Best Of Show: Sage Electrochromic Glass Is A Thermostat For The Sun


Image credit Lloyd Alter
Sage Electrochromic glass has been on the TreeHugger radar for a while; we first covered it in 2006 and Mike expanded on it last year.

It is a fascinating product, glazing that darkens at the flip of a switch, eliminating the need for blinds and maximizing natural light. It was only after I spent an hour in the booth talking to Vice President Lou Podbelski that my brain exploded when I started considering the real architectural possibilities of the stuff.
Images Credit Sage

The glass is made by depositing thin layers of materials through ion sputtering, the same technique used for depositing the coating on conventional solar control glazing. When a charge is applied across the sandwich, positively charged lithium ions migrate from the Counter-electrode (CE) layer to the electrochromic later (EC), where it darkens the material by some process that is not yet clear to me. But the key is that this is fairly straightforward, low voltage, long lasting (tested so far for 50,000 cycles) and not out-of-this world expensive, especially when one includes the savings in air conditioning loads and automated blinds in conventional commercial installations.

Sage is selling glass, so it should be no surprise that their marketing talks about how this product lets you use a lot more of it. The architect says:

SageGlass helped me exceed my customer's expectations by allowing me to design a beautiful showcase building with abundant use of glass, without compromising their sustainability goals.

And there is no question, it works really well for that. If it gets too bright and too hot, you can just dial it back. According to Sage " It reduces cooling loads in buildings by 20 percent, HVAC requirements by 25 percent, and lighting energy costs by up to 60 percent."


The GO Home Passive House
A Thermostat For The Sun

The Sage website is all about maximizing natural light while minimizing cooling loads. But I had spent the morning in a presentation about Passivhaus or Passive House design, where solar heat gain is a major part of the energy equation and calculation; the sun is pretty much the furnace that heats the house. It is an unruly furnace; it is hard to turn off in the summertime and hard to control any time.

On the south side of houses, tools for controlling sun range from louvres and brise soleil to grape vines. On the east and west sides, where the sun does not vary in altitude with the seasons as much, it is almost impossible to control.

I left the Sage Booth in a bit of a daze, thinking about its possibilities as a thermostat for the sun, the solar furnace that drives a Passivhaus. I think it might make the Passivhaus far more comfortable and easy to manage. Given that Passivhaus windows are already expensive, this might not even add that much to the cost of them.

For both commercial and residential buildings, this is a game-changer. It's not just about using more glass, but may be about completely rethinking the way we use glass in buildings, now that the solar furnace is almost as controllable as the gas or electric one.

More information at Sage Electrochromics.
Past Best of Shows at Greenbuild: (unlike Sage, all of which were extremely low tech)
Greenward Ridge Vent Turns Your Entire Roof Into a Solar Collector
GreenBuild: Agriboard Structural Insulated Panels
Prismaflex: A Simple Way Of Bending and Controlling Daylight

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Tags: greenbuild | Green Building | passive house