Hygrothermal component simulation is being used to evaluate constructions and construction details towards moisture-related damage potential. The simulation is also used for analysis and investigation of causes for occured damage. Mostly, 1D and 2D models are utilised, yet sometimes also 3D models, for example when looking at timber frame ends and critical construction details (corners/connected exterior walls). By default, the coupled heat and moisture transport is considered, whereby also air flow through cavities may be included in the calculation model. Additionally, numerous extensions of the core model exists, for example to evaluate/predict salt-related damage and/or pollutant emissions.

Partial differential equations describe the physical behavior of the building construction and its materials. These are being solved with numerical methods, most frequently with the Finite-Volume-Method (FVM) or Finite-Element-Method (FEM). In some rare cases still the Finite-Difference-Method is being used (which may lead to larger numerical approximation errors).

Because of the strong nonlinearities of the material functions the mathematical problem is strongly non-linear. Further, due to the very different and rapidly changing dynamics of the simulation, it is often difficult to solve a problem both accurately and efficiently. Currently, only a few software implementations exist, that solve these problems in a suitable manner. Given the complexity of the mathematical problem, implementing a solver is difficult and numerous error sources exist for parametrisation and implementation of the model.

The test series described below test individual subsets of a model and respective software implementations. They are all based on the unified and widely accepted mathematical formulation found in DIN EN 15026. However, currently there are no test and validation suites available that extensively verifies correct functionality of model components, that are today already frequently used in the planning practice. Despite the difficulty in correctly implementing 2D and 3D simulation models, there a no documentated or standardised test suites for 2D/3D geometries.

Validation suites and test series

  • DIN EN 15026 – The appendix of this Europian Standard defines a single test case that evaluates the calculation of a semi-infinite material slab exposed to a jump in boundary conditions
  • HAMSTAD Benchmarks – This series of 5 test cases evaluates to correct behaviour of the simulation for one-dimensional, multi-layered constructions

Literature

Articles/papers on the topic

  • Sontag L., Nicolai A., Vogelsang St., Validierung der Solverimplementierung des hygrothermischen Simulationsprogramms Delphinhttps://nbn-resolving.org/urn:nbn:de:bsz:14-qucosa-128968
    This article includes a detailed description of the validation of the simulation tool DELPHIN using the test cases of DIN 10211, 15026 and the HAMSTAD Benchmarks.