A Change for the Better: Polyiso Industry’s New Blowing Agent

There is a saying in the construction industry: If it works well, don’t change it. However in the case of the blowing agent change for polyisocyanurate insulation I expect people will stand up and applaud the initiative this industry has taken to create a product that is energy efficient and cost effective while taking a giant step towards improving the environment.

On Jan. 1, 2003, the polyiso industry began using new, zero-ozone-depleting blowing agents and zero-global-warming agents in the manufacturing of its foam insulation products. Blowing agents are one of the three basic components of polyiso insulation. The blowing agent is the ingredient that expands the foam and then remains contained in the closed cells, thereby enhancing the foam’s thermal performance. This new generation of polyiso foam insulation is manufactured with hydrocarbon blowing agents instead of HCFC-141b.

The use of hydrocarbons is the latest in a series of improvements the polyiso industry has made to help protect the stratospheric ozone layer. Seven years ago, the industry successfully converted from the blowing agent CFC-11 to HCFC-141b, resulting in a 90-percent reduction in ozone depletion potential over the previously used CFC-11. Polyisocyanurate Insulation Manufacturers Association (PIMA) members received the EPA’s Stratospheric Ozone Protection Award for this action. It was recognized at the time that HCFC-141b was to be phased out in the future and polyiso manufacturers began the search for a third generation blowing agent that would meet its requirements for performance in both the product and the environment. After extensive research, hydrocarbons were selected because they met all physical and thermal product performance requirements as well as environmental considerations.

This second industry transition has been smooth, and product performance has continued to meet industry standards. In fact, PIMA manufacturing members have installed over 1 billion board feet of the new polyiso throughout North America, over the past three years, and reported no difference in product performance. This is further supported by the extensive use of the new polyiso in Europe over the same time period, with similar results.

In addition to the change in blowing agent, the polyiso industry transitioned to a new methodology for determining the thermal insulation efficiency of permeably faced products — LTTR or long-term thermal resistance. LTTR represents the most advanced scientific method to describe the long-term thermal resistance of foam insulation products using blowing agents such as hydrocarbons. This method is based on accelerated aging by conditioning thin slices of foam insulation at a particular temperature for a specified number of days. The method is based on consensus standards in both the United States and Canada and provides a 15-year time-weighted average LTTR.

LTTR has many advantages. It provides a technically supported, more descriptive measure of the long-term thermal resistance of polyiso insulation. It applies to all foam insulation with blowing agents other than air and provides a better understanding of the thermal performance of foam. By using LTTR, the polyiso industry assists the architect and contractor in assuring the building owner that the sustainability of thermal performance of the roof system will be predictable over long periods of time.

Polyiso foam insulation continues to be one of the most energy-efficient and cost-effective insulation materials used in roofing applications today. Throughout the country, polyiso is the product of choice for the commercial roofing industry with an impressive 55 percent market share, according to an annual NRCA survey. Its widespread preference can be attributed to a number of factors. First, polyiso has the highest R-value per inch with long-term thermal performance validation. Second, polyiso is compatible with all types of roofing systems. And finally, polyiso meets both FM 4450 and UL 1256 for direct application over steel decks.