Jasper and Merlin, the first two towers of Amazon’s new headquarters in Arlington, VA, have just become the world’s largest new build to achieve LEED® Platinum certification (v4 Building Design + Construction). Furthermore, they are part of Amazon’s ambitious plan to be carbon-neutral by 2040. As if that’s not enough, the buildings were designed to settle gracefully into a historically residential neighbourhood, having a positive impact on human life and wildlife in the surrounding streets. A pivotal aspect of the project lies in its conscientious use of glass, which contributes to the building’s energy performance and biophilic design. This article takes a deep dive into the strategies that ZGF Architects employed to tackle the project’s environmental goals, and how the buildings’ glass contributed to a truly sustainable building envelope.
Thanks to ZGF Principal Brian Earle, Associate Principal Rebecca Pantschyschak, and Principal Kian Shamloo for their insights into this project.
Amazon HQ2 by the Numbers
- 2 towers
- 22 stories / 327 feet tall
- Approximately 100,000 square feet of AviProtek® E bird friendly glass
- 2.1 million square feet of space
- 24% less power consumption than buildings of similar size, partly due to energy-efficient glass
- Renovation and expansion of 2.5 acres of adjacent public park, known as Met Park
Photo credit: Magda Biernat Photography
Courtesy of ZGF Architects
Carbon Reduction
The new headquarters are a showpiece project for Amazon’s Climate Pledge, which guides signatories toward net-zero carbon emissions by 2040. When it comes to building projects like this one, this means reducing embodied carbon as well as operational carbon emissions. Let’s look at the tactics involved in reducing emissions from these two key sources.
Reducing Embodied Carbon
According to the American Institute of Architects’ Embodied Carbon Guide, embodied carbon accounts for about 38% of the carbon emissions of an average office building during its first ten years. In a high-performance structure like Amazon HQ2, that number is considerably higher. Therefore, managing the carbon used in a project’s structure and building envelope has significant implications for its environmental impact during its first decade. Getting this right goes a long way toward being carbon neutral by 2040.
To reduce the building’s embodied carbon footprint, ZGF started by gathering EPDs (Environmental Product Declarations) for as many of the project’s components as they could. As Brian Earle explains, “The first step in being able to reduce carbon is to track it. And the first step to tracking is to encourage the creation of EPDs.” The declarations paid off during the LEED® application stage, helping the project earn credits under Materials and Resources – Building product disclosure and optimization – environmental product declarations, and Building product disclosure and optimization – material ingredients.
At the time of this project’s material selection, ZGF focused on reducing embodied carbon from structural components like steel and concrete. One reason for this choice was that structural materials, especially concrete, contributed relatively high levels to the project’s overall carbon footprint. Another factor was the scarcity of EPDs for building envelope components like glass and gypsum at the time. This made it difficult to track embodied carbon from those materials. Over the last several years EPDs for envelope materials have become more available, and architects like ZGF are increasingly incorporating them into project requirements.
Walker offers EPDs for Walker Textures® and AviProtek® bird friendly glass, as well as etched and unetched mirror. You can find the Environmental Data Sheets on our Sustainable Materials resource page, or contact Walker’s Customer Service Department to request the full declarations.
Photo credit: Magda Biernat Photography
Courtesy of ZGF Architects
Reducing Operational Carbon
Once the last concrete is poured and the final pane of glass is installed, sustainable architecture becomes a question of day-to-day performance. At the Amazon HQ2 towers, this includes consuming about 24% less energy than similar-sized buildings. How? The team at ZGF took a whole-building view of all the project’s components, both in isolation and in conjunction with one another, to coax the best possible performance from the towers.
For instance, the buildings’ glassy exteriors aren’t just an aesthetic choice; they make the structures more energy efficient. Brian Earle notes that, “One of the interesting things when you build a building this big is that the loads inside the building become much more important than the envelope performance (thermal control) of the building. We found that it was more important for us to reduce our energy use for lighting than to have a higher performing thermal envelope. The thermal performance and transparency of the glass really helped us optimize energy use in that sense.”
In other words, due to the high volume-to-surface-area ratio of these towers, increasing daylighting was more beneficial to overall energy performance than reducing glazed areas for the sake of thermal control. This wasn’t an obvious conclusion; it required in-depth energy modelling. However, as Rebecca Pantschyschak explained, “ZGF loves doing this kind of calculation to make sure we’re finding the right solution for the environment.”
Of course, using high-performance glass helped with this solution. The glazing for these towers is Starphire Ultra-Clear® from Vitro Architectural glass with a Solarban® low-e coating on surface two. The low-iron substrate maximizes natural light flow into the building while the low-e coating reduces unwanted heat gain. This helps to reduce the building’s overall energy consumption and shifts the design toward a fully glazed building envelope. It also brought the project one step closer to LEED® Platinum status by contributing toward the Optimize energy performance credit.
Making this project energy efficient required a whole-building perspective. By considering the glazing in conjunction with the structure’s overall proportions and energy demands, ZGF was able to reduce energy consumption and design a truly sustainable building envelope.
“The way you achieve truly high-performance is by targeting inflection points between competing sustainability objectives. The glass on this project was a critical inflection point, balancing natural daylight with solar heat gain.”
– Brian Earle, Principal, ZGF Architects
Biophilic Design
The biophilic design process for Amazon HQ2 focused on protecting local wildlife, especially birds. Essentially, ZGF wanted the structures to “land lightly” in their setting, offering the greatest benefits with the least possible disruption.
Why use bird friendly glass?
Some projects use bird safe glass to comply with local legislations or to help achieve a green building certification like LEED®, while others are bird friendly purely because the client or architectural firm is committed to protecting local ecosystems. The Amazon HQ2 project is a little bit of both.
Arlington had no bird friendly building guidelines in place when this project was approved in 2019. However, the city does offer a Green Building Incentive Policy (GBIP). Under the policy, “bonus density is offered in exchange for new developments that commit to specific sustainability criteria.” This means that large, high-density projects like Amazon HQ2 can be built in lower-density zones, provided they meet the GBIP’s sustainability criteria. The latest version of the GBIP introduces the use of bird friendly glass among its considerations. This version came into effect in 2022, just in time for Amazon HQ2 to be one of the first builds in Arlington to accept bird-friendly building as a site-plan condition.
Photo credit: Ken Wyner Photography
Fundamentally, though, the Green Building Incentive didn’t really alter the project’s direction. The team already knew they’d be designing a sustainable building envelope, including eco-friendly elements like bird deterrence. When asked if this was standard at ZGF, Rebecca Pantschyschak confirmed, “I don’t know that we have any ZGF project now that doesn’t talk about using bird-friendly glass.” At this point, bird friendly building seems to be an integral part of how the firm approaches their work.
From a LEED® standpoint, the use of bird friendly glass could have helped the project earn a credit for Innovation – Bird collision deterrence. However, ZGF had already maxed out on other Innovation credits for this project, so the bird friendly glazing wasn’t needed for their LEED® points.
Designing Hand in Hand with Audubon
ZGF consulted with the Audubon Society of Northern Virginia to plan the building’s bird safe building strategies. Taking the Society’s recommendations into account, the final design incorporates AviProtek® E bird friendly markers on the first surface and a Solarban® low-e coating on the second surface, from ground level up to 50 feet from grade.
One of the advantages of this particular bird friendly solution is that it uses the same Starphire® substrate and low-e coating as the rest of the project, so the glass matches perfectly and creates a cohesive building envelope. Another perk is that it offers both bird deterrence and solar performance in a single glass product, helping ZGF achieve multiple sustainability goals with a single material.
Insulated glass unit: 6mm Starphire Ultra-Clear® glass with AviProtek® E bird friendly markers on surface 1 and Solarban® low-e coating on surface 2
Photo credit: Ken Wyner Photography
Kian Shamloo explained that he recommended this glass based on extensive research into bird deterrent solutions, coupled with past experience with Walker Glass products. “Comparing all the technology that was available at the time,” he explained, “I still gravitated to the most basic system, which was also, in my opinion, the most effective.” That meant a first-surface etched pattern covering the surface of the glass. The first-surface placement ensures that markers will be visible in all conditions, and the all-over coverage doesn’t leave tantalizing “gaps” for birds to attempt to fly through.
We should note that only the walls facing the nearby Met Park incorporate bird friendly glass, whereas windows facing away from the park use regular unetched glass. The design team felt that birds would be most at risk when taking off from the parkland habitat, so they focused the project’s bird friendly resources in that direction. It’s an unusual approach but it has precedents in legislations such as San Francisco’s Standards for Bird-Safe Buildings.
As we’ve seen, the sheer scale of the Amazon HQ2 towers has a major impact on their design. Their size determined which energy strategies would be most efficient and what material choices would have the most impact, as well as making the project a candidate for Arlington’s Green Building Incentive Policy. The scale of the project also means that it is guaranteed to influence the surrounding environment, whether for better or for worse. The team at ZGF was acutely aware of this. During the design phase, they took pains to ensure an overall positive impact through extensive modelling and consultation with local experts like the Northern Virginia Audubon Society, among other tactics.
On the other hand, they also paid attention to the complex ways that small decisions interact with each other through the structures. They studied the relationships between each set of components, as well as analyzing material choices in isolation. Add up all these inflection points, and the result is a landmark site that will benefit its occupants and surrounding neighbourhood in almost immeasurable ways.
