WUFI sounds like a Star Wars character, but it’s actually an extremely useful software suite that calculates simultaneous heat and moisture transport in multi-layer building components.  It can account for literally hundreds of variables, from insulation size and type to window and door sizes and types to siding to typical weather conditions for the building site.  According to the WUFI website,,  “WUFI® is a family of software products that allows realistic calculation of the transient coupled one- and two dimensional heat and moisture transport in walls and other multi-layer building components exposed to natural weather. WUFI® is an acronym for Wärme Und Feuchte Instationär—which, translated, means heat and moisture transiency. The thermal and moisture conditions and transport in buildings and building components are coupled. It is well known that high moisture levels result in higher heat losses, and the temperature conditions in building components influence the moisture transport. Analysis of the coupling of heat and moisture is known as ‘hygrothermics.’”

The older method for assessing moisture performance in a building is the Glaser method.  To greatly simplify how it works, the Glaser method looks at static hygrothermic performance of each individual building component in an ideal situtuation, but it can’t look at how components effect each other’s performance, and it can’t simulate the effects of a specific climate in a specific location over time.  WUFI can.  WUFI rates a range of performance of the entire building in a specific location over a specific time period, so somebody building two identical office buildings, one in Denver and the other in Cleveland, will get different WUFI analysis results.  With the Glaser method, they would get the same results.

Given the number of variables WUFI can handle, it is, as you might expect, a very complex program and can take considerable time to master completely.  However, there are free “lite” versions available at that can help designers get started using WUFI.  May the force be with you.

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