Batts, Blown-in or Sprayed Insulation: Which Is Best?

What’s the best insulation for your house? Put simply, the purpose of insulation is to inhibit the movement of heat. In summer, insulation prevents unwanted heat gain into the house while in winter it reduces heat loss. When existing insulation is insufficient, heating and cooling costs tend to go up and indoor comfort declines. To help evaluate the best insulation for your needs, here’s a summary of what’s available:

Fiberglass Batts

The most common insulation in residential applications, batts are roll-out blankets of fluffy, cotton candy-like insulation, pre-cut to fit between joists in the attic. Fiberglass batts are the least expensive choice to effectively minimize heat gain and loss.

Insulation’s effectiveness is rated by its “R value” of installed thickness. Fiberglass batts offer an R-value of 3.2 per inch. In our climate zone, the Department of Energy recommends insulating in the range of R38 to R60 in the attic, an amount equivalent to 12 inches up to 18 inches of fiberglass.

Blown-in Cellulose

Cellulose insulation is composed of particles of pulverized paper or cloth, blown in under air pressure through large hoses. Cellulose can be installed between attic joists or injected into wall voids through small access holes.

With an R-value per inch of 3.8, DOE recommendations call for insulating the attic to a depth of 10 inches up to 16 inches of cellulose. Exterior wall cavities should contain 3.5 inches to 4 inches.

Spray-On

Spray polyurethane foam (SPF) insulation can be applied attic surfaces and injected into wall voids. A two-part formula prayed under pressure, SPF offers superior insulating properties around R-6. In addition, SPF also seals structural air leaks and forms a moisture barrier.

Application of SPF requires trained professionals with specialized equipment. It’s therefore generally the most costly home insulation alternative—as much as two to three times higher than fiberglass or cellulose.