Does Cotton Insulate?

Sources of Cotton Insulation

• Cotton insulation is produced by processing detritus and scrap produced by the denim wear industry along with other scrap fabric. In addition to recycling easily available materials, using scrap is better because current cotton production relies heavily on pesticides. Because of the high percentage of denim fibers, cotton insulation retains the classic blue-jeans color. Finished insulation has cotton contents of between 85 and 100 percent.

Production of Cotton Insulation

• Shredded fabric is treated with fire-retardant, usually boron-based compounds but is not bleached or treated with other chemicals. Fire-retardant abilities compare favorably with other insulations of similar thicknesses, especially fiberglass. Batts are formed slightly outsized, so that they can be held between rafters or floor stringers by friction. Batts are customarily produced without an attached vapor barrier. Some manufacturers use a formaldehyde-based wood glue to shape batts; others omit formaldehyde.

Advantages of Cotton Insulation

• Cotton insulation matches or compares favorably with other insulations in terms of R (resistance to heat-flow) values. Breathable, like sheep wool, cotton insulation dissipates moisture without deterioration; note that neither is recommended for chronically wet situations. Low in chemical content, cotton insulation is particularly distinguished by itch-free handling and installation. Manufacturers tout cotton insulation as being especially child friendly.

Disadvantages of Cotton Insulation

• The main obstacles to using cotton insulation appear to be economic. The U.S. Department of Energy notes that, by the square foot, cotton insulation can cost 10 to 15 percent more than conventional fiberglass; other estimates run as high as twice more. A small number of manufacturers and suppliers also keep cotton use from spreading rapidly. Do-it-yourselfers may well find the batts heavier than comparable-size fiberglass ones. Local building codes will address the issue of installing a separate vapor barrier.