The three-phase method for simulating complex fenestration with Radiance

The "three-phase method" is a means to perform annual simulation of complex and/or dynamic fenestration systems. Flux transfer is broken into the following three phases for independ ent simulation:

1. Sky to exterior of fenestration
2. Transmission through fenestration
3. Interior of fenestration into the simulated space

Rather than simulate a specific daylight condition, the three-phase method calculates normalized coefficients that relate flux input to output for each phase. A result for a specific daylight condition is computed by multiplying the coefficient matrices by the input values (sky luminance values). Matrix calculation can be performed very quickly enabling the user to simulate many sky conditions and fenestration transmission properties.

This document starts with a brief overview of the three-phase method. Following is a detailed discussion of each phase of flux transfer including an explanation of new tools that were develop ed for the three - phase method, explained in detail. Two examples follow the detailed discussion, the first a simple space with one south facing window, the second a space with south and east facing windows.