'Window Appliance' Controls Light and Heat

We all know about low-E—that’s the window glazing that helps reduce a home’s heat loss via its windows, while often also cutting the transmission of solar heat into the home.

By Meghan Stromberg, Senior Editor | February 28, 2001
SageGlass windows, which feature an electrochromic coating, allow homeowners to control the amount of light and heat that enter the home by adjusting the tint.


We all know about low-E - that’s the window glazing that helps reduce a home’s heat loss via its windows, while often also cutting the transmission of solar heat into the home. Low-E windows have been touted for years as a key component in the energy efficiency game.

Now, there’s a young rookie in the glass game, training to be nothing short of the "future of windows," according to Mike Myser, vice president/sales and marketing of SAGE Electrochromics. What Myser is talking about is a type of glass that allows homeowners to control - and change - the amount of heat and light that enters through their home’s windows.

The company’s product, SageGlass, is a window glass with an electrochromic coating, which, as the name suggests, is a coating whose tint can be changed by an electric stimulus. In this case, a low DC voltage causes the coating, made up of multiple layers of ceramic films about 1/50th the thickness of a human hair, to darken. As the glass darkens, the penetration of visible light decreases, as does the transmission of heat.

Is this really energy efficient, you ask? How low of a voltage are we talking about here? Low enough that in an average house with an average number of windows, the operation of all SageGlass windows would require less electricity than a single 75-watt incandescent light bulb, according to SAGE literature.

"The ability to have a dynamic window that controls heat can have a very big impact on energy consumption," says Myser. And, although the technology is about 10 years old, concerns about durability have been one stumbling block to getting windows featuring the glass to market. SAGE has overcome that - and beat out its competitors - by using inorganic materials that won’t break down from exposure to UV and thermal stress.

SAGE has partnered with Honeywell to create the actual control technology by which homeowners will be able to regulate the tint of their windows. Calling the whole package a "window appliance" Honeywell says it will control the amount of heat and light entering the room, block glare, help keep indoor temperatures consistent and reduce fading to fabrics and furniture.

Chuck Hayes, Director of Honeywell’s Individual Comfort Business, says that each pane will have small, unobtrusive controls on-board that can be adjusted with a user-friendly device. Skylight prototypes, which will be tested in markets across the country starting in late summer, will feature a simple wall-mounted or remote-control, four-button interface. Real-life user feedback from the test markets will determine the product’s eventual design.

Perhaps more important than the design data of the market trials will be the results of the third-party energy efficiency tests. Hayes already anticipates that the final product may be able to cut air conditioning costs by a quarter or even a third. Neither Honeywell nor SAGE named possible partners, but both say plans are in the works to team up with window manufacturers. They also had no specifics on possible costs, but Hayes said that, like all products of this nature, the initial price tag will be relatively high. The companies are hoping, however, to be able to make the product affordable to most price points once it has achieved some market acceptance. Myser says the product should be introduced to the market in early 2003.