Curtain wall is becoming an increasingly sophisticated building envelope system. A current and continuing trend, according to Kirt Osgood, vice president and principal of Dallas-based Curtain Wall Design and Consulting, is control of solar gain. This is reflected in the widespread use of low-emissivity glazing, which reduces heat loss in the winter and heat gain in the summer.
Exterior sunscreens and other sun-control devices are helping to promote interior daylighting, reducing the need for artificial lighting. Some exterior walls even have integral photovoltaic systems, which generate solar-produced electricity.
According to Osgood, these technologies are even more advanced in Europe because of the higher cost of electricity.
Curtain wall is also moving toward blast resistance, as laminated glass is increasingly being specified for courthouses and high-security buildings that require heightened security. More traditional blast-resistant façades include nontransparent materials such as precast concrete and stone.
A new development is "self-cleaning" glass, which incorporates a coating that lets sunlight and the dispersion of water droplets assist the cleaning process (see page 47).
Curtain wall has historically been constructed on the building site, but current practices indicate a continued movement toward unitized curtain wall, Osgood says. Aluminum, stone or glass units are pre-engineered and fabricated in a factory and shipped to the site.
"Workmanship is improved in a more controlled environment, creating a better quality product and a better performing system for the building," says Osgood.