What is Denim Insulation?

Denim insulation is old blue jeans turned into house insulation. Blue jean insulation occupies a small but growing niche and is made from recycled material that consumers can recycle again. It takes approximately 500 pairs of recycled blue jeans to insulate a new home.

Denim Insulation

More and more homeowners are replacing insulation materials like fiberglass batts and rigid or sprayed foam with more ecologically sound, greener products. Denim batt insulation fills that void – but at a cost.

How is Denim Insulation Made?

To make denim batts, manufacturers send old jeans and compatible cotton products to recycling plants, where they remove zippers, buttons, and contaminants. Then they shred the jeans into small pieces and package them into thousand-pound bales.

The bales are taken to another processing plant, where the fabric is shredded further. The resulting product is closer to the original state of cotton balls and looks like blue cotton candy.

Once it arrives at the manufacturing plant, it’s treated with boric acid to make the material fire retardant and pest, mold, and mildew resistant. It’s then heated to bond the fibers together and pressed into large mats that are cut to size.

Denim Insulation Pros

Denim batt insulation has around the same R-value as fiberglass batts–R-3.5 per inch. The batts come in standard sizes to fit standard 2 x 4 and 2 x 6 stud-framed walls with R-values ranging from R-10 to R-20.

Denim Insulation is Eco-Friendly

Denim insulation is close to 100% recycled. The majority of the inputs come from worn blue jeans. 

Denim Batts are Safer to Install

Denim batts don’t contain formaldehyde or small fibers that humans can breathe in–like fiberglass and mineral wool insulation do. There are no Volatile Organic Compounds (VOC) in jean insulation either.

Most people can install denim insulation without gloves, masks, or special clothing. It contains no chemicals or irritating fibers. It may contain a small amount of dust left over from the manufacturing process, so anyone with sensitive skin or breathing problems should take the appropriate precautions.

Denim Batt Insulation is Fire Retardant

Denim insulation is a class A fire retardant. It’s treated with boric acid to reduce flame spread. Borate is the same fire retardant product used in cellulose insulation.

Denim Batts are Pest and Mildew Resistant

Boric acid also acts to repel insects and rodents. Borate-treated insulation ensures that insects and rodents will not take up residence in or eat denim batt insulation. Unless denim becomes wet and stays wet for some time, the boric acid also restricts mildew and mold growth.

Denim Provides Better Soundproofing

Denim batt insulation has an STC rating of 52 compared to fiberglass STC of 46. The chart below shows a significant improvement from STC 45 to STC 50. Denim can provide up to 30% more soundproofing than fiberglass, making it a good choice for multi-family buildings or for keeping the sound inside home theaters.

STCWhat can be heard at this level
25Soft speech can be heard and understood
30Normal speech can be heard and understood
35Loud speech can be heard and understood
40Loud speech can be heard, but not understood
45The threshold at which privacy begins
50Loud sounds can be heard, but are very faint
60+At this level, good soundproofing begins. Neighbors generally are not disturbed by very loud speech from inside.

Blue Jean Insulation is Recyclable – Again

Denim may be the only insulation that is available to recycle after use. Consumers can reuse the insulation batts or send them to a recycling plant.

Denim Batts Cons

As with most products, denim insulation isn’t perfect. Here are some of the cons.

Denim Costs

Denim batts cost at least 10% more than the equivalent fiberglass batt. In some cases, denim costs twice as much as fiberglass. The discrepancy is due to availability, quantities, and raw material supply.

Blue jean insulation is a fairly new product. There are not a lot of manufacturers, and some have shut down operations due to a lack of raw materials.

Denim Insulation is More Difficult to Fit

Insulation batts work best when they fit snugly into the stud cavity. Fiberglass batts are easy to stretch an inch if needed or manipulate around pipes and wires. Denim is a tight mat that is hard to stretch. It is also more difficult to add a piece of denim where required.

Like most types of insulation, denim traps air inside the material to provide the R-value. Compressing the batts too much squeezes out the air–reducing performance.

Denim Is Harder to Cut

Denim batts are denser than fiberglass, making them more difficult to cut through and harder to achieve a straight cut. Heavy-duty shears or a utility knife with a heavy wide long blade (preferably at least 4”) usually work best. 

Denim Requires a Vapor Barrier

Denim is good at absorbing and holding moisture. If denim batts absorb too much moisture, the weight can cause them to slump inside the wall cavity. Wet insulation loses its insulation value. When used as batt insulation, denim needs a vapor barrier such as 6 mil poly to keep it dry, which adds to the cost and time.

There’s Limited Quantities

Not all building centers carry blue-jean insulation. If they do, it may be the wrong size, or they may not have enough. Quite often, you can only get it by special order, which can lead to long waits and may require minimum quantities.

Denim insulation comes in wall and floor batts. Denim blown-in attic insulation is not available at this time. HVAC duct liner is available, but finding it may be a problem.

Why Denim Jean Insulation Is Hard to Find

Denim jeans produce approximately 2.16 million tons of waste every year. Few countries possess the infrastructure or political will to collect and separate old clothing. Even the European Union–which has a system in place–only collects 35% – 50% for recycling.

Lack of collection, separating, and processing facilities chokes off the supply of denim insulation raw materials, which means fewer manufacturing plants, less competition, and higher priced products.