Moisture safety is a rising concept in the construction industry and building designers spent
more and more time on the moisture safety designs. Moisture is complicated to calculate and
the use of a calculation program could make the process easier. Wufi is a German moisture
calculation program that recently has been presented in a Swedish version. WSP has invested
in the program to better assess the moisture safety in structures. WSP was interested in a study
of Wufi to facilitate the introduction of the program in the company. The objective of this
report is to clarify how the basic parameters are to be considered in the program and how
reliable the program is.
In order to make an evaluation possible the process started with self-study of the program, and
ended with a short education in the program. After this a number of parametric tests were
conducted in the program to answer how these should be dealt with. For the assessment of the
reliability of the program a major study on plaster walls with different plaster system was
made. The results were compared with the problems that have occurred on these structures.
The parameter tests shows that material properties have a major impact on the outcome and it
is therefore important to use materials in the right way and with the right values. The test of
time steps indicates small difference in outcome. Calculations in the program can therefore be
carried out with an hour time step and thus minimizing the calculation time.
Used correctly, the Wufi program and its parameters provides reliable results. The result from
the plaster walls in Wufi follows the implications and discussions that have aroused about the
plaster on wood frame. However, the application is entirely dependent on what you choose for
input and material properties. If these are not carefully controlled, there is a risk that the
results are wrong and the reliability of the program is then gone.
For the program to reach a useful position in an organization such as WSP, an update of the
material database ought to be done. This increases the usability significantly and building
designers who do not normally work with building physics could then be able to determine
the moisture safety in a construction. In order to maintain control over moisture safety,
however, there should be clear policies for how the program should be used.