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.
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 was an assistant editor of BUILDINGS.
Lory Student Center, Colorado State University
Facilitating the needs of more than 20,000 people passing through on a daily basis, Colorado State University’s Lory Student Center is a 160,000-square-foot structure that underwent a $72 million renovation to update HVAC systems, expand the building and improve energy efficiency, which included the installation of electrochromic windows.
In the student center’s roughly 14,000-square-foot ballroom, the university was looking to make the facility more energy-efficient and more attractive to prospective clients who rent the space for events. However, this was difficult in Fort Collins, a city that experiences 300 days of sunshine every year.
To solve these issues, Colorado State enlisted the services of View, a smart glass company located in Milpitas, CA. Brandon Tinianov, vice president of business development at View, explains, “You have high solar exposure in a mixed dry climate environment in that high desert plain in Colorado. On a clear day, there’s going to be a massive solar heat gain coming into that room, so we wanted to minimize energy consumption and discomfort.”
In addition to the energy goals that the windows would bring, the university wanted to showcase its scenic view. “The windows face west and overlook the Rocky Mountains, so we were looking for a solution that maintained that view, but was also able to control daylight for events and the sun glare in the late afternoon as it goes down over the mountains,” says Jason Rogien, assistant director of event services at CSU.
Prior to the installation of electrochromic windows, the ballroom windows were covered by cumbersome curtains that blocked out the sun.
“Before renovation, we just had curtains that were constantly breaking or needing repair and upkeep, so we wanted to get rid of them,” explains Rogien. “We were looking for something that was going to provide us energy control and savings.”
Not only were the curtains unreliable in controlling the sunlight that entered the ballroom, but they almost always needed to be closed completely, which obstructed the view that the university wanted to put on display.
“The curtains were almost always closed in order to use any kind of AV for an event, which pretty much everyone does because you don’t want any sunlight coming in on the screen,” says Rogien. “Now, if we tint the glass all the way, we can do just about anything in there.”
The windows in the ballroom have four tint levels that are adjusted in three different ways. The first mode is through an automatic control. This depends on current conditions and will adjust to the amount of sunlight entering the space.
The second is scheduled, which automatically adjusts as they day progresses and the sun comes through the west windows. The third is manual, allowing the space’s occupants to select the setting that best fits their needs.
Because the electrochromic windows face west in one of the sunniest cities in the U.S., they provide energy savings for the building.
The massive renovation project makes it difficult to establish the exact savings from the windows at this point, but there has been a noticeable improvement in how they have stabilized the influence of solar heat during all seasons within the facility.
In addition to the energy savings, the university has found that the electrochromic windows can be a source of revenue. They are able to divide the ballroom to rent out for events, and the ability to see the campus and the Rockies while also being able to facilitate the AV and other needs for the event itself has made the section with access to the windows popular among clients.
Rogien explains, “Our clients love being able to have that view, so we charge a premium to use the ballroom with the glass because there’s such a demand.”
Rogien is also quick to note that the windows haven’t required much maintenance since their installation. They have worked consistently and are expected to last the lifespan expected of a static glass window.