What is the cheapest roll of insulation?

The cheapest roll of insulation available at major retailers is usually a low R-value fiberglass roll meant for 2x4 walls or small projects. In 2026, the lowest-priced roll you will find at Home Depot and Lowe's is typically an R13 kraft-faced fiberglass roll, 15 inches wide by 32 feet long covering about 40 square feet, priced around $20 to $28 per roll. That equates to roughly $0.50 to $0.70 per square foot. An even cheaper upfront option is the R6.7 unfaced utility roll, often 15 inches by 39 feet, sold for about $18 to $24 and used for garages, sheds, or van conversions. While rolls are convenient, the cheapest insulation by coverage is actually blown-in cellulose or fiberglass bags when you use the free blower rental program offered by both big box stores. With that program, you can insulate an attic to R38 for about $0.35 to $0.60 per square foot. For true roll insulation, contractor-grade products like CertainTeed Builder's Blanket or store brands are about 10 percent cheaper than Owens Corning Pink Next Gen. Avoid reflective bubble foil rolls marketed as cheap insulation, as they only provide about R1 unless paired with an air gap and are not a substitute for fiberglass or cellulose for thermal performance.

The cheapest roll of insulation you can buy at retail is typically a low R-value fiberglass roll designed for small projects, like R6.7 or R13 kraft-faced rolls. As of 2026 at Home Depot and Lowe's, the cheapest commonly stocked roll is the Owens Corning or Johns Manville R13 kraft-faced fiberglass roll, 15 inches wide by 32 feet long, which covers about 40 square feet and costs around $20 to $28. That works out to about $0.50 to $0.70 per square foot. Even cheaper per roll is the R6.7 unfaced utility roll for 2x4 walls used for garage walls or van conversions, often sold as 15 inches by 39 feet for around $18 to $24. If you calculate by cost per R-value per square foot, the cheapest insulation overall is not rolls but blown-in cellulose or fiberglass bags, which cost about $0.30 to $0.50 per square foot at R38 when you use the free blower rental. For rolls specifically, store brand or contractor grade fiberglass like ProCat or CertainTeed Builder's Blanket is cheaper than Owens Corning Pink Next Gen by about 10 percent. The absolute cheapest material that provides any insulation is reflective bubble foil, sold for about $25 for a 4x25 foot roll, but its real R-value is only about R1 unless you create an air space, so it is not a true substitute. For real thermal performance, an R13 fiberglass roll is the cheapest legitimate roll insulation.