More than 250 sales representatives, customers and other guests attended a special AHSRAE breakfast and press conference last month to celebrate the production of a half-a-billion feet of Wirsbo PEX tubing in North America. Among those speaking was This Old House plumbing and heating expert Richard Trethwey, one of the nation's leading advocates of radiant floor heating. Wirsbo was incorporated in 1984 and was the first in North America to market PEX tubing for radiant floor heating systems. Wirsbo also led the development of ASTM Standards F876 and F877 for the PEX industry.