In the first segment we started with basics of daylighting design and how dynamic glass fits into daylighting strategies. The second installment delved into zone tinting within a curtain wall of electrochromic glass. This final post explores how electrochromic windows can be controlled to improve the quality of light.
In my previous blog post I talked about how having multiple zones in electrochromic glass can provide much more precise control of the tinting to optimize daylight and control heat gain in a building. But there’s another important benefit that comes with finer-grained control of the glass: the quality of light entering a building.
Quality of light is important because it impacts how people experience the space where they live and work. At the right intensity and color levels, light quality can create a more pleasant and productive environment for occupants. And when done incorrectly it can create an unbalanced ambiance.
Our eyes see light in a very small region of the electromagnetic spectrum called “visible light,” which corresponds to a wavelength range of 400 – 700 nanometers and a color range of violet through red. Some refer to this range as the color temperature. Getting the right balance in color temperature is important because it can impact things such as relaxation or our ability to concentrate. Light transmitted through a tinted piece of electrochromic glass will shift toward the lower 400 nanometer wavelength end of the spectrum. But when we apply effective zoning strategies we can achieve color mixing to attain a more neutral color. Even allowing a small amount of clear light to pass through an otherwise fully tinted window can achieve this goal.
For instance, if you have a low-angled sun problem on a facade you can tint the lower three-quarters of the glass zones down to 1% of visible light transmission while keeping the remaining upper section clear. Even though you’ve dramatically reduced the total amount of light entering the space, and its attendant color range, most of the light enters through the clear zone and you end up with a flat, balanced distribution of light wavelengths transmitted into the space. Additionally, this zoning strategy is the only way to maximize the daylight entering the space. Conversely, a lack of zoning will block the natural light entering the space and require additional artificial lighting.
Consider the case of Chabot College in Hayward, California. The architect of a new Community and Student Services Center (CSSC) wanted to incorporate as much glass as possible into the building to flood the interior with daylight and keep a connection to the outdoors for the well-being of the students, while also achieving LEED® Platinum certification. The building was designed with an atrium that included a two-story, south and west facing curtain wall, which posed significant glare and heat control challenges from the sun.
SageGlass was used on the south and west facing facades to create a six zone curtain wall that was integrated into the building management system. The glass darkens or clears by zone based on set air temperature thresholds, with a manual override for additional adjustments. Temperature is controlled by radiant heating and cooling in the concrete slab, combined with roof and ceiling air scoops for natural ventilation. In addition, no forced air HVAC system is required for the CSSC atrium. And the balance of color temperature achieved with multi-level zoning created a comfortable and inviting environment for the students and faculty.
With this kind of control, more natural light penetrates the core of the building while blocking unwanted heat and glare. This ability to manage these three, sometimes contrary factors – heat gain, daylighting, and glare control – coupled with the ability to provide neutral color rendering within the space, creates a much more pleasant environment for building occupants.