| Abstract | The purpose of this work was to review and document the implementation of heat, air and moisture transport equations in hygIRC. The lack of technical documentation has made it difficult to understand its implementation and to consider modifications to the program and as well, has hindered the development of hygrothermal models using more up-to-date software platforms. As such, the objectives of this exercise were to: • Review the fundamental equations implemented in hygIRC • Review how external and internal boundary conditions have been derived and implemented • Review how material properties have been implemented. In this work, as no particular reference was found that describes the algorithm used for hygIRC, a systematic review of the program was undertaken, in which instructions were reviewed step by step such that one could discern, having reviewed the program in its entirety, how the transport equations, material properties and boundary had been implemented. The primary findings of this report are summarized in the main body of the text whereas the implementation details are given in Annex I. In Annex II an example of a typical input file generated by the user interface is given. A description of the Delta-formulation for the Approximate Factorization method used for solving heat and moisture equations is provided in Annex III whereas in Annex IV are described the important variables appearing in the program. In the actual program, some of the critical parameters that form part of the material properties and that can have significant effects on the simulation results are not considered. For examples, the effects of temperature and hysteresis on the sorption curve, the effect of temperature on moisture diffusivity, the effect of saturation percentage on air permeability are not considered in the program. If the intent of the simulation is to perform comparisons (i.e. two locations, two sets of climate data, etc.), this then is less critical. However, for the purposes of design and for which a clear understanding of the effects of climate loads on building envelope are needed to permit assessing the durability of the envelope components and assemblies, efforts should be made to properly characterize the material properties and to implement them in the program. |
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