Self-Dimming Windows: Cooling Your House Without Killing the View

Remember when this was how you controlled glare and solar gain?

The 1960s birthed the era of astronauts, free love, and me (no connection that I’m aware of). It was also the decade that saw the invention of self-darkening glass, first seen in sunglasses. Last month I wrote about glass capable of generating electricity. But since the US Department of Energy reports 30 percent of heating and cooling energy is lost through windows, I’m going to continue to explore.  This time I’ve looked into types of films that can cut electricity costs while making interiors cooler and possibly window treatment-free.

The first of these technologies cuts UV radiation and offers privacy, but doesn’t darken the room. Called magic or privacy glass, these products are a sandwich of liquid crystals that turn glass from clear to frosted. Installation can be done at the factory when ordering new windows or after-market kits can be purchased and installed to retrofit. They require minimal electricity to run (although, counter intuitively, they consume power when clear, not shaded). After-market kits can be cut to most any window size. The largest sheets I saw offered by Home Depot were a pinch under four by ten feet and cost $3,410 each.

The issues I have this this technology are many. Claiming to eliminate the need for window treatments, these films only produce a frosted appearance. This means bedroom usage by anyone wanting to sleep past dawn is unrealistic. However those wanting to flick a switch for an unseen bonk may be satisfied. Second, they claim to reduce heat gain which should save on AC bills and yet I’ve not seen any hard numbers or calculations, which to be means savings are minimal.  Some users claim that the “at rest” clear setting can be cloudy instead of crisp (the clearest I saw had a 5 percent “haze” when clear).

On the upside, while in use they block nearly all UV light, reducing fading of upholstery and artwork. Also, it’s possible to turn some of these products from one-hit-wonder into a touchscreen tablet or movie screen. One maker touts their affordability, yet covering my living room windows would cost about $25,000, not including installation. For that kind of money I could replace the windows with a better option, and regardless, $25K equates to a lot of curtains.

I see these product’s best use as being where privacy or novelty is the main goal over darkness. Look for Sonte, and InvisiShade if this appeals.

The reason to have windows at all is to see out of them. Smart glass offers many more benefits over magic glass films.

Saint-Gobain’s self-dimming SageGlass used in Washington DC’s Dirty Habit restaurant

Smart Glass by View and Saint-Gobain

Photochromic glass was invented by Corning Glass in the 1960s and was first seen on those nifty eyeglasses your mom wore that became sunglasses outdoors. After fits and starts, Corning created the Serengeti sunglass brand (spun off many years later).

As with most technology, photochromic reactions got better. The first lenses took forever to return to clear when indoors and the higher the ambient temperature, the less dark the lens (great in winter, less great in summer). Manufacturing also got better. Originally, manufacturing required precision high-heat annealing of silver-halide crystals within the glass. For the past few years, companies have turned that very complex process into a film sprayed on during window manufacturing.

The result today is a glass that’s perfect for construction use.

Like the films above, photochromic glass requires electricity, estimated at a 60W light bulb for 2,000 square feet of glass. Also, instead of clear/frosted, you get actual tinting and room darkening (but it won’t yet substitute for blackout shades for vampires like me). The electricity controls the amount of tint.

Light can be manually or automatically controlled based on a number of factors including interior brightness, glare, and temperature. Imagine setting the desired brightness level and the windows automatically tint throughout the day to match. The results, report manufacturers, is an over 75 percent drop in solar gain and an average 20 percent reduction in energy demand. This equates to lower bills, but also means smaller, more efficient HVAC systems can be used. Part of the lowering of electric bills derives from the tinting itself. Because it doesn’t darken a room like shades, you’re not turning on lights as you would when closing blinds.

Also, unlike the frosted glass products, smart glass is available in a number of tint colors to match building aesthetics.

In commercial applications, DFW International airport was a recent guinea pig. Last fall, terminal A, gate 28 and Twisted Root burgers at gate A25 tested View Inc’s Dynamic Glass.  The results were astounding. Seats and carpet behind the glass were 10 to 15 degrees cooler. People stayed longer in the cooler location and specifically spent more money at nearby shops. Twisted Root reported an 80 percent increase on booze sales over the prior year. This resulted in alcohol increasing to 17 percent of revenues from eight percent the year before and nine percent the month before.

Translated into non-alcoholic terms, photochromic glass has a big impact on solar gain and glare which translates into increased indoor comfort. Since the trial ended, DFW International approved $25 million to buy more Dynamic Glass to cool its worst-offending glass walls.

View’s main competition seems to come from France-based Saint-Gobain who has been in the construction materials business for 350 years. They purchased New York-based SageGlass in 2012. Founded in 1989, they were the first to develop electrochromic architectural glass (versus Corning’s optical glass) that has now been installed in 27 countries.

EXO at Excelsior Parc in Reston, Virginia

Within residential, the ball is just starting to roll. View is supplying glass for a 16-story, 467-unit apartment building in Reston, Virginia (seen above). One thing residential uses offer is uniformity. Residential buildings have all manner of blinds, shutters and curtains that often create a “clothes hanging on the line” appearance. Along with the energy benefits, residential buildings would offer a more uniform exterior, generally classing up the place.

Wondering …

I wonder if this type of electrochromic glass can be used in conjunction with the electricity-producing glass I featured last month?  Think about it. Neither one is 100 percent effective so while the outer pane generates electricity, the inner pane could be electrochromic (dimming based on energy not turned into electricity). In combination, you’d gain the electricity generation with the added finesse of being able to control the amount of light and heat entering the room.

Given the newness of the electricity-generating glass, it may be some years before the two technologies are brought together.

Hindrance …

The one big hindrance to either technology is the difference between who builds and who pays the electricity bill. The developer is largely uncaring about boosting energy efficiency as tenants will be the ones ultimately footing the electricity bills. I think it’s up to a third party, likely government, to step in and craft guidelines that foster the greater good of power generation and energy efficiency. In fact, nearly all the case studies I’ve read highlight customers who built purpose-built buildings for their own use and so utilized these technologies to help themselves.


Remember:  High-rises, HOAs and renovation are my beat. But I also appreciate modern and historical architecture balanced against the YIMBY movement. In 2016, 2017 and 2018, the National Association of Real Estate Editors recognized my writing with three Bronze (2016, 2017, 2018) and two Silver (2016, 2017) awards.  Have a story to tell or a marriage proposal to make?  Shoot me an email Be sure to look for me on Facebook and Twitter. You won’t find me, but you’re welcome to look.


2 Comment

  • “…an unseen bonk….” Good one.

  • Some form of a “flip a switch” frosted glass/clear glass was installed in 2007 in the Fearing’s Restaurant Wine Room at The Ritz-Carlton, Dallas. It’s a fun feature, but nothing about conservation or preservation.
    Going forward, I think the electrochromic glass would be a feature a condo buyer in a new building might be willing to pay for, especially in west-facing windows and perhaps bedrooms. Being a high rise resident, I love this idea.