Sustainable insulation materials: 7 superb options

Home insulation is, at least to some extent, always an energy-saving product. As Tom Newton, manager of advertising and promotion for CertainTeed, a leading building products company puts it, "For every Btu of energy it takes to make this insulation, 12 Btu are saved every year." That said, however, there are a host of materials that can do more than just save energy -- they help save the planet, too. The following seven insulation materials are not only great at keeping your home cooler in the summer and warmer in the winter, they're also sustainable and help keep billions of tons of waste out of landfills and the environment.

Green insulation for your home

All insulation, green or otherwise, is rated by R-value. A measure of heat flow, the R-value lets you know how good at insulating a material is -- the higher the R-value, the better. R-values are additive, which means that if you need R-12 in your walls, you can stack up three layers of R-4 to get the job done. The real R-value of each insulation material listed below, however, can be determined by how well it's installed, the ease of which depends a lot on the type of insulation used and the material. Here are seven insulation materials you'll want to discuss further with your contractor if earth-friendly building products are important to you:

1. Cellulose: One of the eco-friendliest insulation materials out there, cellulose insulation is made from recycled paper. Everything from cardboard and phone books to tax forms and newspapers can be found in this insulation, made with 82 to 85 percent recycled material. The paper is treated with boric acid (or borate) to make it extremely fire-resistant. One manufacturer even demonstrated the product's fire resistance by melting a penny with a blow torch atop a bed of the insulation held in a bare hand. The R-value of cellulose insulation ranges from 3.6 to 3.8 per inch of thickness. Cellulose insulation is available in batting, rolls or as loose fill -- and it far exceeds fiberglass when it comes to sound dampening.
2. Mineral wool: There are two main types of mineral wool insulation: rock wool and slag wool. Rock wool is made from materials like basalt or diabase, and slag wool is made from blast-furnace slag, the scum that collects on the surface of molten material. Both of these man-made materials come in at around 75 percent post-industrial, recycled content and are naturally fire-resistant. The materials are available as batt or rolls and as loose fill. Mineral wool insulation has an R-value of 3.7 per inch.
3. Plastic fiber: This material looks and acts similarly to fiber glass, but it's made from recycled milk bottles (polyethylene terephthalate, or PET). The material is treated to resist fire, but it will melt if exposed to open flame. It has an R-value of 3.8 per inch at 1.0 pound per cubic foot and 4.3 per inch at 3.0 pounds per cubic foot. The material isn't for DIYers, though, because of how difficult it can be to cut and handle without the proper tools.
4. Cotton: Yes, the fabric of our lives is used as insulation -- and what a fine job it does! It's considered a rapidly renewable resource because it's harvested every year. Cotton insulation is 85 percent recycled cotton and 15 percent plastic, and even blue-jean factory trimmings can be used to make it. The fibers are treated with borate just like cellulose insulation. It's non-toxic, which makes handling and installation easy and has an R-value of 3.4 per inch. It typically costs about 15 to 20 percent more than fiberglass insulation.
5. Sheep's wool: It's like putting your house in a cable knit sweater. wool works wonders as an insulator. It's naturally fire resistant, actually singeing from flames but not catching (it's still treated with borate, just in case). It can also hold large quantities of water, which helps protect nearby timbers, although too much wetting and drying can leach out the borate. It has an R-value of 3.5 per inch, but as you might expect, it's pretty expensive, coming in at about $60 for a 24-inch roll of R-13. Because of the springiness of the fibers, this insulation doesn't degrade much over time and can last the life of your home.
6. Straw: Commonly used 150 years ago, straw is regaining popularity as insulation. A process developed in the 1930s allows adhesive-free compression into thick boards with kraft paper sandwiching the straw. The boards have an R-value of 1.4 to 2 per inch and are great for sound absorption. Some manufacturers are making multi-layered panels that are strong enough to be structural.
7. Icynene: This miraculous material is made from castor oil, a form of vegetable oil that comes from a bean. It's sprayed on like paint and then expands to nearly 100 times its volume. The air bubbles that form during the expansion make for great insulation and an R-value of 3.6 per inch. Icynene is expensive, almost three times the price of fiberglass, but that's not the only issue with this product -- it also seals a bit too well, requiring special ventilation systems to be installed.

Talk to your contractor about putting green insulation into your home, and rest easy knowing that you're saving money, energy and the planet.