Insulating Green with Blue Jeans

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by Planning Technician Carol Borck

Heating and cooling account for about 50% to 70% of your home's energy bills. Adequate, properly installed insulation is key to controlling both energy loss and consumption in your home. Insulation is designed to resist the flow of heat; it keeps warmth inside during the winter and heat out in the summer.

When I hear the word insulation, I immediately picture "the pink stuff," i.e., traditional fiberglass insulation. Indeed, fiberglass, or "fibrous glass dust," is the most commonly used type of insulation. Composed of man-made mineral fibers, fiberglass is made from molten sand and in-organic materials. While fiberglass insulation is an effective insulator, durable, and usually contains at least 20% recycled glass, it is a material that is hazardous to install and remove and contains off-gassing carcinogenic resins.

Cotton battingWhat many homeowners don't know is that there are numerous alternative materials and products available for building insulation, including cellulose, mineral wool, polyurethane and cement-based foams, and cotton. At a recent green-building lecture, I discovered a type of insulation that really intrigued me: recycled denim. Recycled denim? I wondered what exactly that meant! Was it really old, discarded blue jeans finely shredded and molded to fit into the walls of a house? Upon researching the topic further, I learned not only what "recycled" denim means, but also the merits of this exciting product.

There are a few different manufacturers of recycled denim insulation (easily found via internet), and their products utilize 100% post-industrial denim and cotton fibers from denim manufacturing facilities. What this means is that the scraps and remnants generated in making denim clothing are the fibers that go into the insulation (and not the faded jeans you donated to charity last year). Once collected, the denim trimmings are cleaned, cut, and "re-fiberized" with the end-product being formed into cotton batting. About 85% of the batts consist of these natural recycled fibers; polyester fibers used for bonding fill out the remaining 15% of the content. In addition to keeping these cast-off materials out of the landfill, this natural fiber insulation requires a very minimal amount of energy to produce, unlike fiberglass and foam insulations.

Batt, close-upHealth & Safety

Natural cotton fiber insulation is touchable, it does not irritate your skin, and can be installed without protective respiratory gear or clothing. Compared to traditional insulation, this cotton fiber insulation contains no chemical irritants, no melamine or phenoloic resins (no formaldehyde), and therefore poses no possibility of volatile organic compound (VOC) off-gassing into your home; there are no carcinogenic warning labels required for this product.

To resist mold, mildew, bacteria, and fungi growth, the natural fiber insulation is treated with a non-toxic borate solution. Borates are not found to be a risk to human health, have many applications, and are found in numerous everyday products. The borate solution in the insulation also serves to act as a very good fire retardant and pest inhibitor.

Insulating Performance

Insulation is rated using an "R-value." The R-value refers to "thermal resistance" and is a measure of the product's ability to resist heat transfer; the higher the R-value, the more effective the insulation. R-values are usually listed as R-value per inch thickness of insulation material. For any thickness, the total R-value is computed by multiplying the rated R per inch by the thickness of the insulation. Typical ratings include:

Loose Fill Fiberglass
Loose Fill Cellulose
Fiberglass Batts
Extruded Polystyrene
Recycled Denim Fiber
R-2.3 to R-2.8 per inch
R-3.1 to R-3.7 per inch
R-3.1 to R-4.2 per inch
R-5.0 per inch
R-3.45 per inch

Recycled denim insulation is commonly available in R-11, R-13, and R-19 batts. It is appropriate for both interior/exterior wall and ceiling applications and can be installed in either wood or metal framing cavities. Attic insulation is recommended to be at R-38, while R-13 would be acceptable for exterior walls.

Natural fiber insulation also provides excellent acoustical benefits, reducing sound transmission between rooms within the house and from exterior sources.

Installation Importance

As with any insulation product, proper sizing and installation cannot be stressed enough to maintain thermal performance. Gaps, compression and misalignment of the insulation must be avoided. The insulation should fill the entire framing cavity without being compressed and be cut around electrical outlets and fit over wires and plumbing pipes.

Look for a licensed contractor with strong references, who has been installing for a time, and is continually trained on new techniques and products. Some insulation contractors specialize in installing one type of insulation, others may install several types. Ask questions, obtain estimates, and remember that quality insulation and installation, regardless of material type, is a long-term investment and will provide you with energy savings year after year.

Environmental Benefits

  • Consists of 85% recycled cotton content
  • Cotton is a renewable resource
  • Potentially recyclable at "end of life"
  • Uses less energy to produce
  • Does not contain harmful chemicals/resins
  • Insulates as effectively as traditional insulation

Disclaimer: The products pictured in this article do not constitute an endorsement, approval, or recommendation of the product by the Town of Portola Valley. These product images are provided only for informational purposes and as visual examples.

If you have a green building topic you would like explored further in an article on this web page, please feel free to provide me with your suggestions at cborck@portolavalley.net or via telephone.