Insulation

Blown-in fiberglass - Spray Foam - Rigid Foam - Fiberglass Batts

Walls, Floors, Roofs, and Ceilings

Blow-in fiberglass consists of chopped glass fibers (and in same cases, an adhesive). The R-value of blown fiberglass increases with density and ranges from R-2.2 TO R-4.2 per in. High densities also help to lower air-infiltration rates.
Like cellulose, fiberglass can be blown into a closed cavity through drilled holes, installed behind air-permeable netting stapled to studs, or blown into open framing cavities, if the product includes adhesive. Among brands of blow-in fiberglass that include an adhesive, perhaps the best known is Jonhs manville's Spider. Spider fibers are fine and short, and special spray equipment adds a polyester-based liquid adhesive during installation. Dry spider fibers (without adhesive) also can be installed behind netting or dense-packed into wall cavities.
Typically installed on an attic floor, loose-fill fiberglass has a lower R-value per inch (R2.2 TO 2.7) than any other common insulation product, so it's best applied in attics that have enough room at the eaves to accommodate a very deep layer-as much as 16 in. to 26 in. The cost to install R-19 to R-21 blown-in fiberglass in a 2x6 wall is around 90 cent per sq. ft. To reach R-19 to R-30 in an attic, you'll pay from 65 cent to 96 per sq. ft.

Foam spray insulation

Made from polyurethane, this product reduces air leakage better than any other type of insulation. It fills the nooks and crannies of unusually shaped building cavities easily.
There are two main types of spray foam: open-cell spray foam, which has a density of about 1/2 lb. per cu. ft.; and closed-cell spray foam, which has a density of about 2 lb. per cu. ft. The higher the density of the foam, the greater the R-value per inch.
The two ingredients used to make spray foam conventionally called the "A" and "B" components are mixed on site using special equipment mounted in a trailer or truck. Heated hoses convey the chemicals to a mixing gun that sprays the chemicals on the surfaces to be insulated. An exothermic chemicals reaction begins as soon as the chemicals are mixed; the liquid mixture foams, expands, and eventually hardens.

R-VALUE: R-3.5 to R-3.6 per in.

COST: Varies widely, but filling a 2x4 cavity to R-13 with open-cell spray foam costs from about $ 2 to $2.75 per sq. ft.

APPLICATION: Walls, ceilings, and roofs.

The low density of open-cell foam make it relatively vapor permeable (a 3-in.-thick layer of open-cell foam has a permeance of 16), so it shouldn't be used to create an unvented conditioned attic in a cold climate (climate zone 5 and higher) unless the insulation can be protected by gypsum wallboard painted with vapor-retarding paint. if the foam will be left exposed, only closed-cell spray foam should be used in a cold climate.
Open-cell foams use water or carbon dioxide as the blowing agent. Some open-cell foams are made in part from bio-based raw materials-for example, soybean oils-in place of a portin of the petrochemicals.
Like closed-cell foam, open-cell foam creates an effetive air barrier.

Unlike closed-cell foam, however, open-cell foam adsorbs and holds water, has a lower R-value per inch, and is vapor permeable. The permeable of nature of open-cell foam can be a virtue or a drawback, depending on the application.

R-VALUE: R-6.5 per in.

COST: Varies widely, but filling a 2x4 cavity to R-13 with open-cell spray foam costs from about $ 2 to $2.75 per sq. ft.

APPLICATION: Walls, ceilings, and roofs.

Closed-cell spray foam provides a higher R-value per inch than less expensive insulation types like fiberglass, cellulose, or open-cell foam, all of which have R-valaue of R-3.2 to R-3.8 per in.

Closed-cell sprau foam is the most expensive residential insulation. When installed well, however, it performs better than any other insulation. It is an excellent air barrier, is imprevious to moisture, and is an effective vapor retarder. Becouse of its density and gluelike tenacity, it also adds strucutal strength to a wall, ceiling, or roof assembly. To seal air leaks in retrofit applications as well as new construction- for example, at rim joists or the attic side or partition top plates-closed-cell spary foam is an extremely useful material.

Many green builders avoid the use of closed-cell spray foam becouse the blowiing agent in most types of closed-cell spray polyuretahne foam are hydrofluorocarbons (HFCs) with a high global-warning potential.

Blown Insulation for Attics: Fiberglass vs. Cellulose

Synopsis: When you’re 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. The editor 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.