Lighting is the single largest consumer of electricity in an office building. Therefore, the simple idea behind daylight harvesting is to reduce the need for artificial light through the use of natural daylight. Here is how we dramatically reduce our building's consumption of electricity for lighting:
Our building's design incorporates many internal and external glazing systems. More than 90 percent of our building's regularly occupied spaces provide a direct line of sight to the outdoor environment via vision glazing.
With ample external glass on three sides, including 40-foot-high glass curtain walls on the building’s east and west sides and a 10-foot-high glass south wall, the building lets in natural light while providing picture-perfect views of the countryside. In addition, all offices and meeting spaces have external and/or internal glazed openings, allowing both direct and indirect access to natural daylight.
To take full advantage of natural light, we located many lighting sensors around the building, which constantly monitor light levels. These sensors inform our Building Automation System (BAS), which automatically dims and/or turns lights on and off based on the lighting levels reported by the sensors. This system ensures that only the exact amount of artificial lighting is enabled to fulfill the real-time needs of the building occupants.
Natural lighting can also have some unwanted effects, such as glare and harsh sunlight. To control for this, we installed an automated window shading system that deploys shades on the external windows when needed. Internal and external sensors, as well as a database of lighting condition measurements of our building’s location, inform our BAS, which controls the window shading system and blocks any glare.
Through our daylight harvesting system, automated lighting occupancy sensors and the use of Light-Emitting Diode (LED) lighting and Compact-Florescent Lighting (CFL), we have reduced our building’s lighting electricity use by more than 50 percent.