What does roof insulation for shopping centers have to do with the Earth's ozone layer? A man-made chemical used in making foam roofing and sheathing insulation is due to be phased out, and mall owners, developers and architects need to know about the big change.

During the 1970s, scientists became concerned that certain chemicals could damage the earth's protective ozone layer. In the early 1980s, their concerns were validated by the discovery that the ozone layer over Antarctica was thinning to the extent that scientists and the popular press started talking about an ozone hole.

A compromised ozone layer - and the resulting increase in ultraviolet radiation hitting the Earth's surface - can have serious health consequences. Because of the risks posted by ozone depletion, leaders from many countries decided to craft a workable solution. Since 1987, more than 160 nations, including the United States, have signed the "Montreal Protocol on Substances that Deplete the Ozone Layer," which aims to reduce and eventually eliminate the production and use of man-made ozone-depleting substances.

The United States Congress amended America's Clean Air Act in 1992, adding provisions for protection of the ozone layer. Most importantly, the amended act required a gradual end to the production of chemicals that deplete the ozone layer. Because of their relatively high ozone depletion potential, several man-made compounds including chlorofluorocarbons, were targeted first for phase-out by the end of 1995, and many of them were replaced with compounds called hydrochlorofluorocarbons. HCFCs, while significantly less damaging to the ozone layer than CFCs, still deplete the ozone layer. Therefore, the EPA has put regulations in place to also phase out HCFCs.

HCFC-141b, which is used in making polyisocyanurate foam roofing and sheathing insulation, is the first HCFC to be phased out. The deadline for phase out of HCFC-141b is January 1, 2003. Currently, manufacturers are working on converting the plants that make foams with HCFCs to use approved replacements. Most companies have chosen to use hydrocarbons (pentanes) in the next generation of products. This technology is well known and has been used in Europe to make foams since CFCs were phased out.

How Changes Will Impact Building Owners The foam products that will be using hydrocarbons will have different properties compared to the current HCFC-based foams. The two main differences that will change the products will be an increase in strength and a reduction in thermal value. The increase in strength of the product will be an enhancement the users will appreciate. The reduction in thermal value will be from 8% to 10%, due to the lower insulating capability of a hydrocarbon gas. This difference could result in thicker materials being specified on jobs to meet design requirements. There does not appear to be any other difference that a user will notice with a hydrocarbon-blown foam compared to an HCFC-blown material. All other physical properties and fire properties will meet outside agency specifications and codes.