New Home Insulation Options
April 16, 2014
Whether it’s pink, white, yellow, or blue, all insulation is at least a little bit “green.” After all, anything that saves so much energy gets high marks for environmental friendliness. But increasingly, the materials we put inside our walls and ceilings are turning a deeper shade of green, with old standbys like fiberglass and foam cleaning up their acts and natural and recycled alternatives now widely available.
To be sure, in an industry whose products have been both praised and litigated, the earth-friendliness of house insulation depends to some degree on whether you’re assessing what it’s made of or simply how it performs. Consider this very green bottom line from a segment of the industry, fiberglass, that has taken its share of criticism: “For every Btu of energy it takes to make this insulation, 12 Btu are saved every year,” says Tom Newton, manager of advertising and promotion for manufacturer CertainTeed.
Given that other insulation products deliver similar benefits, greenness is to some extent in the eye of the beholder. For instance, some contain a high percentage of recycled material; others come in new formulations that remove or replace ingredients known to be environmentally harmful. Then there are natural products, like cotton, that get major green points because they pose no risk to people with allergies or chemical sensitivities. So while there’s no set ranking system for what makes an insulation green, the good news is, wherever you want to touch down on the spectrum, there’s likely to be a product that meets your needs and budget. And that should make you feel warm all over.
The chief measure of insulation performance is R-value, which is derived from standardized tests that determine how well the material resists heat flow. The higher the resistance, the higher the R-value. Current standards in most parts of the U.S. call for at least R-13 exterior walls and R-38 ceilings (the latter being higher because of heat’s tendency to rise).
As a rule, the better a material performs, the more it costs, though some products are expensive simply because they occupy a tiny sliver of the market and can’t offer the economies that come with high-volume production. Following is a quick snapshot of the ingredients, performance, and cost of products in insulation’s two main camps, fiber and foam.
Made from shredded, fluffed-up newsprint containing 85 percent recycled material and 15 percent borate-based fire retardant (borates are environmentally safe mineral compounds that also stop mold and pests). Blown in dry or sprayed on wet—damp, really—it has a higher R-value than fiberglass and costs about the same.
Ever wonder what happens to old denim? Some of it gets turned into thick batts and is used to insulate walls and floors. Treated with the same borate fire retardant used in cellulose, shredded cotton is a popular low-chemical choice.
Some might wonder how this material merits mention alongside obviously greener goods, but manufacturers have given spun glass a higher recycled content (up to 40 percent) and have taken steps to reduce the acknowledged problem of airborne fibers. Some makers have started slipping their product inside a bag—a very effective treatment until it has to be cut to fit an odd-size cavity. Comes in batts or is chopped and blown into floor and wall cavities.
Made from recycled slag and mined basalt rock, mineral wool is naturally resistant to fire and pests and is highly sound absorbent. While it has been associated with the same potential airborne-fiber risk as fiberglass, one mineral wool product, a rigid-board foundation insulation, poses no such problem while providing a waterproof barrier.
Sheared from living creatures in the usual way, the cleaned fiber is formed into batts and lofty loose fill, then treated for moth- and mildew-proofing. Like cotton, wool tends to primarily be a health-related choice.
Made from magnesium oxide cement mixed with water, frothed with air, and pumped into cavities, it’s efficient, naturally fireproof, and resists mold and pests.
Polyicynene and polyurethane
Both of these foams are made with an oil-derived chemical, polyisocyanate, but does that necessarily erase any green tint? Maybe not, considering the energy these products save and the fact that their blowing agents—water for polyicynene, a non-ozone-depleting chemical for polyurethane—are environmentally benign. Different formulations produce two types, open-cell and closed-cell, the latter delivering a higher R-value and price.
In some formulations of polyurethane, petroleum-based ingredients are partially replaced with those from agricultural resources like soybean oil, sugar cane, and corn. Environmental benefits aside, oil’s recent price trajectory makes these products even more appealing. Available as sprayed foam and, in the case of soy-based, a rigid board.