Abstract
The extended degree day method is a simple and prevailing calculation procedure of term heat load for buildings. Nevertheless, it has some unresolved problems; the estimation of latent heat caused by rainfall at wall surfaces is one of them. The new extended degree day method is developed from the extended degree day method to estimate the effect of water evaporation at outdoor wall surfaces including glass windows. In this paper, the basic equations to transform the new extended degree day method are shown introducing heat balance equations and concepts of equivalent temperature and overall heat transfer coefficient at wetted wall surfaces. The evaporation ratio and the evaporative heat transfer coefficient are indispensable factors for the new extended degree day method to estimate the effect of latent heat exchange at outdoor wall surfaces of buildings. Identification of them is examined by thermal performance simulations using the standard weather data and precipitation data of Fukuoka. The validity of the new extended degree day method with these results is discussed through the comparison of term heat loads obtained by exact simulations, the original extended degree day method and our proposing new extended degree day method.
