A Simplified Method For Calculating The Effective Solar Optical Properties Of a Drapery

Abstract

The use of draperies to control solar gain through windows is common in residential and commercial buildings and their potential for reduction of building peak load and annual energy consumption is recognized to be large. Thus, there is a strong need for models that allow a drapery to be included in glazing system analysis. As an approximation, the drapery is modelled as a series of uniformly arranged rectangular pleats with fabric transmitting and reflecting diffusely any incident radiation. The “effective” solar optical properties of the drapery are then determined by considering an enclosure which is representative of the entire series of pleats. The optical properties of the drapery are functions of the pleat geometry and the optical properties of the fabric. Optical properties are also influenced by the directional nature of the incident radiation. In the case of incident beam radiation, the results are presented as a function of the solar profile angle for a folding ratio corresponding to 100% fullness. The results for incident diffuse radiation on the other hand are presented in terms of fabric properties and the folding ratio of the drapery.