OVERVIEW

Fenestration is an architectural term that refers to the arrangement, proportion, and design of window, skylight, and door systems within a building. Fenestration components include glazing material, either glass or plastic; framing, mullions, muntins, dividers, and opaque door slabs; external shading devices; internal shading devices; and integral (between-glass) shading systems. In this chapter, fenestration and fenestration systems refer to the basic assemblies and components of exterior window, skylight, and door systems within the building envelope. Fenestration can serve as a physical and/or visual connection to the outdoors, as well as a means to admit solar radiation. The solar radiation provides natural lighting, referred to as daylighting, and heat gain to a space. Fenestration can be fixed or operable; operable units can allow natural ventilation to a space and egress in low-rise buildings.

Fenestration affects building energy use through four basic mechanisms: thermal heat transfer, solar heat gain, air leakage, and daylighting. The energy effects of fenestration can be minimized by (1) using daylight to offset lighting requirements, (2) using appropriate glazings and shading strategies to control solar heat gain to supplement heating through passive solar gain and minimize cooling requirements, (3) using appropriate glazing to minimize conductive heat loss, and (4) specifying low-air-leakage fenestration products. In addition, natural ventilation strategies can reduce energy use for cooling and fresh air requirements.

Today, designers, builders, energy codes, and energy-efficiency incentive programs [such as ENERGY STAR (http://www.energystar.gov) and the LEED Green Building Council (http://www.usgbc.org)] are asking more and...