When it comes to green building products, insulation stands out as a natural fit. After all, one of the main tenets of green building is increasing energy efficiency, and long before being green was in vogue, that's always been insulation's primary purpose. Now, with the rush toward all things green in the home building industry, insulation is one of the first categories builders look to when setting out to construct an environmentally friendly home.

"You could say all insulation is green, regardless of what it's made of," says Robin Bectel, director of communications for the North American Insulation Manufacturers Association, a trade association of fiberglass and mineral wool insulation manufacturers based in Alexandria, Va. "By definition, insulation saves energy."

Yet, as with all areas of green building products, insulation comes in different shades of green, based on its recycled content, whether it gives off any emissions, and the amount of energy it saves versus the amount of energy needed to produce it.

Fiberglass and cellulose manufacturers, which enjoy the overwhelming majority of residential sales in the United States--an estimated 80 percent to 90 percent--go tit-for-tat to differentiate themselves on those criteria. Fiberglass advocates, for instance, tout the fact that their product saves 12 times the amount of energy it takes to produce it in its first year of use.

But cellulose manufacturers, who make insulation out of ground-up recycled newspapers, say their product far outshines fiberglass. "Cellulose saves over 200 times the amount of energy it takes to make it," says Dan Lea, executive director of the Cellulose Insulation Manufacturers Association in Dayton, Ohio. Cellulose producers also like to point out that their product is made of up to 80 percent recycled content, compared with the 35 percent of recycled glass that goes into fiberglass insulation.

Of course, in terms of performance and ease of installation, each category has its dedicated followers. "We started using cellulose in 1992, when the spotted owl had a corner on the wood market, and a lot of people were using steel framing in their homes," says Craig Matteson, director of sales and technical services at ARC Insulation in Romeoville, Ill., which insulates approximately 800 homes a year. "We just found that in terms of performance, cellulose won hands-down when compared to conventional fiberglass insulation."

Fiberglass installers, of course, feel quite different, especially those who apply blown-in fiberglass, using the same kind of wet spray machine cellulose installers employ. "Unlike cellulose, spray-on fiberglass doesn't absorb the water you use to install it," says Jesse Horn of Horn Insulation in Rantoul, Ill., which insulates more than 500 homes a year. "Because fiberglass is lighter and less absorbent, once you spray it in there, the water tends to just drain right out." Horn's point is important, as any insulation can promote mold growth inside a wall if it holds moisture for prolonged periods.

While industry estimates peg other types of insulation as making up just 10 percent or less of the overall market, other "green" choices abound. For instance, The Green Building Products Directory, published by green watchdog group BuildingGreen, lists a full spectrum of insulation types including mineral wool; rigid polyiso panels; expanded polystyrene (EPS) foam; and foamed-in-place, cotton, and even soybean-based products, as green.

Atlanta-based Greenguard Environmental Institute, which advocates for a healthy indoor environment and measures the emissions of thousands of building products, has given its stamp of approval to insulation types ranging from fiberglass to mineral wool, EPS, and polyester.

Growing Concern
A concern over indoor air quality, and the hyper-focus on using low- or no-VOC-emitting building products, has spotlighted that area as a central facet of the green debate. Fiberglass manufacturers have grappled with the use of formaldehyde as a curing agent in their product (see "The Formaldehyde Factor," page 66), while cellulose producers are often questioned on whether their product introduces tiny fiber particles into the indoor air environment.

Cotton Contender
The debate has helped a relative newcomer, cotton insulation, enjoy increased interest--and sales--in the past two years. Manufactured from the leftover scraps of denim jeans and cotton shirts produced by the textile industry, cotton insulation provides high R-values, while borate additives help produce a Class A fire rating. The product also is particularly effective as a sound barrier in homes.

"Due to the irregular shape of the natural fibers, cotton has very good sound absorbtion," says Randy Robinson, regional sales manager for Inno-Therm Fiber Insulation. "A lot of people use it in quiet rooms, or media rooms, where they've got big speakers and sound they want to control."

Sherry Furr, a cotton insulation distributor and installer at InsulTechnologies, says one of cotton's primary benefits is its ease of installation. It comes in rolls, and can be cut with scissors, so pre-sized batts aren't an issue. "You don't need any special equipment or masks or gloves," Furr says. "And it doesn't have the particles that get into your skin like fiberglass, because it's just cotton." It should be noted, though, that some health experts question whether airborne cotton fibers can create a health risks, as well.

And of course cotton, like cellulose, is heavier than fiberglass. That means flat, attic applications reach a threshold that restricts more material from being used, due to loading limits. Cotton also tends to be about a third more expensive than fiberglass, which puts it in the same price range as cellulose. There are many shades of green when it comes to insulation, and the one you choose will depend on the application, cost, and homeowners' preference.

--BUILDING PRODUCTS

The Formaldehyde Factor
When formaldehyde was declared a known human carcinogen by the International Agency for Research on Cancer in 2004, the building industry, and manufacturers of fiberglass insulation in particular, took notice. The chemical, which occurs naturally in items from apples to seawater, is used as a binding agent in the curing process of fiberglass batts, acting as the "glue" that holds fiberglass fibers together.

