Performance
LBNL has been recognized worldwide for providing science and technology results that have had a meaningful impact in the field of daylighting. Two studies preceded the field tests conducted for this project: 1) a field test evaluating electrochromic window systems and 2) a collaboration with The New York Times in their development of a 52-story, 1.2 Msf corporate headquarters building in Manhattan that fostered the development of several new affordable, state-of-the-art energy efficient systems and created new knowledge about the building procurement process that was shared widely with other owners and design teams. Thousands of other building designers heard presentations on the results, or accessed reports and specifications from the project Web site. Technically, the daylighting control systems still have significant challenges ahead to improve system performance and reliability and address occupant requirements. This new DOE-CEC project has been initiated to further develop and promote such systems in partnership with owners and industry.
This R&D project commenced with a focus on interior shading devices, which have potentially broad market applicability in both new and retrofit markets in terms of ease of application and lower cost compared to core and shell improvements or renovations. LBNL has developed a unique full-scale windows testbed facility to test and evaluate the whole building performance impacts of integrated façade systems. Field studies conducted in this facility enable practical hands-on development and assessment of emerging façade prototype- and commercially-available solutions under real sun and sky conditions.
Interior views of the LBNL Windows Testbed Facility. A motorized daylight redirecting shade can improve the distribution of daylight illuminance across the entire room cavity by redirecting light to the ceiling. Sunlight can be reflected deeper into the room, potentially offsetting lighting energy use over a larger floor area. The brightness of the ceiling and the upper aperture itself can be a source of discomfort glare and needs to be studied further to determine the magnitude of the problem. The blind system operates over approximately a 180° range of motion. When the upper section is closed (left), horizontal view out is available in the lower section. When the upper section is opened to admit daylight (right), the lower section is closed to block direct sun and glare.
In the first phase of testing, daylight-enhancing interior shading systems and dynamic, motorized shades were monitored in a full-scale mockup of a commercial private office. Lighting energy use, cooling load, illuminance, and visual comfort data were monitored.
Results from this study showed that motorized interior shading systems with an integrated shade-lighting control algorithm met visual comfort requirements at all times of the day while delivering 62-69% lighting energy compared to a room with no lighting controls (from 1.0 W/ft2 down to 0.38 W/ft2). Daily cooling loads were minimally affected while peak cooling was decreased by 1-5% (10.6 W/ft2 decreased to 10.1 W/ft2 on sunny days) compared to a fully-lowered static shade.
Exterior motorized blinds are currently being tested at the LBNL Windows Testbed Facility.
Some of the innovative and conventional static shading systems delivered the same level of lighting energy savings but failed to create comfortable conditions for 20-30% of the day. Modifications to these systems (reduced surface reflectance or transmittance, for example) are likely to reduce lighting energy savings and so were not deemed to provide an optimal balance between glare and daylight requirements.
Exterior shading devices are being studied in a second phase of field testing (June to December 2008) since these systems can be more effective for low-energy cooling strategies.
Results from these field tests will be posted to this website as they become available. Links to prior published results can be found in the Resources section of this website.
