Cotton insulation is manufactured from recycled clothing and remnants from the textile industry. It is often called denim insulation because much of the raw product is sourced from old blue jeans made into cotton batts and loose-fill blow-in attic insulation.
Where to Use Cotton Insulation
Cotton insulation is used in the same locations as traditional insulation products like fiberglass and cellulose. The batts are manufactured to fit standard 2 x 4 and 2 x 6 framing and also fit in rafter and floor joist cavities.
Cotton batts are heavy, so rafters and joist installations may require strapping or netting to hold them in place. This is essential for crawl space insulation–where no drywall will be applied–and most other non-vertical locations.
Recycled cotton is made into loose-fill insulation for attic floor installation. Its R-value of R-3.5 per inch is higher than loose-fill fiberglass insulation and matches cellulose insulation. Cotton loose-fill can also be blown into new construction walls, rafters, and joist spaces if netting is used for retention. It can be used in retrofit applications without removing the drywall. Small holes are cut into each stud cavity to allow blowing of the product–then patched and painted.
Cotton insulation batts were popular in the US from around 1900 to 1950. Even Sears Roebuck sold faced cotton insulation. Cheaper materials like fiberglass began dominating the market. Environmental and health concerns caused the resurgence of cotton. The market share is still relatively small, but more home buyers are demanding healthier choices like cotton and sheep wool insulation.
Cotton insulation batts have an R-value of R-3.5 – R-3.7 per inch–about the same as fiberglass batts.
Cotton insulation is made from over 80% recycled materials. Making a very sustainable product. It is treated with borax fire retardant. Borax has the added advantage of repelling mold, mildew, and pests. Cotton contains no formaldehyde or lung-irritating fibers.
Cotton insulation can be recycled again at the end of its insulation life. Most other types of insulation go to landfills when they are removed. Growing cotton and the textile industry use more resources than many other products so recycling it into eco-friendly insulation helps to balance the scale somewhat.
Easy Safe Installation
Cotton batts are safe and easy to install without protective equipment except a mask to protect from any residual dust. Batts are manufactured to standard sizes, 92 ½” for 8’ wall cavities, or in rolls. Installation can be done by contractors or as a DIY project.
Loose-fill cotton is blown into attics and walls with the same equipment as cellulose or fiberglass. Using a mask is a good safety precaution but it is not as dusty as cellulose or as itchy as fiberglass.
Cotton insulation reduces sound by about 30% more than fiberglass. It keeps the house quieter and can be used in interior walls to keep bedrooms and bathrooms quiet and prevent sound from escaping home theaters.
Cotton insulation is fully recyclable even if it gets soaked. It just needs to be dried out and remade into insulation.
Cost and availability are the biggest disadvantages of using cotton batt insulation, but there are a few others to consider.
Cotton insulation costs an average of $1.00 per square foot depending on thickness and R-value. Fiberglass batts cost around half that.
Cotton insulation batts can be inconsistent. Sold as fitting standard wall cavities, they can be too wide or too narrow. Cotton is much more dense than fiberglass and is difficult to stretch to fill spaces. The batts or rolls are also more difficult to cut straight.
Like fiberglass batts, cotton insulation is compressed and tightly wrapped to make shipping more convenient. Unlike fiberglass batts, cotton batts do not always regain their intended size–losing some insulation value.
Cotton wall insulation requires a vapor barrier like 6 mil poly because it readily absorbs and holds moisture. If wet enough, it becomes heavy and can slump inside the wall leaving uninsulated voids. Cotton insulation is unavailable as a faced product.
Cotton insulation is often difficult to find. Even large home improvement outlets rarely have it in stock. It may have to be ordered in pallet-sized lots. Special orders take longer to arrive and unused product is usually non-returnable.