Simulating the Daylight Performance of Complex Fenestration Systems Using Bidirectional Scattering Distribution Functions within Radiance

We describe two methods which rely on bidirectional scattering distribution functions (BSDFs) to model the daylighting performance of complex fenestration systems (CFS), enabling greater flexibility and accuracy in evaluating arbitrary assemblies of glazing, shading, and other optically-complex coplanar window systems. Two tools within Radiance enable a) efficient annual performance evaluations of CFS, and b) accurate renderings of CFS despite the loss of spatial resolution associated with low-resolution BSDF datasets for inhomogeneous systems. Validation, accuracy, and limitations of the methods are discussed

Approved Method: IES Spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE)

The metrics described in this document are intended to be applicable to common workplace environments. They are based on an analysis of open offices, classrooms, meeting rooms, multi-purpose rooms, and service areas in libraries and lobbies, and so are most applicable to areas with similar visual tasks. These metrics are neither counter to, nor do they supersede, IES task lighting criteria for these space types. These metrics do not directly address energy consumption, as electric lighting management is highly variable. The area of analysis for these metrics is ideally a coherent “space”, defined by opaque walls and access to daylight through at least one wall or ceiling surface. It is also possible to apply these metrics to the “regularly occupied” floor area of a building, or some part of a building, such as one floor plate. It is important to specify the “area of analysis” to which the percentages apply. These metrics were derived from a study of daylit spaces in the continental United States, and thus are most applicable to similar latitudes and cultures

Recommended Practice for Daylighting Buildings

This Recommended Practice conveniently gathers the basic data and techniques which help those concerned with the design of buildings and lighting systems understand and appreciate the opportunities and constraints inherent in daylighting. Daylighted buildings offer significant benefits that include visual and thermal comfort, occupant satisfaction, a connection to the outdoor environment, and reduced energy consumption, maintenance costs, and greenhouse gas emissions. Daylighting can result in significant electric lighting reduction in commercial buildings – 40% or more in side-lighted daylight zones and more than 50% is top-lighted daylight zones. The challenges of daylighting include glare, unwanted solar heat gain, the control of electric lighting, shading systems and coordination of the multiple disciplines affecting daylighting performance from initial planning to actual occupancy. In addition RP-5-13 also addresses daylight delivery methods and fenestration properties of various glazing systems, shading techniques, and control strategies. Measurements and daylight performance simulation tools are also described