Paper Conference

Proceedings of BauSim Conference 2008: 2nd Conference of IBPSA-Germany and Austria


Einfluss des Klimas (Innen und Außen) auf das hygrothermische Verhalten von Außenbauteilen

Andreas Holm

Abstract: The hygrothermal behaviour of building components is very important, due to the effects of weathering and ground moisture as well as increased air-tight construction and higher indoor relative humidity. The indoor air temperature and relative humidity must be known parameters besides outdoor climate boundary conditions to carry out hygrothermal computation of building components. The indoor climate is determined by the behaviour of the users in contrast to the outdoor climate. The thermal capacity and water vapour sorption capacity of the internal components and furniture, however, provide a slightly dampened progress of air temperature and relative humidity. Hourly measurement values are therefore only necessary, if special problems occur. More exact values for the real conditions of indoor environments, especially for relative humidity, have not always been measured. Indoor boundary conditions according to DIN 4108-3 for the dew period and the evaporation period can only be „generally“ applied for simple steady-state methods, e.g. the method of Glaser, and comprise security aspects. But it is impossible to calculate the real behaviour of building components in this way. This shortcoming became obvious in the past few years and resulted in extensive data acquisition of occupied and unoccupied rooms, aimed at determining the representative annual progressions of indoor air conditions. More exact predictions on the indoor environment, occurring in interiors, especially relative humidity, can be achieved by means of hygrothermal indoor climate simulations under the condition that all nonstationary influencing factors are taken into conside 47 IBPSA Zweite deutsch-österreichische IBPSA-Konferenz Universität Kassel BauSIM 2008 ration. Numerous models were developed in the past few years to compute the thermal behaviour of buildings, which have become a routine application in building design in the meantime. Besides the energetic assessment of the indoor environment, the combination with humidity processes in the enclosure surfaces is required. But so far, previous computation models offer only relatively simple approaches on humidity behaviour. The combined effects of nonstationary sorption, diffusion and capillary duct processes in the enclosure surfaces are not at all or only insufficiently considered. Yet the latter play an important role. The objective is to investigate the impact of standard boundary conditions or hourly measured indoor climate simulation values on the behaviour of the building components of a wall or roof construction. For this purpose, hourly measured weather data of a typical year for the Holzkirchen location served as climate outdoor boundary conditions. Indoor boundary conditions for hygrothermal building component simulations are differently handled at present. The standard EN-ISO 13788 has been especially developed for steady computations according to Glaser, and the standard EN-ISO 15026 for non-stationary building component simulations. In addition, a data sheet for hygrothermal building component simulations was established by the International Association for Science and Technology of Building Maintenance and Monument Preservation (WTA), which is valid especially for Central European countries.
Pages: 47 - 48