When you are preparing to insulate an attic, the traditional choice of fiberglass batts might not be the best option. Blown insulation performs better than batts, and it is less expensive than spray polyurethane. Contributing editor Martin Holladay compares and contrasts two types of blown insulation, fiberglass and cellulose. Loose-fill fiberglass has a low R-value (2 to 2.7) per inch, so it is best applied in attics that have enough room to accommodate insulation 16 in. to 26 in. deep. Blown-in cellulose is made of ground-up newspaper mixed with a borate-based fire retardant. Because it is denser than fiberglass, it is more effective at reducing air leakage. Cellulose has an R-value of about 3.2 per in. Cellulose can be problematic if it becomes wet. Because it can absorb a lot of water, leaks can cause severe water damage before homeowners become aware of them via damaged drywall.
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