The Health and Design Benefits of Accessing Daylight and Views with Dynamic Glass

A closer look at how electrochromic glass provides healthy, productive, and controlled daylight exposure without compromising energy performance
[ Page 8 of 9 ]  previous page Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 next page
Sponsored by SageGlass
Jeanette Fitzgerald Pitts
This test is no longer available for credit

Transmitting Daylight and Preventing Solar Heat Gain

EC glass is able to allow more visible light into the interior, while simultaneously providing more protection against heat gains than many of the other types of glazing currently available. Illustrated in Figure 1, when comparing the SHGC of different types of glazing at identical VT levels, EC glass provides better protection from solar heat gain than reflective glass, tinted glass, and tinted low-e glass.

Figure 1: EC glass performance compared to static glass products.

Image courtesy of SageGlass

Figure 1: EC glass performance compared to static glass products.

Balancing Act: Daylight Control and Quality Daylight Admission

As previously mentioned, the physiological and psychological benefits of daylight exposure are directly linked to a person experiencing the time-appropriate increases and decreases in levels of daylight and the natural shift in the color of daylight that occurs throughout the day.

When EC glass is fully clear, it does not impart a significant color shift to the daylight transmitted through it. However, when the EC glass tints to manage glare and solar heat gain, the tint is a blue-gray, which imparts a color shift in the daylight passed into the interior and significantly changes the color rendering in the space.

However, effective control of EC panes on a facade can provide a daylit space in which the color of the light is not significantly changed from that of the incident daylight and has good color rendering. Recent studies of EC glass, conducted by Professor John Mardaljevic et al., and summarized in the whitepaper How to Maintain Neutral Daylight Illumination with Electrochromic Glazing, have proven that the quality of daylight transmitted through EC glass remains essentially neutral as long as 10 to 15 percent of the EC glass pane remains in its highest transmittance state. This is because the majority of light reaching the interior has been transmitted through the panes at 60 percent VT. The rest of the glass area only lets one percent of the light through and thus, even though it is blue, the light transmitted through these sections of the facade only makes up a small portion of the daylight transmitted and is not enough to change the overall light color significantly. Mardaljevic’s findings indicate that a neutral and honest rendering of the color of daylight can be achieved even if the majority of the EC glass on a facade is fully tinted.

This blend of tinted and highly transmitting glass on a facade can be achieved in two ways. Whole panes can be grouped and controlled separately in zones, or segments within a single pane can be independently controlled, a functionality referred to as in-pane zoning.

In-Pane Zoning

In-pane zoning refers to the ability to apply different degrees of tint to defined areas within a single pane of glass. Essentially, the single pane can be divided into up to three uniquely controllable segments where the level of tint for each segment can be independently controlled. This is an essential feature in floor-to-ceiling glass panes, as it improves the flexibility of the glare and heat gain control that the glass is able to provide, while permitting ambient daylight into the space and maintaining the integrity of the light’s color quality.

Example of in-pane zoning of EC glass, which is necessary to appropriately balance the competing needs of glare control, daylight admission, energy performance, and light color quality.

Photo courtesy of SageGlass

Example of in-pane zoning of EC glass, which is necessary to appropriately balance the competing needs of glare control, daylight admission, energy performance, and light color quality.

Here is a practical example of how in-pane zoning works in a floor-to-ceiling window and the benefit it provides. During the day, when a window receives an intense, direct beam of sunlight, the specific area receiving the exposure tints to the lowest VT of one percent, managing glare. The remaining portions of the glass pane remain at higher transmissions, allowing the available diffuse daylight into the space and achieving the necessary ratio to maintain a neutral color quality on the interior. By contrast, blinds and shades deploy from the top, blocking all of the daylight at the pane, even if the direct beam is only incident upon the view portion of the glass.

Differentiating degrees of control within a pane of glass offers designers a better solution to promote daylight penetration, while preventing glare, than conventional blinds and shades.

 

[ Page 8 of 9 ]  previous page Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 next page
Originally published in Architectural Record
Originally published in December 2015

Notice

Academies