European standard EN 15026 provides minimum criteria for simulation software used to predict one-dimensional transient heat and moisture transfer in multi-layer building components exposed to transient climate conditions on both sides.
The standard lists model equations and pertinent material properties which shall be used for computing heat and moisture transport phenomena. These model equations allow for the following storage and transport phenomena:
- heat storage by the dry materials and the absorbed water,
- heat transport by moisture-dependent thermal conduction,
- latent heat transfer by vapor diffusion,
- moisture storage by vapor sorption and capillary forces,
- moisture transport by vapor diffusion,
- moisture transport by liquid transport (surface diffusion and capillary flow),
and the following boundary conditions:
- indoor and outdoor temperature,
- indoor and outdoor humidity,
- solar and long-wave radiation,
- precipitation (normal and driving rain),
- wind speed and direction.
Furthermore, the standard adopts several simplifying assumptions; for example, swelling and shrinking processes, chemical reactions and ageing processes are ignored, the moisture storage function is treated as independent of temperature, etc.
WUFI® complies with all requirements of standard EN 15026.
Standard EN 15026 defines a benchmark example for validating hygrothermal simulation software. It is designed to ensure that the software meets some basic requirements and produces results which are correct within a specified tolerance. The example considers the heat and moisture absorption of a semi-infinite slab of material which initially is in equilibrium with the boundary conditions ϑ = 20°C, φ = 50% and then is subjected to the new conditions ϑ = 30°C, φ = 95%.
The sudden increase of the temperature and moisture content at the surface causes heat and moisture to flow into the material. The temperature and moisture profiles resulting after 7, 30 and 365 days are to be calculated. The results of the software under test must not deviate from the reference solution by more than 2.5 %.
WUFI’s results for the benchmark example are virtually identical with the reference solution (see diagrams), it therefore complies with the requirements established by EN 15026.
You can download a WUFI Pro project file (WUFI® Pro 4 (25kB), WUFI® Pro 5 (11kB) oder WUFI® Pro 6 (11kB)) for the benchmark calculation. An accompanying PDF file (513 KB) states WUFI’s compliance with EN 15026 and documents how the benchmark specifications have been translated for use with WUFI® .
Last Update: October 20, 2020 at 10:18