Simplified daylighting energy savings for non-daylighting building energy simulation programs: Fid-Bau Portal

Simplified daylighting energy savings for non-daylighting building energy simulation programs

Ander, Gregg D. / Maeda, Bruce T.

AbstractThe California Legislature mandated the California Energy Commission (CEC) to establish and periodically update energy efficiency standards for new buildings. To this end, a sensitivity analysis was conducted by the Standards Development Office of the California Energy Commission for nonresidential buildings. The purpose of this parametric analysis was to determine which variations in building parameters actually have significant energy impacts.A “generic” building model was developed and implemented in conducting this sensitivity analysis. The generic model was used as an analytical tool in modeling the energy impact of building parameter variations, as well as architectural and mechanical energy-saving measures on the energy use of each module. It is recognized that the level of significant energy impact is equivalent to, or bounded by the accuracy of the energy analysis tools in predicting energy usage in actual buildings. For the computer program used, DOE 2.1A this accuracy is within ±5%.Since DOE 2.1A and most of the other building energy simulation programs do not have daylighting algorithms, another calculation tool was used to determine daylight availability and lighting power reduction on an hour-by-hour basis for each orientation. This is accomplished with a daylight reduction factor (DRF).Quicklite, a simplified daylighting program, calculated footcandle (lux) levels based on outdoor ambient light levels, physical room dimensions and properties. To assess the impact of the Quicklite calculated footcandle (lux) levels on artificial lighting use, a control scheme was assumed, and a DRF was calculated based on annual sky conditions by climate zone.Once the DRF values are known for each orientation, the electric lighting schedule can be modified. A new profile number, representing the proportion of installed lighting switched on at that hour, replaced the daily lighting schedules when daylighting was utilized (09:00 – 17:00). To test this methodology, a sensitivity analysis was conducted between DOE 2.1A with Quicklite modifications and DOE 2.1B which has a daylighting preprocessor. The results displayed a 3.6% variation in total energy use.We conclude that daylighting calculations for design days using simplified programs can be used to approximate daylighting energy savings in building energy simulation programs that allow zoned lighting schedules but do not calculate daylight contributions.