The focus on efficient energy utilization in recent years has caused a revitalization in the study of natural daylighting and its use. As long as energy was considered cheap and available there was relatively little motivation to explore the tradeoffs between artificial lighting and natural daylighting. Now that the situation has reversed there are many daylighting projects under study.

The purpose of this work is to provide additional data to permit evaluation and optimization of energy utilization for office type applications with the use of daylighting. The major interest, therefore, is in the building thermal loads and the lighting energy required and not necessarily the other equally important qualitative factors associated with lighting. Instead of computing the energy input required by some type of RVAC system, the heating and cooling loads are presented. Separating the building loads from the rest of the system provides the possibility of studying the relative merits of some of the options available to architects and engineers at tile design stage without being overwhelmed by the type of HVAC system. It is recognized however that the relative input energy requirements for each parameter may be quite different than the building loads. For example, the manner by which a system responds to the everchanging building load can have a significant impact on tile energy use.

The scope in this work is therefore limited to the analysis of the sensitivity of the loads to four major parameters: window area, window/wall orientation, the type of glazing and the geographic location. Three particular locations, Detroit, Houston, and Denver, were selected to depict the influence of different climates. It is desirable to obtain, within practical limits, the lower and upper bounds of tile effects of the parameters so as to be able to infer the results for a wide range of values. For this reason the performance of the model was analyzed for ranges of window area from 0 to 100% of the exterior wall area with glazing materials ranging from the single clear to a product of the highest thermal performance such as an insulating and reflecting window. The results for operation without daylighting are used as a baseline of comparison for the daylighting mode.