Because heat energy is always trying to either escape your house or invade your house, adequate insulation is what’s required to keep heat where it is. In winter, holding heat energy inside is the goal; during summer, keeping heat outside is vital. Insulation retards the flow of heat energy in either direction, making the proper amount and type critical to household comfort and energy efficiency.
Insulation efficiency is expressed by its R-value per inch of depth or thickness. Current Department of Energy recommendations for our climate zone call for insulating to a range of R30 to R60 in the attic and R13 to R15 inside exterior wall cavities. Here are three common insulation types:
Fiberglass Batts
These are familiar roll-out blankets of fluffy, cotton candy-like material. Batts are the most common residential insulation, most often installed in the attic to reduce heat transfer through the ceiling. For our climate zone, the DOE recommended R-value range translates to 10 to 20 inches of fiberglass batts in the attic or 4 to 5 inches inside wall cavities.
Cellulose Loose Fill
Composed of pulverized paper particles blown into the attic under air pressure or injected into walls through small access holes, cellulose provides excellent coverage as particles fill even small, irregularly shaped areas. For that reason, cellulose delivers a higher R-value per inch than fiberglass. Here in San Diego, the recommended attic depth ranges from 8 inches to 16 inches. Inside walls, cellulose particles are usually blown in to fill the entire void.
Spray Polyurethane Foam
A two-part mixture applied wet to surfaces in the attic, crawl space and basement, spray polyurethane foam (SPF) can also be used to coat the inside of exterior wall voids. The high-efficiency closed-cell variety provides outstanding R6.5 insulating value. As it dries, SPF expands to provide excellent coverage, filling gaps and forming an effective air barrier. The closed-cell type is more expensive than most other insulation options. SPF also requires experienced technicians with specialized equipment to apply it correctly for optimum performance.