LBNL Report Number
Most commercial buildings utilize windows and other glazed envelope components for a variety of reasons. Glass is a key element in the architectural expression of the building and typically provides occupants with a visual connection with the outdoors and daylight to enhance the quality of the indoor environment. But the building skin must serve a crucial function in its role to help maintain proper interior working environments under extremes of external environmental conditions. Exterior temperature conditions vary slowly over a wide range and solar and daylight fluxes can vary very rapidly over a very wide range. The technical problem of controlling heat loss and gain is largely solved with highly insulating glazing technologies on the market today. The challenge of controlling solar gain and managing daylight, view and glare is at a much earlier stage. In most cases a static, fixed control solution will not suffice. Some degree of active, rapid response to changing outdoor conditions and to changing interior task requirements is needed. This can be provided with technology within the glass or glazing assembly itself, or the functionality can be added to the facade either on the interior or exterior of the glazing. In all cases sensors, actuators, and a control logic must be applied for proper functionality. Traditional manually operated mechanical shading systems such as blinds or shades can be motorized and then controlled by occupant action or by sensors and building controls. Emerging smart glass technology can dynamically change optical properties, and can be activated manually or by automated control systems. In all of these cases electric lighting should be controlled to meet occupant needs, while maximizing energy efficiency and minimizing electric demand. As with the fenestration controls, lighting control requires sensors (photocells or the human eye), actuation (switching or dimming) and a control logic that determines what action should be taken under each set of conditions. Some variation on the combination of all of these elements comprises the typical equipment and systems found in most commercial buildings today. The new challenge is to provide a fully functional and integrated facade and lighting system that operates appropriately for all environmental conditions and meets a range of occupant subjective desires and International Symposium on objective performance requirements. And finally these rigorous performance goals must be achieved with solutions that are cost effective and operate over long periods with minimal maintenance.