Natural Daylighting - An Energy Analysis

Abstract

To promote energy conscious design, a study was undertaken to analyze the implications of using daylighting in the design of a structure. An existing office building was selected for this study. Its specific construction features, materials, usage patterns and equipment were determined. From this data, its energy consumption was estimated using LOADCAL: a computer program based upon the ASHRAE methodology. Then, daylighting levels within the building were estimated. Modifications to the structure were evaluated to determine if daylighting could be used more efficiently in the building. Two new glazing types were considered in this study. Evaluations were first made using a glass with a similar shading-coefficient but a higher visible-light-transmission than the existing glazing. This approach yielded excessively high illumination levels and was, therefore, unacceptable. In the second approach, a glazing with a similar visible-light-transmission factor but a lower shading coefficient was used. This yielded striking results. By modifying the building with the new glazing and incorporating the available daylighting to reduce the existing artificial lighting level, a significant reduction in the estimated energy consumption was realized. The improved performance characteristics of the new glass, coupled with the reduced artificial lighting levels yielded a total energy reduction of approximately twenty-two percent.