Ceiling and Sidewall Insulation R-Factor Guidelines

Within the past few years, the Department of Energy has developed new insulation guidelines. These are minimum standards. There is absolutely nothing stopping you from installing more insulation. The only thing you need to consider is the long-term payback. For example, I built my home over ten years ago. At the time, the guidelines for ceiling insulation were an R-30 in my climate zone. I doubled that and installed an R-60 ceiling of blown-in fiberglass. Did I waste my money? I think not. My neighbors fuel bills for houses smaller than mine are nearly double! I save approximately $1,000 per heating season. I probably save an additional $400 during the cooling season. Some of these savings can be attributed to thicker sidewall insulation, an air infiltration barrier, and tight building practices. However, in your existing home, you might save $150 to $200 per year on average. If it costs you only $300 more to upgrade to an R-60 or more, do so! Within two to three years, you will be saving money.

The U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy, has also published Technology Fact Sheets on basement insulation; crawlspace insulation; slab insulation; wall insulation; and ceilings & attics.

The map below is vastly different from the old guideline maps that showed only five climate zones. If your city is located on the borderline of one of the zones, always upgrade to the higher zone. It will not cost that much. Ask the manufacturers for installation guidelines. You need to learn how to do it right. Knowledge is power!

PHOTO CREDIT: US Department of Energy

* "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." ... US Dept. of Energy

Insulation Zone Map Guide

The following table shows the different R-Values that you need to achieve in ceilings, walls and floors with respect to the zone you live in. Study it for a few moments and it will make sense.

PHOTO CREDIT: US Department of Energy

(A) R-18, R-22 and R-28 exterior wall systems can be achieved by either cavity insulation or cavity insulation with insulating sheathing. For 2 in. x 4 in.x walls, use either 3-1/2 in. thick R-15 or 3-1/2 in. thick R-13 fiberglass insulation with insulating sheathing. For 2 in. x 6 in. walls, use either 5-1/2 in. thick R-21 or 6-1/4 in. thick R-19 fiberglass insulation.
(B) 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.
(C) No slab edge insulation is recommended.

NOTE: For more information, see:

or Energy Savers - Tips on Saving Energy & Money at Home from U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy.