Photo by Sean Airhart courtesy NBBJ

Early this year, Amazon commemorated the opening of its Seattle Spheres, the showpiece of its burgeoning headquarters designed by Seattle-founded NBBJ. The three nested glass bubbles containing some 40,000 plants from over 30 countries at the base of Amazon’s Tower II serve as an iconic gathering spot and ancillary workspace for company employees and the “new visual focus and ‘heart’ ” of the company’s Seattle offices, according to a Popular Science article. The unusual programming of the building for both plants and people signifies a remarkable advancement in conservatory architecture with intriguing future implications.

The conservatory model traces back to the 16th-century Italian limonaia, or lemon house, a simple brick shed devised as a protective winter shelter for citrus plants. Orangeries emerged further north in Europe with the same purpose, endowed with tall apertures oriented to maximize solar exposure. These structures were not markedly different from other styles of residential construction at the time.

However, the Industrial Revolution brought about technological achievements in iron and glass that led to a new form of architecture. Buildings such as the Palm House at Kew Gardens in Richmond, England—a sizable structure consisting of wrought iron and hand-blown glass panes—provided a growing community of explorer-botanists with a viable artificial climate in which to cultivate plants sourced from far-flung regions. This ferrovitreous architecture, which made the most of light and heat from the sun, thus prioritized plant survival over human comfort.

A café area for gathering
Photo by Bruce Damonte courtesy NBBJ Café area in the Seattle Spheres

In the following century, the scientific investigation of conservatory plants expanded to include the buildings themselves. Buckminster Fuller popularized the notion of an artificial biosphere, made iconic by his geodesic dome for the Montreal World Expo in 1967. In 1991, Space Biosphere Ventures took this concept a step further with the Biosphere 2 project in Oracle, Ariz., to test the first completely self-contained artificial biosphere. The glass-and-steel space frame structure housed plants representing seven different biomes—including a rainforest, mangrove wetland, and savanna grassland—and was designed to be completely airtight. Unlike the early glasshouses, which were ventilated and could be visited freely, the Biosphere 2 functioned as an experimental surrogate Earth, trapping its volunteer occupants inside a closed system. Its two well-publicized experiments were hindered by food and oxygen shortages, plant subsidence, and sociopolitical conflicts, according to Pushing the Limits: Insights from Biosphere 2 by Mark Nelson (University of Arizona Press, 2018).

But if the 20th-century biosphere represents the fruition of a contained ecosystem for scientific inquiry, the 21st-century version adapts the model to a broader range of human activities. What is significant about the Amazon building is that it is first and foremost a workplace. “The Spheres are a place where employees can think and work differently surrounded by plants,” declares Amazon’s website devoted to the project. “The Spheres are a result of innovative thinking about the character of a workplace and an extended conversation about what is typically missing from urban offices—a direct link to nature.”

Greenery inside the Amazon's Seattle Spheres
Photo by Sean Airhart courtesy NBBJ Greenery inside the Amazon's Seattle Spheres

The experience is convincing. During a recent tour led by NBBJ senior associate David Sadinsky, I was impressed to see Amazon employees typing on laptops, making phone calls, and engaged in lively group conversations—surrounded by lush, verdant foliage and sunlight. Who wouldn’t choose to work in this kind of environment, particularly during Seattle’s gray winter months? The regulation of the indoor climate such that the Spheres can function as an effective long-term work environment is a critical achievement.

Alternative seating areas and pathways
Photo by Bruce Damonte courtesy NBBJ Alternative seating areas and pathways

For the Spheres design team, the key was to align the long-term occupancy needs of both humans and plants. “In order to quantify our goal, we used a psychrometric chart to discover what people find comfortable,” Sadinsky says. By overlaying the environmental conditions of various plants with the acceptable range of conditions for human comfort, the team determined that high-altitude equatorial plants occupied the sweet spot of the intersection.

“We found the mid-montane ecosystem overlaps with human comfort range and contains a botanical collection that spanned the globe, telling an interesting story of diversity that is also visually interesting,” he says. “The overlapping of the comfort zone and botanical need became the very narrow bandwidth for the operating environment during occupied hours.”

Equally important is the building enclosure design. One of the challenges in the biosphere model is inadequate sunlight for chlorophyll production, which can lead to etiolation—suboptimal growth—in plants. In Biosphere 2, for example, light levels were reduced by the bulk of the space frame and internal shading mechanisms. Because typical low-E glazing is effective in reducing heat gain but insufficient for chlorophyll absorption, Seattle Spheres designers needed to determine a way to mitigate solar heat gain without compromising plant growth.

Undeterred, the team championed the development of a “clear low-E coating for low-iron glass that is both able to reject the visible light spectrum that contains the most heat while still allowing for daylight to penetrate inside for photosynthesis,” Sadinsky says. This assembly both encourages photosynthesis and limits temperature increases cause by the sun.

Psychrometric chart detailing the overlapping conditions for optimal plant growth and human comfort
Provided by NBBJ Psychrometric chart detailing the overlapping conditions for optimal plant growth and human comfort

Unlike the angled Biosphere 2 space frame, the Spheres glazing is supported by prefabricated steel modules that form structurally efficient spheroidal domes, delivering ample volume with minimal surface area. The module geometry—a pentagonal hexecontrahedron—is both practical and symbolic, permitting large-scale prefabrication while recalling molecular structure configuration. Architecturally, the three domes function as a single conjoined skylight that bathes occupants in illumination without excessive glare.

Given the success of the Seattle Spheres in optimizing the needs of both plants and people in a daily work environment, will it become a widely replicated model? Considering the significant hurdles related to plant selection and cultivation, specialized glazing, and custom structural configuration—not to mention myriad other concerns including the need to employ a team of full-time horticulturalists—the Amazon project is likely to remain an exceptional, if not unique, example.

And yet, the critical insights and innovations generated by the Spheres design team provide valuable knowledge that other architects, engineers, and clients may build upon. A post-occupancy study of the Spheres would likely persuade those still-unconvinced: that a workplace infused with nature can deliver breakthroughs in employee satisfaction, productivity, and overall well-being.