Due to those concerns, several fiberglass manufacturers are making formaldehyde-free products. For instance, Johns Manville started producing formaldehyde-free fiberglass batts in 2002, using an acrylic binder instead.

"That decision stemmed out of a concern from customers that they were installing and using something that, at the time, was a probable human carcinogen," says Johns Manville spokesman Cory Ziskind. "The philosophy was that especially as homes are being built tighter and more energy efficient, the products that make them more energy efficient shouldn't contribute to poor indoor air quality."

Yet, many fiberglass insulation products that still contain formaldehyde are deemed "green," nonetheless. The reason why, experts say, is because formaldehyde emissions from fiberglass insulation are considered nominal, with much of the chemical baking out of the material during production. Take Owens Corning's fiberglass batts, which contain formaldehyde but have earned the Greenguard Environmental Institute's seal of approval for indoor air quality.

"Obviously, formaldehyde in high concentrations is a concern," says Gale Tedhams, head of residential insulation at Owens Corning. "But we don't think there's an issue with formaldehyde in our product, because it's used in a very, very small amount. We think our Greenguard certification is really the best way to evaluate that."

--J.B.

Guardian Fiberglass

Guardian Fiberglass

Guardian Fiberglass. This firm has received Greenguard certification for children and schools on numerous products, including its AsureR, UltraFitDS, and AtticGuard Loosefill offerings, meeting stringent standards for indoor air quality. Its PerfectFill insulation is a new fiberglass insulation that uses netting and formaldehyde-free white blowing wool in wall, floor, and ceiling cavities. 800-569-4262. www.guardianbp.com.

Thermafiber

Thermafiber

Thermafiber. This rock wool insulation contains 80 percent recycled slag, a by-product of steel production. Slag and other rocks are melted at 2,600 degrees F to fiberize the material. The manufacturer says starting from rock makes the product inherently fire resistant and more dense than fiberglass insulation, resulting in a higher R-value per inch. 888-834-2371. www.thermafiber.com.

Johns Manville

Johns Manville

Johns Manville. The Spider Custom Insulation System is a formaldehyde-free, spray-in fiberglass insulation that eliminates all gaps and voids in wall cavities where energy can escape, the firm says. Spider is made from inorganic fiberglass that naturally does not support mold growth. It's composed of 20 percent post-consumer and 5 percent post-industrial recycled glass content. 800-654-3103. www.johnsmanville.com.

CertainTeed

CertainTeed

CertainTeed. Optima fiberglass insulation is a blow-in blanket system for new construction closed-cavity applications such as sidewalls, cathedral ceilings, and floors. It's comprised of a non-woven fabric facing behind which the insulation is blown dry, without additives or moisture. The product has Greenguard certification for low emissions, and contains 20 percent recycled content. 800-233-8990. www.certainteed.com.

InnoTherm

InnoTherm

InnoTherm. This firm produces cotton insulation pads and rolls, using scraps from cotton shirt and denim producers. It offers R-11, R-13, and R-19 options. The firm says its products contain no melamine or phenolic resins, and can be installed without safety precautions. The firm claims its fiber insulation is permeated with a safe, deep-absorbing fire retardant that does not powder out, increasing safety and durability. 828-466-1147. www.innotherm.com.

Owens Corning

Owens Corning

Owens Corning. The Propink Complete blown-in wall system is designed for enclosed cavities, including walls and ceilings, and is Greenguard certified for children and schools. The manufacturer says it will not settle, rot, or decay, enabling consistent R-values of R-15 in 2x4 construction and R-23 in 2x6 construction. A dry system, it doesn't add moisture to the wall or ceiling cavity. 800-438-7465. www.owenscorning.com.

US GreenFiber

US GreenFiber

US GreenFiber. The firm says its Cocoon cellulose insulation line contains 80 percent recycled paper and provides outstanding resistance to heat flow for thermal applications, noise suppression for acoustical treatments, and added fire resistance for fire-rated assemblies. The company supports energy conservation programs focused on environmental responsibility. 800-228-0024. www.us-gf.com.

InsulCot

InsulCot

InsulCot. Claiming to be the first patented cotton insulation, InsulCot insulation hit the market more than 15 years ago. It carries a Class A fire rating, is non-toxic, and uses no boric acid. The manufacturer says its product saves up to 30 percent more energy than fiberglass, and is biodegradable. It is manufactured from 75 percent recycled cotton and 25 percent polyester. 806-777-2811. www.insulcot.com.

Nu-Wool

Nu-Wool

Nu-Wool. Engineered cellulose insulation contains 85 percent recycled newsprint, an attribute the manufacturer says makes it one of the "greenest" products available. Nu-Wool processes more than 150 tons of recycled paper each business day, or the equivalent of 2,550 trees. 800-748-0128. www.nuwool.com.