How Denim Insulation Works

Humans have a long and storied history with cotton. Before we transform a pair of jeans into insulation, let's figure out how denim is made.

Everything begins with cottonseed, which germinates into a small plant that sends up creamy, white flowers about three months after planting. After changing color, the flowers wither and die, leaving green pods known as cotton bolls. This is where it starts getting hairy. Inside the boll, a tangle of fibers grows around the forming seeds. These fibers are where T-shirts, briefs and jeans begin their lives. The warm sun causes the fibers to expand until, finally, they rupture the boll and burst forth like popcorn erupting in hot oil.

During harvesting, cotton-picking machines remove the seed cotton from the plant. A process known as ginning separates the seeds from the fibers and results in bales that make their way to textile mills specializing in yarn manufacturing. This involves raking debris from the fibers, straightening the fibers into a continuous strand called sliver and then spinning the sliver into yarn. Looms weave cotton yarns into fabrics by interlacing lengthwise strands known as the warp with crosswise strands known as the filling. These fabrics then arrive at finishing plants, where they are preshrunk, dyed and transformed into denim. Finally, denim manufacturers produce the clothing we buy.

After a few months or years, most people are ready to retire their old jeans for something spiffier. This is where denim recycling comes in (more on those logistics later). First, workers must separate the denim from other materials and then remove any zippers, buttons and hardware from the fabric, in the same way that you remove staples from paper before you shred it. Next, it heads for large shredders that grind the material to pieces. The chewed-up denim moves to a baler, which produces 1,000-pound (454-kilogram) bales. Trucks then haul the bales to a second processor that, basically, unweaves the denim, returning the textile to its original fiber state.

This is the raw material, which looks a bit like blue cotton candy, that arrives at Bonded Logic. Once there, workers treat the fabric with a borate solution so the insulation won't burn and so it will repel mold and mildew. Next, they mix the material with another fiber and bond everything together in a large oven. Finally, they press the material into 2-inch (5-centimeter) thick rolls and cut the product into its shipping size.

Up next, we'll pit blue against pink -- denim against fiberglass -- to see if a house decked out in blue jeans can really achieve thermal efficiency.

Builders have been stuffing homes and businesses with fiberglass insulation for years because it's fairly easy to manufacture and works well. It consists of a fine matrix of flexible glass fibers that creates thousands of microscopic cells. These tiny pockets trap air and keep it from circulating, which reduces convection and heat transfer. However, the small glass fibers can stick into the skin and cause irritation. They can also get into the eyes and into the lungs if inhaled. Some reports, such as the 1994 Annual Report on Carcinogens, have labeled fiberglass as "possibly carcinogenic," prompting manufacturers to apply related warnings to their products.

Denim insulation carries no such warnings. It doesn't cause itching or irritation and can be installed without gloves, safety goggles or a dust mask (although DIY types and professionals may still want to wear a mask while cutting the batting). And it's safe for the long haul. Unlike some materials that off-gas toxic vapors or volatile organic compounds as they sit in your home, denim insulation sits inertly in your walls and floors, blocking the flow of heat without releasing harmful chemicals or irritants.

But does it work? Does it actually compete with the pink fiberglass made famous by the cartoon panther of the same color? Let's do a head-to-head comparison of the three most important functional attributes of building insulation -- R-value, acoustic performance and fire resistance.

R-value measures an insulation's resistance to heat flow. If a material has a high R-value, it has a greater insulating effect. Fiberglass batting with a thickness of 3.5 inches (8.9 centimeters) delivers an R-value of 10.90 [source: Nave]. Increase the thickness to 6 inches (15 centimeters), and the R-value of fiberglass soars to 18.80 [source: Nave]. The same thicknesses of denim insulation deliver R-values of 13 and 21, respectively [source: Bonded Logic ]. Score one for denim.

See how denim insulation fares on acoustics and fire resistance next.

Acoustics: Contractors and builders often mention the noise reduction coefficient, or NRC, when discussing the acoustic performance of insulation. NRC values commonly range from 0 (reflects all sound) to 1 (absorbs all sound), but it's possible to have an NRC above 1, depending on the material's shape or surface area. Fiberglass batting with a thickness of 3.5 inches (8.9 centimeters) delivers an NRC of 0.90 to 0.95 [source: NRCratings]. The same thickness of denim scores 1.15, which means blue beats pink again when it comes to blocking airborne sound transmission [source: Bonded Logic].

Fire resistance: In the U.S., the fire resistance of materials is generally rated as Class A, B or C, according to the applicable standards published by both Underwriters Laboratories and ASTM International. Class A denotes the ability of a substance to withstand severe exposure to fire originating from sources outside the building. Both unfaced fiberglass and denim insulation have received Class A fire ratings. It should be noted, however, that the brown paper (or facing) on some fiberglass batting is flammable.

