There is now indisputable evidence of the positive benefits of access to daylight on human health and well-being [1]. Access to daylight has been shown to significantly improve productivity and reduce absenteeism in office settings, increase student achievement in schools, and increase healing rates in healthcare environments [1]. It turns out that views to the outdoors may be even more important than daylight (although hard to separate). In fact views of nature, specifically, have been shown to reduce stress levels and improve mood [2]. The World Health Organization says that mental health disorders are expected to be the number two illness worldwide by 2020, and stress can be a major contributor [3]. Providing views of nature and access to daylight within the built environment is therefore an important, some would say, vital design factor in 21st century buildings. However, the provision of more glazed area to provide daylight and views can come with unintended consequences for occupants in the form of thermal and visual discomfort. This is often due to the fact that the solar heat and glare that accompanies daylight are not effectively managed primarily because the conventional static building envelope cant respond to the ever-changing exterior environment. In fact, studies have shown that the presence of glare and thermal discomfort completely negates any of the positive benefits of daylight and views [4, 5]. Even if manual blinds are used to control the glare, they tend to be left down long after the glare condition has passed, blocking the views and daylight admission and negating the positive benefits of the window. Electrochromic (EC) glass is a very effective solution for creating healthy and productive spaces because it can allow designs that provide greater access to daylight, maintain views at all times, and do so without the negative impacts of thermal discomfort and glare. The wide dynamic range of EC glass (60 to 1% visible light transmission and 0.41 to 0.09 solar heat gain coefficient) (figure 1) provides architects with unprecedented energy and heat and light control performance that allows the use of more glass without energy or comfort penalty. In addition to downsizing HVAC systems, by reducing peak loads as well as overall energy use, EC glass can also enable the adoption of new more efficient and comfortable heating and cooling systems, such as radiant heating and cooling and chilled beam systems. The next generation of EC glass provides even more design freedom to architects through improved color aesthetics and color choices which are now available to complement various design schemes. The first generation of EC products on clear glass have a green/yellow/red exterior aesthetic, whereas the new generation of EC glass has an attractive slightly reflective blue-green aesthetic that complements a number of the standard low-e and solar control products available (see figure 2 below). Moreover, additional color choices are available such as green, blue, gray or bronze to provide more architectural design freedom. 
Figure 1: EC Glass performance compared to static products. 
Figure 2a: Generation 1 EC glass with yellow/green/red aesthetic (inside the box) with typical low-e with blue reflection elsewhere on the fa̤ade. 
Figure 2b: Generation 2 EC glass with improved blue/green exterior aesthetic, more typical of low-e glass product. As EC glass size availability has increased to provide panes that extend fully from floor to ceiling with no mullions (5x10), the ability to segment the pane into 3 independently controllable zones has become essential to ensuring the optimum balance between controlling glare (1% visible light transmission required) and achieving sufficient daylight admission, light color quality and energy performance (see figure 3). If the whole pane from floor to ceiling had to be tinted to 1% visible light transmission to control direct sunlight glare, the interior space would be too dark, and the light color rendition would be too blue. Only a small amount of the EC glass need be in the clear state to achieve neutral color rendering even if the remainder of the glass is fully tinted. For this reason it is very important to zone the EC glass appropriately to achieve the desired occupant comfort. 
Figure 3: Example of in-pane zoning of EC glass. With improved aesthetics, color choices, and larger glass sizes with zoning options that do not compromise interior daylight admission, EC glass provides an elegant dynamic solution to a dynamic heat and light control problem. By providing flexibility in using more glass even on the more challenging east and west orientations, architects have more freedom to design with glass and meet the challenge of designing a well day-lit, comfortable and healthy building that does not compromise energy performance. Submitted by Terry Vaughan, Vaughan Architectural Products Written by Helen Sanders, PhD. SAGE Electrochromics, Inc.
References:
[1] ÏHealth, Wellbeing and Productivity in Offices, World GBC Report 2014. [2] The Economics of Biophilia: Why Designing With Nature in Mind Makes Financial Sense (2012). Terrapin Bright Green LLC. [3]http://www.who.int/mental_health/advocacy/en/Call_for_Action_MoH_Intro.pdf [4] Heschong Mahone Group (2003), ÏWindows and Offices: A Study of Worker Performance and the Indoor Environment (technical report) for California Energy Commission. [5] O. Seppanen et al., ÏEffect of Temperature on Task Performance in Office Environment, LBNL report 60946.
Google+