Calculating heat and moisture

A German-U.S. computer program can help roof system designers

New computer programs are introduced so frequently, it often can be difficult to determine which ones are worth your time and money. In the roofing industry, there is no shortage of programs promising to make things easier for contractors and designers. One program that has recently been introduced to the design community is known as WUFI.

WUFI stands for the German words Wärme-und Feuchtetransport instationär. The English translation is "transient heat and moisture transport." WUFI is a sophisticated computer program that calculates heat and moisture transport through roof and wall assemblies. It was developed by the Fraunhofer Institute for Building Physics (IBP), Stuttgart, Germany, and introduced in Europe in 1994. A few years later, Oak Ridge National Laboratory (ORNL), Oak Ridge, Tenn., partnered with IBP to modify and improve WUFI for use in North America. The North American version was released in 2001.

I heard about WUFI a few years ago but did not look into it until I was retained by a client to investigate a problematic roof system. A consultant representing another party included a WUFI analysis in his report on the problem. At the time, I didn't have enough knowledge of WUFI to evaluate the analysis, so I retained the services of another roof consultant familiar with WUFI to assist me. I came to the conclusion that it was important for me to gain a better understanding of WUFI and decided to attend a two-day training workshop conducted by ORNL.

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