Citing recent research confirming that fiberglass insulation loses effectiveness in extremely cold temperatures, Minnesota has adopted a state building code revision which includes a requirement that "all insulation materials must achieve their stated performance at 75deg.F and no less than stated performance at winter design conditions."

Measuring R-value according to laboratory tests performed at an average of 75deg.F has long been standard industry practice, but the requirement that insulation must meet stated performance at "winter design" temperatures means manufacturers must provide additional information regarding the thermal performance of their products that are sold in Minnesota. For instance, CertainTeed is now including design coverage charts listing how much extra thickness is required at various winter temperatures to achieve desired R-values.

Because of the new standard, Owens-Corning has temporarily stopped selling its "Advanced Thermacube Plus" product in Minnesota. The company will continue to sell its higher density "Standard Blend" loose-fill insulation because documentation from tests performed a number of years ago supports the product claims. Meanwhile, Owens-Corning is building a new facility to test "Advanced Thermacube Plus."

The change in the Minnesota building code, which took effect in September, follows research conducted at the Oak Ridge National Laboratory (and corroborated at the University of Illinois) confirming that loose-fill fiberglass insulation loses as much as 50% of its effectiveness in extremely cold temperatures (10deg.F and -18deg.F). Heat loss through low-density, loose-fill fiberglass attic insulation increased significantly as the temperature differential grew between the heated space and the attic in the tests (See "Convection Loss in Loose-Fill Attic Insulation," HE, May/June '92, p. 27). Air densities changed with the temperature differences. As warmer air from the heated space below reached the top of the insulation, the air cooled, became more dense, and fell back into the insulation.

According to Thomas Newton, a spokesman for CertainTeed Corp. and the Mineral Insulation Manufacturers Assoc., any fiber and air insulation mixture can sustain R-value reduction at cold temperatures, but the problem is less pronounced with batt products.

To comply with the new standard, the industry will likely have to develop new winter performance testing procedures. An American Society for Testing and Materials (ASTM) subcommittee is now developing a standard test method to measure the in-service R-value of loose-fill insulation under "design" conditions. Currently R-values are measured with the ASTM C518 test procedure in which a sample is sandwiched between hot and cold metal plates maintained at 95deg.F and 55deg.F, respectively.

Meanwhile, a Minnesota law firm has filed a lawsuit against Owens-Corning, charging that the company deliberately misrepresented the quality of its loose-fill insulation since 1983, even after tests showed that in cold climates, the product did not achieve stated claims of effectiveness (see "How Effective is Insulation? HE, Oct/Nov '84, p. 27). The suit asks for compensation for money that homeowners have spent on excessive energy bills, and asks that the company re-insulate homes to meet its packaging claims . Prior to these tests, the conventional wisdom was that heat flowed through fiberglass insulation only by conduction and radiation. Owens-Corning concealed the test results, failed to disclose them to end-users, and therefore misrepresented its product performance, the suit alleges.

"As a consequence, end-users have continued to purchase and install Owens-Corning loose-fill insulation, and millions of dollars have been spent by such end-users to heat their homes, businesses, and other structures that would not have been spent had the Owens- Corning loose-fill fiberglass insulation performed as represented by Owens-Corning," states the suit.

The Minnesota Department of Public Service estimates that the convection problem may cost individual households about $20 per year, just from attic heat loss, and that about 200,000 Minnesota homes may be affected.

"The thing that is so irritating is the enormous cost to consumers that is literally going through the roof," said attorney Barry Reed of Zimmerman Reed, the firm which filed the suit. Owens-Corning denies Reed's charges. "As far as the class-action lawsuit, we don't think it has any basis and we plan to vigorously and rigorously contest it," said company spokesman Bradford Oelman. Owens-Corning has followed Federal Trade Commission rules, and long ago made product changes to increase the insulating value of loose-fill so that it would on average over a winter heating season deliver about the R-value stated on he label, Oelman said.

--Cyril Penn