The building industry's embrace of "green" products has reached the home insulation market.

For decades, thick blankets of fiberglass insulation ruled attic and wall openings. The bats were joined by open-cell foams that were good insulators but had environmentally questionable side effects that depleted the ozone layer or released urea-formaldehyde that caused health problems when inhaled.

Use of these components was halted by the Environmental Protection Agency.

Homeowners already have seen rigid-foam insulators at work. For years, consumers applied small bottles of spray-on, rigid-foam insulation in and around cracks near doors and windows to seal off air flow. The insulation expands once applied and hardens when set.

Now, the insulation industry wants to expand that use between wall studs.

Ken Gayer, head of foam-blowing agents for Honeywell, says new, rigid, closed-cell foams are better insulators. Closed-cell foams have a higher insulation value compared with fiberglass and open-cell products.

There are differences between open- and closed-cell foams. Soft, open-cell foams are akin to a sponge and depend on the qualities of trapped air for performance. Rigid, closed-cell foam fills a space to seal off air flow and thus does not depend on trapped air as an insulator. The upshot is that cold spots and drafts are eliminated.

The energy savings can be substantial. Gayer says homeowners can expect to save 30 to 50 percent on home heating and cooling.

The closed-cell rigidness offers other properties attractive to both builders and homeowners. Tom Harris of BASF Corp., a user of Honeywell's foam-blowing agents, says the hardened foam adds to structural stability and is a better noise barrier than competing insulators. The drawback to rigid foams is cost. Gayer estimates spray foams cost $1.50 per square foot, compared with 75 cents for fiberglass. This adds roughly $3,000 to the cost of a home with 3,000 square feet of walls.