So, denim can hold its own against the usual suspects in terms of meeting the basic functional requirements of insulation. Of course, the economic benefits of using denim insulation aren't immediately apparent. The initial costs of denim far exceed those of fiberglass. According to the Home Depot Web site, UltraTouch denim insulation retails for $6 per roll (16 inches by 48 inches or 41 centimeters by 122 centimeters), while Owens Corning fiberglass insulation costs $3.15 for the same size roll. That works out to about $1.12 per square foot for denim insulation and about 60 cents per square foot for fiberglass.

Denim insulation is easy to install, however, and that can save time and money. We'll tackle installation on the next page.

Before you can install denim insulation, you have to get your hands on it. Unlike the fiberglass variety you can pick up at your local home improvement store, UltraTouch and other cotton insulation products were not readily available in retail outlets as of November 2011. Of course, if you head online, you can find a local distributor or buy it directly.

Once you have a supply of denim insulation at your house, you can get started with installation. You won't need your utility knife because the UltraTouch rolls come perforated to accommodate framing cavities of different sizes. You'll need a tape measure and, if your local building code calls for it, a material to provide a vapor barrier, as UltraTouch batts only come unfaced. Bonded Logic recommends the use of a semipermeable barrier with its denim insulation.

There are no limitations to where you can install UltraTouch. It's effective in interior and exterior walls, as well as most ceiling applications, and it can be used in either wood or metal framing cavities. Before you get started, though, you need to make sure the insulation has fully rebounded, or expanded back to its original thickness. This is necessary because the material gets compressed to make it easier to package. To accelerate the rebounding process, simply give each roll of denim insulation a good shake and let it sit for a while. Depending on climate and environmental conditions, full rebound may take several days.

After that, installation is quick and easy. UltraTouch relies on a friction fit -- each piece of insulation should be approximately 0.5 inches (1.3 centimeters) wider and longer than the actual cavity, enabling the material to fit securely without stapling. Bonded Logic manufactures UltraTouch to fit standard framing cavities (16 inches and 24 inches on center or 41 centimeters and 61 centimeters) with no additional sizing required. If you encounter an off-size cavity, the perforated rolls may work to create the proper fit. You can also use perforated rolls to make small pieces that fit around vent lines and electrical boxes. Also apply leftovers to small openings around windows and doors. Finally, if a vapor barrier is required, install it on the living-area side of the wall after you've installed the insulation.

With that, you'll be done -- unless you want to help others get their supply of denim insulation. Turn the page to learn more about denim recycling.

Levi Strauss & Co. donated 200,000 pairs of jeans to help insulate the California Academy of Sciences in San Francisco. That's a lot of blue to make a green building, which is why installing denim insulation is just the beginning. Getting involved in a denim recycling program keeps clothing out of landfills and supplies companies such as Bonded Logic with the raw material they need to make denim insulation even more accessible to the residential and commercial markets.

One notable program is "Cotton. From Blue to Green," launched in 2006 by Cotton Incorporated. The program targets college students, educating them about the renewable attributes of denim and encouraging them to donate their old jeans to the cause. Students can drop their jeans in campus collection boxes or at participating retailers, such as G by GUESS specialty stores or American Eagle Outfitters. The donated denim goes directly to Bonded Logic, which then transforms it into UltraTouch insulation. Through 2010, the program had collected more than 600,000 pairs of jeans, leading to the production of 1,485,000 square feet (138,000 square meters) of denim insulation [source: Cotton. From Blue to Green].

"Cotton. From Blue to Green" also allows consumers to mail in recycled denim. To get involved in this program, pack your old denim in a box, download and print a mailing label from the organization's Web site (www.cottonfrombluetogreen.org) and then ship it to Bonded Logic via the U.S. Postal Service, FedEx or UPS. Make sure your box contains no more than 100 pieces of denim and be sure to bring your wallet to cover the shipping costs.

If you're not too keen on seeing a good pair of jeans shredded into pieces to make insulation, remember tried-and-true options, such as donating to local charities. Levi Strauss & Co. has formed a partnership with Goodwill in the United States to encourage consumers to donate their old jeans instead of tossing them in landfills. To that end, the famed maker of blue jeans and other denim clothing now sews a care tag on every garment it sells. The care tag encourages consumers to wash their jeans in cold water, line dry them when possible and donate them to Goodwill when they're ready to move on to a new pair of 501s.

Either way, donation or insulation, it's easier than ever to go green with your blue.