This is part 3 of a 3-part blog post series on biophilic design and associated resources. These blog posts complement our recent educational webinar on biophilic design.
Daylight Distribution
Living, studying, and working in spaces that are well-daylit is an experience that ought to be more common. With few exceptions, we humans respond well to such an environment, increasing productivity, satisfaction and delight. It’s not just daylight quantity that’s needed to provide these benefits, however. The spatial distribution and frequency of daylight must also be right. For example, most projects we see rely on windows to admit daylight into the space from the side. Although side-lighting is typical, it’s actually very challenging to ensure that people 40 feet from the window enjoy daylight benefits without cooking the eyeballs of those right next to the windows. In terms of biophilia, the view-providing power of windows is perhaps more important than their daylight potential. In TSP’s new office space, we faced this challenge head-on, sticking with it until we succeeded.
Prospect and Refuge
One of the strongest biophilic concepts is that humans deeply favor both prospect and refuge in the places they tend to occupy. In a daylit space, the windows can provide prospect, but if there is frequent glare from daylight, it’s not much of a refuge. As we planned the south studio’s solar control, we evaluated several options using annual daylight simulations. Balancing open views, plentiful daylight, simplicity, and reasonable cost, we selected lightshelves and a perforated film on the lower window sashes. Keep in mind this is a fit-out and we could not change the windows or add exterior solar control. After moving in, people working in the south studio objected to frequent, large pools of bright daylight on sunny days. Even though the perforated film reduced the illuminance of these pools from 1,000 footcandles to 300 footcandles, the contrast became nearly unbearable, and so frequent that we had to re-evaluate our solar control intervention.
Didn’t our simulation show that we were OK? Looking back, while our interventions greatly improved the baseline condition, the spaces were at the borderline for acceptability for the Annual Sunlight Exposure metric; 7% for the south studio. Although we mocked up the perforated film before installation, we overestimated its effectiveness in diffusing direct beam sunlight deep into the space. The perforated geometry that allowed legible view through the film also projected crisp images of sunlight into the space. We had the prospect but not the refuge. In the mean time, colleagues made their own interventions to allow comfortable conditions. In the image below, paper on the windows provides refuge at the expense of the prospect.
Could we have both protection and view? We mocked up venetian blinds on the middle window’s lower sash to test whether that could work. Over three months, we monitored the view and shading performance and got used to the look. These blinds are a far cry from the cheap mini-blinds we all know. They are engineered by Retrosolar in Germany to provide all of our hopes and dreams. The product is called Retrolux 50mm, with slat height and angle controlled by turning one rod at each window. Each slat is folded to reflect shortwave energy back outside and selectively reflect daylight up onto the ceiling. In person, somehow this folded geometry makes the slats disappear more than typical 2” blinds. A common solution in this situation would be manually-controlled roller shades. If feeling fancy, an automatic control system could be added, but would have required difficult wire routing in our case. We have roller shades in other parts of the office and the view through the fabric is not as clear as it is through the blinds. It’s commonplace for manual shades to be lowered to deal with a transient glare condition and left lowered for years. This provides refuge but no prospect. In the end, we decided both the shading and the view through the blinds was superior to roller shades and moved forward with that.
Retrolux 50mm blinds have a cutoff angle of 28° with polished top surfaces. Most 2” blinds have a cutoff angle of 45° by contrast.
Finished installation
The blinds are left down as shown, where they provide enough protection most of the time. In those rare cases in winter, affected users will occasionally tilt the slats up to completely block the solar disk. One measure of success is whether it needs high-end sensor input to operate year-round. This solution keeps it simple and gets the results.
Simulation Advancement
We were fortunate that as we began to re-evaluate this problem, Climate Studio daylight and glare software added an incredible tool to predict glare. Our early studies looked only at the strength and frequency of direct daylight falling on a horizontal work surface. This metric is called Annual Sunlight Exposure. While a powerful tool, it doesn’t directly measure the brightness as viewed by people as they occupy a space. The annual glare tool places multi-view sensors throughout a space and predicts how frequently glaring conditions will occur from those points of view, in those directions. Viewed as “flowers” spread across the floor, the problematic positions and view directions immediately become apparent. This tool helped us quickly verify that our solution would work.
Glare probability with lightshelves and perforated film. The camera icon is pointing toward the south studio we’ve been discussing.
Glare probability with venetian blinds. Note how much less red there is in the south studio.
After installing the blinds, we frequently checked in with south studio occupants informally. Two years after installation, we completed a formal post-occupancy survey and found that occupants were quite satisfied with the blinds. Now we have both the daylight benefits and those of open views, connecting people from across the room with the treetops and human activity happening outside our space.
Biophilic Design Resources
- Biophilic Design: The Theory, Science, and Practice of Bringing Buildings to Life By Stephen Kellert
- Biomimicry: Innovation Inspired by Nature By Janine M. Benyus
- Creating Biophilic Buildings By Amanda Sturgeon and Juliet Grable
- 14 Patterns of Biophilic Design: Improving Health & Well-Being in the Built Environment By Terrapin Bright Green
- Biophilic Design Guidebook by Living Futures
- Biophilic Design Toolkit by Living Futures
TSP is ready to support biophilic design education, inspiration, and guidance on your next project. We are constantly looking for ways to innovate, inspire, and provide better quality high performance green buildings.
