Parametric Modelling Using the Operative Temperature Map for Façade Design of Office Buildings

Abstract

Controlling incoming solar radiation to a building is one of the main targets of sustainable architecture designers because it decreases HVAC energy consumption and maximizes thermal comfort and usable daylight. The introduction of parametric design has allowed designers to expand their approaches to explore possibilities in façade forms and systems. However, most solar shading designs with complex geometries have been rejected by such building performance simulation software as Energyplus when assessing the calculation of thermal loads. To overcome this limitation, this research introduced a new framework using the Rhinoceros platform to simulate radiant discomfort across spaces with various types of parametric façades. The framework was established based on the ASHRAE55 appendix and improved the longwave MRT calculation by using the Radiance-based pre-processing method. The use of an operative temperature (OT) map was then highlighted as a measure of the combined effect of mean radiant and air temperatures considering the conditions of air velocity and relative humidity in office layouts. Designers were able to compare the hourly intensity of solar radiation passing through a façade between different design cases. Furthermore, the metric of Annual Thermal Discomfort Hours (ATDHs) and the Spatial Thermal Comfort Availability (sTCA) index were proposed for assessing the effect of solar radiation throughout a space. These dynamic indexes were adopted to evaluate different scenarios using the local climate thermal comfort statistics. Eventually, the simulation framework was validated by a field experiment which showed a high accuracy by R2=0.91. By the proposed study, designers can involve critical thermal sensation factors in the early design stage regardless of the complexity of the parametric facades.