AGG
Volume 28, Issue 6 - November/December 2014

Glass Tech

A Switch in High Performance Building
Exploring the Ins and Outs of Dynamic Glazing
by Erin Roberts



Dynamic glazing products can provide energy savings through optimized use of natural daylight and reduced need for air conditioning, resulting in increased occupant comfort by controlling daylighting and glare. Dynamic glazing change its optical performance properties, such as visible light and near infrared transmission and solar heat gain coefficient.

Electrochromic Glazing

An electrical stimulus is used to change the light transmission and solar heat gain of electrochromic (EC) glazings. These glazings can be switched from a highly transparent state to a highly tinted state, stopping anywhere in between.

EC can be configured for manual control through a simple switch or automatically.

EC glazing has the ability to let as much light and heat into a building as desired based on environmental conditions such as glare, daylight levels or temperature and the needs of the building occupants, without loss of view to the outside.

Liquid Crystal Glazing

Liquid crystal technology has been used for more than 20 years as privacy glazing because it transitions from an opaque to transparent state. When power is off, the liquid crystals are in a random and unaligned state. The light transmission and the solar heat gain properties are not modulated so it provides little energy or glare control performance. As a result, this type of dynamic glazing is used most often for privacy in interior applications, such as bathrooms, and conference rooms.

Sunlight-Activated Glazing

Sunlight-activated glazing changes its light transmission and heat-gaining properties based on absorbed sunlight. These products continuously change their tint level based on the amount of the sun’s energy incident to the window. The absorbed sunlight warms the glass and causes the change in light transmission. Tinted glass and a variety of low-E coatings can be used in this laminated glass product.

Suspended Particle Device Glazing


Suspended Particle Devices are utilize two electrically conductive coated plastic layers with an emulsion containing suspended particles between the plastic layers, forming a film or sheet. This is then laminated between two lites of glass utilizing two adhesive interlayers—one on either side of the plastic-film. SPDs are electronically controlled to provide variable tinting. SPD can be in the form of a monolithic glass-plastic laminate or this laminate can be incorporated into insulating glass units with the addition of low-E glass.

Thermotropic Glazing


Thermotropic glazing—which can be reflective, absorbing and light scattering—is constructed with the active thermal component between lites. The visible light transmission changes when the ambient temperature exceeds an activating temperature set point. The product changes from highly transparent to a tinted reflective or light scattering state.

Energy Savings Benefits


In combination with low U-factor fenestration, and addressable, dimmable lighting controls an integrated solution can be provided to maximize energy efficiency and provide a clear path to achieving net zero.

Studies conducted by Lawrence Berkeley National Laboratory have shown electrochromic windows can save up to 60 percent of daily lighting energy and predicted commercial buildings relying on electrochromic systems could save up to 28 percent in energy costs versus buildings with static low-E windows.

Human Factors


Natural daylight through traditional glass products can benefit peoples’ health and well-being but can also cause thermal and visual discomfort. Dynamic glazing can significantly improve those factors while preserving the view and connection to the outside. Studies have shown productivity increasing by 0.5-5 percent annually with increased daylight and better control of office temperatures.

AGG

Erin Roberts is the director of marketing and communications for the Glass Association of North America in Topeka, Kan.

Architects' Guide to Glass & Metal
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