In order to achieve carbon neutrality by 2050 and to respond to the climate change emergency, it is necessary for University of Washington to invest in new building technologies that can reduce building energy consumption while at the same time improving the student experience and supporting the institutional mission of the University. Buildings are responsible for over 40% of carbon emissions in the United States. Building heating, cooling, and ventilation (HVAC) and lighting use well over 50% of Campus building energy. Electrochromic windows have the potential to reduce energy consumption in all of these areas and potentially reduce the cost and size of building mechanical systems when incorporated as part of an integrated design process.

ECWs are an optical glazing (window) technology by which the visible and solar transmittance of a window can be controlled between a transparent state to a very darkened state thus providing a range of visible light transmittances (Tvis) and solar heat gain coefficients (SHGC) when modulated by a control system and sensors to adjust to climate conditions. By dynamically responding to local climate and immediate solar conditions, as well as real-time internal conditions within a building, electrochromic windows control the amount of heat and light emerging a space, while reducing glare and improving access to views outside.  EC glazing is made five layers of ceramic material coated onto a pane of glass.  A small electrical current is sent through the ceramic coating which causes lithium ions to transfer the ceramic layers. The tint within the window pane is the result of this process.  Reversing the direction of the polarity allows the window pane to clear.  Window tint percentage can range anywhere between 0% and 99% for increased glare and heat control.  The tint system may be occupant controlled or set to automation using a control system in which the system can be intelligently optimized to reduce heat and glare issues. The inclusion of ECWs can eliminate the requirement for mechanical building blinds or shades, facilitating glare control and space darkening for audio visual displays.

In a study conducted by Lawrence Berkeley National Lab, ECWs have shown measured building cooling load reductions of 19-26% and lighting power savings of 48%-67% when combined with photo-responsive lighting controls. The saving potential varies by building type, use, and climate zone, due to variability in heating and cooling loads, solar exposure and glare control requirements. For this reason ECWs are frequently modulated by controls that adjust visible and solar transmittances by window or facade to reduce whole building energy consumption and maintain visual comfort.

More importantly, and number of studies, most notably by Lisa Heschong with the Heschong Mahone Group, have correlated access to daylight and views with significant improvements in student learning. A growing body of photo-biological research shows that occupants experience many positive physiological results when being exposed to natural daylight and to outdoor view.  Naturally-lit environment has values of triggering positive responses within human’s endocrine system. Wellness benefits are range from mental clarity, visual acuity, or even regulation of body system for better sleep. Although traditional blinds or curtains also provide lighting autonomy to the occupants, typically the devices are regularly left closed for extended periods, which results in reduced access to daylight and view. The weather-responsive controlling mechanism and the flexible light transmittance of EC glazing exclude the concerns led by manual-control operation, and potentially reduce the cost of maintenance.