Electrochromic glazing

Hi Kim, I recently (past few years) worked on a project near Philadelphia with a large volume of electrochromic glazing. I can comment on some of your questions: 1) What does it do to the quality of occupant experience when the glazing goes all the way down to the lowest visible light transmission levels, only allowing maybe 2-4% of visible light into the building. Are occupants comfortable in that environment?  When the glazing is all the way tinted, it feels like dusk, where the sky outside appears a twilight blue. On a hot day, the combination of blue color and SHG reduction does make it feel cool to occupants inside. In a big room or atrium, the daylight is still bright enough to work by, but with a lower window/wall ratio, it may be dim enough that electric lighting is required in an otherwise daylit space. Our client wanted the glazing primarily for glare control. 2) If the client were to choose not to allow the glazing to run the full dynamic range of visible light transmission and corresponding SHGC (due to occupant preference), is the operational energy savings lost? I’m not clear on the details of choosing the range of VLT, but in our energy modeling five years ago, we did not find that electrochromic glazing substantially reduced cooling loads. That was a bummer, as we had been hoping to use reduced operating energy to offset embodied energy (and energy costs). However, it did help shave peak loads, and it eliminated the need for interior operable shades. 3) Embodied carbon in electrochromic glazing appears to be an order of magnitude greater than in a standard IGU. I've found one paper so far that seems unbiased and indicates the operational carbon savings can offset the embodied carbon. I'm curious if anyone has found other information about the embodied carbon implications. We didn’t have this data at the time – I suspect the embodied carbon footprint is very large, which would honestly give me pause in specifying it today. However, maybe you could look at the manufacturing location and see how clean the grid is in the area where you would be sourcing your glass from? That would probably make a big difference in terms of carbon footprint – others may know more. 4) For budget purposes, there is discussion of using electrochromic in some areas but not others (standard glass on the north facade, for example). If anyone has experience with that, I'm curious if it looks strange aesthetically if both types of glazing are visible from some vantage points. We considered standard glass on the north façade, and then on just the lowest panes of the north façade, to reduce cost. Long story short, I think that could work IF you will never see tinted and untinted glass in the same room, juxtaposed against each other. When they are adjacent, it ends up looking like the untinted glass is a malfunctioning window instead of deliberately untinted. Even at the least-tinted setting, the tinted glass has a very different tone. Hope this helps. Feel free to reach out if you have other questions.

We’ve used electrochromic glass on a few projects. While the way the Sage or View presented the glazing as able to be dimmed along a whole spectrum, in programming the controls, their software only allowed us to set the glass at a maximum of four VLTs – so incremental points as opposed to the whole spectrum from your starting VLT to fully darkened. Just adding this information to the information provided by others. Fro

We too have used electrochromic glazing in a few projects – mostly in skylights. I am still not a fan but hope to be shown how it is working better by this group. For context: We tested an older version of View in our offices with West and South exposure (2018ish). It wasn’t good. To be fair, it was installed over existing glass as a temporary test to show ourselves and clients. Mostly two items: 1) the reflectance was distracting (think mirror) and 2) the blue was uncomfortable – especially if you are facing it. We have one renovation project (tilt up with existing 18” glass slots, open floor plate at about 35K feet) where the switch from standard glass to electrochromic was ok – meaning the users didn’t mind it. I think the small width had something to do with it. Other project analysis done with great daylighting consultants helped to create graphics that showed the experiential forecast along with energy savings. That helped a lot. Thinking about blue surfaces , especially in art classrooms, helped our client think differently about the benefits. We then were able to convince them to go with exterior automated shades. Again, interested in hearing if there are good stories out there From: Lois