LBNL Report Number
The U.S. General Services Administration (GSA) Public Buildings Service (PBS) has jurisdiction, custody or control over 105 land ports of entry throughout the United States, 35 of which are located along the southern border. At these facilities, one of the critical functions of windows is to provide border control personnel with direct visual contact with the surrounding environment. This also can be done through surveillance cameras, but the high value that U.S. Customs and Border Protection (CPB) officers place on direct visual contact can be encapsulated in the following statement by a senior officer regarding this project: “nothing replaces line of sight.” In sunny conditions, however, outdoor visibility can be severely compromised by glare, especially when the orb of the sun is in the field of view. This often leads to the deployment of operable shading devices, such as Venetian blinds. While these devices address the glare, they obstruct the view of the surroundings, negating the visual security benefits of the windows.
Electrochromic (EC) windows have the ability to adjust their tint dynamically in response to environmental conditions. This provides the potential to control glare by going to a dark tint at times when extreme glare is likely. In previous studies, these windows have shown that this ability to control glare has the potential to increase the amount of time during which view is unobstructed. This technology is available in the U.S. as a commercial product from two vendors with high-capacity manufacturing facilities, and could be deployed on a nationwide scale if successful in a pilot test.
In this project, EC windows were installed at a land port of entry near Donna, Texas. The technical objectives of the study were to determine whether the installation of the EC windows resulted in the following:
- Reduction in visual discomfort caused by glare from daylight and direct solar orb visibility
- Reduction or elimination of need for operable shading deployment
- Improved tenant satisfaction with visibility to the outside
- No significant negative impact on visibility of the exterior due to the decrease in window transmittance.