Quantification of uncertainty in thermal building simulation - Part 2: Stochastic building model.

In order to quantify uncertainty in thermal building simulation stochastic modelling is applied on a building model. Part l deals with the stochastic thermal building model and a test case. This paper deals with the determination of the stochastic input loads. The importance of obtaining a proper statistical description of the input quantities to a stochastic model is addressed and exemplified by stochastic models for the external air temperature and the solar heat gain. Each of the external climate parameters is modelled as a stochastic process with time varying mean value function superimposed by a time varying standard deviation function. The statistics of the external air temperature is obtained by means of Fast Fourier Transform (FFT). A model of the solar heat gain is presented, considering the obvious fact that solar radiation is present only during daytime. The Danish Design Reference Year (DRY) is used as experimental data.