Adding wall insulation is one way to create a tight house envelope. Leaving wall cavities open and free of insulation was commonplace prior to the mid-20th century. Now, it’s a given that the walls of homes in nearly every climate will receive some type of insulation. Invariably, that insulation is fiberglass, cellulose, or foam.
But gaining traction is a market for alternative insulation materials. One very green and innovative alternative comes from our closets: denim. Denim insulation is easy to work with and recyclable,
What Denim Insulation Is
Similar to blown-in cellulose insulation, most denim insulation is Class A fire-rated as it is treated with a borate-based flame retardant. Plus, the same solution that slows flames helps to prevent the growth of fungi and bacteria.
Denim insulation is rated in many of the same R-values as fiberglass insulation, such as R-13 (for two-by-four stud wall assemblies) and thicker R-19 insulation (for two-by-six wall assemblies).
What Is R-value?
R-value refers to thermal resistance, or the ability of a material to resist thermal conditions—cold or heat. The higher the R-value number, the better the material is at limiting thermal conductivity.
Denim insulation is often used instead of fiberglass or other types of insulation because it is easy to handle, environmentally friendly, and acoustically efficient.
For homeowners who balk at insulating their homes due to the difficult nature of fiberglass, denim insulation can be the perfect incentive to get the job done.
How Denim Insulation Is Made
- After old denim is no longer used, it is sent to a recycling facility.
- Workers remove all extraneous materials such as zippers and buttons.
- Mechanical shredders grind up the denim into small pieces.
- Pieces are packed into large bales.
- Bales are sent to another processor, which further shreds the denim into a fibrous state.
- Fibers are treated with borate flame retardant.
- Treated fibers are pressed into large mats.
- Large mats are cut into sizes that will fit into wall or floor cavities.
Pros of Using Denim Insulation
Easy to Handle
Denim insulation is just as soft and easy to handle as its source material, blue jeans. There is no need to suit up with long sleeves, gloves, and long pants, as you would with fiberglass insulation. You can handle denim insulation with your bare hands.
Better For Respiration
Denim insulation does not release irritant fibers into the air like fiberglass insulation does. While it is recommended that you wear a dust mask when working with denim insulation, that's about all you need: a basic dust mask. For fiberglass insulation, it’s always best to wear a tight-fitting half-face respirator or at least a N95 mask.
Denim insulation is a 100-percent post-consumer recycled material. All of the materials were previously used.
Not only does denim insulation use recycled materials, denim insulation itself can be recycled, post-use. Few, if any, other types of insulation can claim this. Unless it is in pristine condition, used fiberglass insulation cannot be reused. It must be landfilled.
Cons of Using Denim Insulation
Denim insulation is more expensive than fiberglass insulation; on average, it costs about 10 percent more than fiberglass. One pallet of R-13 denim insulation, covering a total of 16,740 square inches, costs about $824. One pallet of comparably sized R-13 fiberglass insulation costs about $750.
Harder to Cut
Because denim insulation comes in dense mats, it can be more difficult to cut than fiberglass insulation.
Less Malleable (Sometimes)
One of the benefits of using fiberglass insulation is that it is very malleable. If you need to stretch the insulation just another inch or two, it's possible to do so. Or you can grab a hunk of discarded fiberglass and force it into an empty spot easily.
But denim insulation can be a tight mat that does not stretch as easily and does not have the same fluffy properties as fiberglass insulation. You can pull off hunks, but just not as easily as it is with fiberglass insulation. Now, though, some denim insulation is actually available in rolls, which is very similar to fiberglass insulation in installation.
Sometimes Difficult to Find
It is becoming ever easier to find denim insulation in home centers. But you can't always count on it. Even when you do find denim insulation, it may be in limited quantities or by special order only. Or the opposite might be the case: You may be required to order it in large quantities only.
Islam, Shafiqul, et al. "Microstructure and performance characteristics of acoustic insulation materials from post-consumer recycled denim fabrics." Journal of Industrial Textiles (2020): 1528083720940746.
Asdrubali, Francesco, Francesco D'Alessandro, and Samuele Schiavoni. "A review of unconventional sustainable building insulation materials." Sustainable Materials and Technologies 4 (2015): 1-17.