Radiometric Boundary Condition Models for Building Performance Simulation: An Empirical Assessment

Abstract

Designand operation of buildings in view of optimal thermal and visual performance can benefit from deployment of appropriate simulation tools. Specifically, the design and configuration of building-integrated renewable energy systems (solar-thermal collectors and photovoltaic panels) can be effectively supported via reliable computation of incident solar radiation. Toward this end, advanced building energy and lighting simulation programs typically use high-resolution sky models. In this contest, the present contribution addresses the reliability of these models based on long-term high-resolution data collected at the observatory of the Department of Building Physics and Building Ecology at the Vienna University of Technology, Austria. This observatory is equipped with radiometric and photometric sensors to measure global and diffuses horizontal irradiance and illuminance, global vertical irradiance and illuminance of the four cardinal orientations, as well as sky radiance and luminance values for discrete sky patches. To evaluate the performance of two widely used sky models, we compared simulated and measured vertical irradiance values as well as patch radiance values. The statistical appraisal of the comparison points to limits in the predictive accuracy of both models.