BEEM (Building Energy Estimation Module) is a simple hand-calculation procedure to calculate window-related building energy impacts, including daylighting electric lighting, cooling, and heating energy. It was developed under a previous ASHRAE research project. Reported here are subsequent derivations and successful validation using DOE 2.1b energy prediction computer program.

The fill-in-the-blanks procedure, also adapted to micro-computers, was created for use in the schematic building design stage by architects and engineers to make early quantitative design decisions on glazing types and sizes, and on daylighting controls. Included are the calculation of interior daylighting levels due to a given window as well as the yearly lighting, cooling, and heating energy costs due to the window relative to a solid wall. Workplace daylighting level and lighting-savings-fraction are calculated for both June 21 and December 21. Yearly energy cost is calculated so that various fenestration alternatives can be compared for optimizing the total economic impact.

The procedure requires about 30 minutes for reading instructions and completing an energy calculation for one window situation. Subsequent calculations take 10 to 15 minutes; changing one parameter and re-calculating requires about 5 minutes. The procedure is easily coded on a micro-computer and such a code has been prepared using CP/M. Both a long form (with helpful narrative) and a short form (for subsequent faster calculations) are available.