NBN EN 15026:2007

This standard specifies the equations to be used in a simulation method for calculating the non steady transfer of heat and moisture through building structures.
It also provides a benchmark example intended to be used for validating a simulation method claiming conformity with this standard, together with the allowed tolerances.
The equations in this standard take account of the following storage and one-dimensional transport phenomena:
- heat storage in dry building materials and absorbed water
- heat transport by moisture-dependent thermal conduction
- latent heat transfer by vapour diffusion
- moisture storage by vapour sorption and capillary forces
- moisture transport by vapour diffusion
- moisture transport by liquid transport (surface diffusion and capillary flow).
The equations described in this standard account for the following climatic variables:
- internal and external temperature
- internal and external humidity
- solar and longwave radiation
- precipitation (normal and driving rain)
- wind speed and direction.
The hygrothermal equations described in this standard shall not be applied in cases where:
- convection takes place through holes and cracks
- two-dimensional effects play an important part (e.g. rising damp, conditions around thermal bridges, effect of gravitational forces)
• hydraulic, osmotic, electrophoretic forces are present
daily mean temperatures in the component exceed 50 °C.