Lawrence Berkeley National Laboratory has been collaborating with the window industry to develop and evaluate daylighting technologies that can reduce lighting energy use by as much as 50 percent up to 40 feet from windows, according to Berkeley Lab.
An example is a collaboration Berkeley Lab has developed with the 3M Corporation. 3M developed a microstructured prismatic film consisting of linear multi-sided prisms 50 to 250 micrometers high. Results from the partners’ simulation analysis indicate that a small clerestory window with the 3M dual-film system and a lower window with conventional shades can daylight a 40-feet deep perimeter zone facing south, east, or west in virtually all US climates and save up to 40 percent of annual lighting energy compared to the same zone with no daylighting controls.
Researchers in Berkeley Lab’s Environmental Energy Technologies Division (EETD) corroborated these findings with measured data in Berkeley Lab’s Advanced Windows Testbed facility (pictured).
EETD researchers are helping companies such as 3M by using simulation tools (Radiance, Window, EnergyPlus, COMFEN) and new measurement facilities to accurately assess where and how much solar radiation and daylight flux can be effectively controlled by new optical materials and systems. Using these tools, calculations of energy use and visual discomfort can be done more accurately and in a fraction of the time needed in the past. As a result, industry partners can now determine how well new optical designs will work long before they invest a lot of time and resources into prototype fabrication and testing in the field.