Paper Conference

Proceedings of eSim 2004: 3th Conference of IBPSA-Canada



Akihito Ozaki, Toshiyuki Watanabe, Shuho Takase

Abstract: A Heat, Air and Moisture (HAM) simulation software program called THERB for has been developed for the purpose of estimating the hygrothermal environment within buildings. Authors have already developed THERB as a simulation software tool to estimate the thermal environment within residential buildings, however the new THERB program has been expanded to include complete HAM features including principles of moisture transfer within walls. Generally simulation software to predict temperature, humidity, heating and cooling load of building spaces does not take into account moisture transfer in wall assemblies. Humidity calculation in most software is simply affected by ventilation and focuses on just the building spaces. THERB for HAM was developed to simulate humidity conditions in both building spaces and wall assemblies in detail. THERB for HAM excels in the theories for describing actual building physics. Most of thermal theories on radiation and convection and ventilation utilize existing models already developed for THERB, however the water potential, which is defined as thermodynamic energy, is a newly adopted feature of THERB, which incorporates moisture transfer including moisture sorption and desorption of walls. Authors have also proposed such a moisture transfer model called P-model and developed simulation software to analyze moisture behaviour in wall assemblies. Thus THERB for HAM represents the combined simulation software capabilities of the original THERB software and the new features of the P-model, which can now predict the hygrothermal environment of the whole building (all spaces and wall assemblies of the building) taking into consideration the complex relationship between heat and moisture transfer and air flow. In this paper, the basic theories used in THERB for HAM are described. Accuracy of THERB for HAM is verified through the comparison of calculation and monitoring results of a residential building. Furthermore the difference of calculation results is clarified based whether or not moisture sorption and desorption of walls are taken into account.
Pages: 45 - 54