Although many insulation products claim to be green, few are exceptionally so. However, some genuinely innovative insulations that contain renewable or recycled content are making their way into our homes.

Intro to Insulation

Insulation slows heated or conditioned air from escaping the building envelope and keeps ambient heat or cold from entering it. It also serves to absorb sound and dampen vibration through building components.

Insulation comes in an array of shapes, sizes, and materials. Composed of products ranging from glass fiber to wood pulp, insulation can be purchased as standard-sized batts, blankets, wraps, boards, sheets, dry loose-fill, or liquid aerosol foam sprays.

Residential insulation is rated by its thermal resistance, or R-value. Based on a ratio of thermal variance and heat transfer through the insulating material, R-values are generally calculated per inch of material thickness; higher R-values indicate greater insulating effectiveness. Its performance also depends on the material’s composition and density as well as its ability to resist air infiltration and humidity. A project’s site conditions, such as its installation and the construction quality of the building envelope, also affect performance. R-values range from around R-1 per inch for solid wood to R-19 for a typical 5.5-inch-thick glass-fiber batt.

While many insulation materials are recyclable, several natural, recycled, and often unconventional products have sparked interest among environmentally minded builders. These products not only make good use of materials that would otherwise go to landfills, but many are also composed of nontoxic, nonallergenic materials that contain no harmful processing chemicals, such as formaldehyde or volatile organic compounds (VOCs). “There are no warning labels on our packaging,” says Sean Desmond, marketing director of Bonded Logic, which manufactures UltraTouch recycled cotton denim insulation.

Designers and builders looking for environmentally sensitive insulation now have an array of choices that are reducing the tons of waste sent to landfills every day.

Expanded Cork Insulation Board

Cork insulation was developed in the U.S. in the late 1800s and was popular until the introduction of more competitively priced and readily available insulation materials, such as mineral wool and glass fiber. But thanks to its environmental attributes, it is making a comeback.

While some products reconstitute cork particles into an adhesive matrix, cork insulation is an all-natural material. Manufacturers such as Amorim Isolamentos adhere to the traditional manufacturing process by first grinding the material into uniform-size granules, and then steam heating them to expand and release a natural resin binder. Drawbacks to cork insulation, which is sourced primarily from Portugal, include higher initial cost and nonstandard stud and joist cavity sizes. On the upside, cork possesses immense soundproofing capabilities, contains no toxins, and is entirely recyclable. Sold in 12- and 24-inch widths, cork insulation’s R-value ranges from R-3.6 to R-4.0 per inch.

Cotton Denim Insulation

The next time you toss out a pair of worn blue jeans, consider how their comfort and durability might keep homes comfortable as well. Manufacturers are now repurposing denim waste and remnants into batt and blanket insulation. The raw materials come from post-consumer content or denim manufacturing scrap shredded down to its individual fibers, which provide effective sound absorption and thermal performance. Up to 80 percent of the insulation content is natural cotton with additional fibers from sources such as synthetic fabrics and carpet.

Denim insulation is sold in standard- and nonstandard-size batts and blankets, including friction-fit widths for both metal and wood framing cavities. For the case of UltraTouch’s product, the denim’s thermal performance capacity is “almost identical to fiberglass” insulation, Desmond says. Denim’s R-value is about R-3.5 to R-4 per inch of thickness.

Polyester Batt Insulation

If you prefer more synthetic materials, recycled polyester insulation has several environmentally sustainable advantages. Sourced from materials such as recycled drinking water bottles and post-consumer polyester plastic products, it typically contains zero VOCs or harmful chemicals such as formaldehyde. The insulation requires minimal processing, is recyclable in its entirety, and also offers excellent compression recovery with virtually no product degradation over time.

Polyester batts can be soft and pliable with a thermally bonded, nonwoven, nonirritating, uniform composition, making them easy to handle and install. Batts are rated at approximately R-3.7 per inch of thickness and sized to friction-fit into standard-dimension stud and joist cavities.

Sheep Wool Insulation

Everyone knows that animal wool makes warm clothing. This natural fiber has also found new use as a sustainable, recyclable home insulation. One manufacturer, Jiangsu KPS Wool Timbering Science Technology Co., produces pure sheep wool insulation that is free of processing chemicals and VOCs, and will not cause skin allergies or itching.

Initially developed for building panels for commercial and public utility projects, sheep wool insulation meets U.S. residential construction and fire code standards. It is available in blankets and standard insulation batt sizes with a rating of R-3.2 per inch.

Although no federal regulations mandate which insulation material designers should specify, cities and states with sustainable building programs are considering implementing environmental standards for materials, including insulation, in public works projects. Beyond material composition, industry groups such as the Safer Insulation Solution are also working to reduce hazards associated with conventional insulation materials, such as the toxic flame-retardant additives in plastic foam insulation.

The range of sustainable insulation options now on the market—with more options likely on the horizon—demonstrate that materials once regarded as waste can now keep us warm and healthy in our homes.