As great as it is to have natural light illuminate a building, daylighting can have its fair share of drawbacks, including two that are not always anticipated. If windows are clear, they can let in too much sunlight, jeopardizing comfort and energy efficiency.
According to the Department of Energy, sunlight can increase cooling loads by 20%. Glare can make it difficult to see computer screens and other monitors, causing occupants to pull blinds, which negates the benefits of having natural sunlight enter a building.
With the World Green Building Council (WorldGBC) reporting that green buildings facilitate greater productivity and commercial benefit while also being more sustainable and efficient, products that fulfill both environmental and workplace comfort issues become more advantageous. Electrochromic windows – those that can adjust their tint electrically – might be an option to help, as they influence comfort and lighting, which are two of the most important environmental factors contributing to an employee’s well-being at work, according to WorldGBC.
Electrochromic windows have emerged as a solution for both lighting and comfort as they are dynamically adjustable, letting in varying levels of sunlight during the day. Their market is expected to grow from $2.34 billion in 2015 to $8.13 billion by 2022. But what are electrochromic windows, and are they right for use in your facility?
How They Work
"Electrochromic windows, as you might be able to tell by the name, require electricity that causes a chemical change to take place in a microscopically thin coating that causes the material to absorb the light, which we see as tinting,” says Lou Podbelski, Vice President of Architectural Solutions at SageGlass, an electrochromic glass manufacturer in Faribault, MN. “That stops glare and also prevents solar heat gain from entering the building. It’s actually rejected back out.”
In order to catalyze this change, the glass requires a small DC voltage. While this energy usage is minimal, the exact amount of energy required to change the window’s opacity varies depending on busbars, or the small strips that carry the charge and change the window.
The amount of power that is necessary is very small. Brandon Tinianov, Vice President of Business Development at View, an electrochromic glass manufacturer in Milpitas, CA, says, “We will inject a small voltage – about 2 volts – for the glass tint to change. Once the glass is in that tint state, there’s almost no voltage required. This is a very, very low consumption device.”
At the Lory Student Center at Colorado State University, the windows change tint settings three times a day, which, in the entire complex, is roughly as much energy consumed as a 100-watt lightbulb over the same period, according to Tinianov.
“If you have a wide piece of glass, it would be a little more time-consuming to switch than something half that size,” says Podbelski. “It’s a function of the size of that glass and its temperature.” He notes that the typical timeframe to change glass from its clearest state to the darkest state is roughly 15 minutes, but because they are conventionally set for automatic changes between these extremes, the transition is more gradual and takes less time to change from state to state.
Most manufacturers present four tint settings, but Tinianov explains that the technology does not prevent them from developing more – it’s just simpler and more effective to have four. These settings are based on light transmission through the glass. For example, SageGlass comes with tint states of 60%, 20%, 6% and 1%. When the window is clear it is at 60%, and the most darkly tinted setting is at 1%, creating a logical progression down to a setting of no glare.
Podbelski admits that 1% might seem to be incredibly dark, but that isn’t actually the case: “When you’re looking at the amount of light that is outside and what you need inside, it’s really nothing. You can have enough light inside with 30 to 50 footcandles, and there’s 10,000 footcandles on a bright sunny day. So you can see that 1% seems like it would be extremely dark, but in actuality it’s still letting in some light.”
Feasibility of Electrochromic Windows
New technology isn’t always feasible to install in your building. Prices vary in electrochromic windows, but they do provide energy savings. As the technology progresses, it will likely continue to become more affordable and more widely adopted.
Earlier this year, Sen. Edward Markey (D-MA) introduced legislation that would make electrochromic windows more affordable for prospective buyers. The Electrochromic Glass Act of 2016 would amend the tax code to “ensure that electrochromic glass qualifies as energy property for purposes of the energy credit.” The bill has yet to be passed, but if signed would mark an important sign of recognition from the federal government and may make purchasing them easier.
This brings up a couple of important questions. Are electrochromic windows a feasible solution for retrofits? Or are these only really practical in new construction projects?
“The use of dynamic glass in buildings is the same as replacing windows with standard glass in existing buildings,” says Tinianov. “It’s going to be at the same cost as replacement with low-e glass. One of the reasons that low-e glass isn’t installed into legacy, single-pane glass is because it saves an incremental amount of energy, but not a profound amount, and dynamic glass can reduce that energy consumption by significantly more.”
For these reasons, electrochromic glass is a major investment, but it will help you save on energy at a greater rate than any other glazing solution available. Moreover, the ease of installation, which is more or less the same as typical window installation, makes them a reasonably practical retrofit solution.
“The retrofit market is larger than new construction given the number of buildings that were produced back in the ‘70s and ‘80s and even before that – where the building was state of the art and no longer is,” Podbelski explains. “The building’s just not up to par in terms of energy efficiency or how it makes people inside the building feel.”
These retrofit applications are not limited to older buildings. Podbelski notes that a considerable number of newer buildings receive electrochromic windows because FMs find that there is a problem with the static glass installed during construction and want to remedy that quickly.
The expectations of the rapidly expanding market and the growing practices of electrochromic retrofits are lining up with greater emphasis on workplace comfortability and energy efficiency. It might be difficult to predict exactly how electrochromic technology might manifest, but it seems reasonable to believe that it will.
Justin Feit email@example.com is assistant editor of BUILDINGS.