulation is much easier and more economical when done during construction... which is why that new room you added on will always seem warmer than the rest of your house!

According to the U.S. Department of Energy...

"For new construction or home additions, R-11 to R-28 insulation is recommended for exterior walls depending on location (see map below). To meet this recommendation, most homes and additions constructed with 2 in. x 4 in. walls require a combination of wall cavity insulation, such as batts and insulating sheathing or rigid foam boards. If you live in an area with an insulation recommendation that is greater than R-20, you may want to consider building with 2 in. x 6 in. framing instead of 2 in. x 4 in. framing to allow room for thicker wall cavity insulation—R-19 to R-21.

Today, new products are on the market that provide both insulation and structural support and should be considered for new home construction or additions. Structural insulated panels, known as SIPS, and masonry products like insulating concrete forms are among these. Some homebuilders are even using an old technique borrowed from the pioneers, building walls using straw bales. Check the Consumer's Guide for more information on structural insulation. Radiant barriers (in hot climates), reflective insulation, and foundation insulation should all be considered for new home construction. Check with your contractor for more information about these options."

U.S. Department of Energy Recommended Total
R-Values for New Houses in Six Climate Zones

These recommendations are cost-effective levels of insulation based on the best available information on local fuel and materials costs and weather conditions. Consequently, the levels may differ from current local building codes. In addition, the apparent fragmentation of the recommendations is an artifact of these data and should not be considered absolute minimum requirements.

1. R-18, R-22, and R-28 exterior wall systems can be achieved by either cavity insulation or cavity insulation with insulting sheathing.
   For 2 in. x 4 in. walls, use either 3½ in. thick R-15 or 3½ in. thick R-13 fiber glass insulation with insulting sheathing.
   For 2 in. x 6 in. walls, use either 5½ in. thick R-21 or 6¼ in. thick R-19 fiber glass insulation.
2. Insulate crawl space walls only if the crawl space is dry all year, the floor above is not insulated, and all ventilation to the crawl space is blocked.
   A vapor retarder (e.g., 4- or 6-mil polyethylene film) should be installed on the ground to reduce moisture migration into the crawl space.
3. No slab edge insulation is recommended.

How Much Insulation Does My Home Need?

For insulation recommendations tailored to your home, visit the DOE Zip Code Insulation Calculator.

Continue to Part 3 - Vapor Barriers and Installation Tips