REI opens a net zero energy building, and shares its design process on constructing a building that produces as much energy as it uses
Outdoor gear retailer REI has been building its retail stores and distribution centers to LEED-standards for two decades. But when the consumer cooperative was ready to open a third distribution center in the Southwest, it decided to take on an additional challenge: constructing a net zero energy building (NZEB) that would earn LEED platinum certification.
It was a logical next step for a company that emphasizes both environmental and fiscal responsibility in its operations. “We want to be connecting people to the outdoors for generations to come, and with that perspective, we choose to take a long-term view on investments, especially the large capital investments we will be operating on behalf of our members for decades to come,” said Kirk Myers, senior manager of sustainability.
REI’s net zero energy distribution center, which opened in 2016, includes a 2.2-megawatt solar energy system that annually produces as much power as it consumes. It should pay for itself in about five years. Other energy-efficient features include LED lights that turn off when not in use. The design team also chose both the building orientation and the location of various activities inside the facility with an eye to minimize energy usage. The loading dock, for example, is positioned to limit heat coming in from outside.
Reducing design uncertainty
The initial step in the construction of REI’s net zero energy building was modeling the project’s feasibility from an engineering and economic perspective. Then, after choosing design and construction partners, REI held a three-day design charrette facilitated by the Rocky Mountain Institute, an organization focused on promoting sustainability and energy and resource efficiency. Myers said having this process in place was the most critical factor in achieving REI’s desired outcomes.
In most building projects, engineers will design systems that deliver more performance than the building will actually need, because they don’t have a good understanding of how other building elements might impact their system’s performance. “No one wants to be the failure point,” Myers said.
The REI design charrette, however, gave engineers and designers insight into how systems would work together as a whole, reducing their uncertainty about each individual system’s required performance.
“An energy modeling firm did a robust energy model that allowed us to understand exactly what the optimal amount of insulation would be in different walls of the building – east-facing versus west, north or south-facing,” Myers said. Through the discussions, HVAC engineers gained a good understanding of the envelope construction and its performance of other processes that could emit heat, and impact cooling requirements. Armed with that knowledge, they didn’t have to over-design the system to ensure it would perform effectively. “It allowed the uncertainty to be reduced significantly, which allowed us to use smaller HVAC tonnage,” Myers said.
However, this was not a simple process. “Since we were aiming for net zero energy, the energy model had to be very, very sophisticated. We had to understand how the production rate, the volume that is moving through the warehouse, works at different times of the day and also seasonally, with our big anniversary sale in May and of course the holidays. And how do those production periods line up with how hot it is in Phoenix at that time?” Myers said.
The integrated design process answered such questions, trading an investment of time up front for savings on first cost and on total costs of ownership, he added.
Choosing technology
Before the design charrette, REI had identified a number of technology innovations that might be used in its new distribution center. Part of the work of the design charrette was to determine whether or not such technologies would be viable. “In the end, what we put in the building was relatively established technologies; we just thought through how to integrate them into the building in a very considered way,” Myers said.
The design charrette participants also examined various alternatives for several building systems. They discussed and ultimately decided against precooling air going into the AC system by running it underground. They looked at installing a direct current microgrid, which could take the DC current from the solar panels and use it to directly power electric forklifts and similar loads that use DC. That would eliminate the energy loss that comes with converting power from DC to AC and then back to DC. “But back in 2015 that was just a little too cutting edge. We couldn’t get UL-listed fixtures, so we decided against it,” Myers explained.
Charrette discussions also guided the placement of the building’s skylights. REI and its partners designed and installed a robotic fulfillment system in the distribution center; it enables one person to process items eight times faster than they normally could. Since the robots don’t need light to operate, and, REI employees spend little time in the robotic area, the designers were able to cluster the skylights over areas of the building where humans would be working. This left plenty of roof room to install the large solar array.
At times the charrette participants determined that the most energy efficient solution for the building wasn’t the best choice. “We installed the highest efficiency HVAC system we could get, but it’s still using more electricity than we would have if we had gone with an evaporative cooling system,” Myers said. “But, we saved millions of gallons of water a year in a desert environment by making this choice. That was part of our approach, obviously thinking about energy but also thinking about the total impact this building would have on the local ecosystem.”
Despite water-saving features like no-flush urinals and other high-efficiency fixtures, REI could not reach its goal of zero additional water usage for the facility. So it funded a project that made irrigation improvements for ranchers in the headwater areas of the Verde River. “We are now ensuring that there is, by a huge factor, more water going into that river and into that watershed than we are taking out for consumption by our building,” Myers said.
Offering best practices information
During this multi-year design and construction process, REI learned a great deal about net zero energy building. Now it is making that information available to other companies considering similar projects.
“That’s part of our theory of change,” Myers said. “REI is here to help protect the outdoors for generations to come, so we want to share that information broadly. Part of our collaboration with the Rocky Mountain Institute and the U.S. Department of Energy is to put together a showcase portfolio on this building and to share the best practices – the things that we were successful at, the things that we weren’t able to do. We want other folks to take that and learn.”
Myers said distribution center projects are typically more focused on fast execution than on sustainability. To change that, more companies should integrate a charrette-type conversation into their design process. “Companies today are recognizing that there is a lot of opportunity to reduce operating costs by taking this sustainable approach,” Myers said. The upfront time required for this process can be offset by both financial and environmental benefits over the long term.
“REI is here to help protect the outdoors for generations to come, so we want to share that information broadly.”
Kirk Myers, REI
REI Distribution Center – the numbers behind zero energy
• The facility’s 2.2 megawatt solar system produces renewable energy on-site, enough to power the entire facility annually. The system is expected to provide REI with 20 years of free energy and pay for itself in five years.
• REI and its partners have designed the industry’s first omni-channel one-touch fulfillment system, enabling one person to process items eight times faster than the typical distribution center, meaning outdoor enthusiasts will get their gear faster.
• Despite being in the middle of a desert, the distribution center will help restore the nearby Verde River by enhancing water flows and recreation access.
• The distribution center features a non-evaporative cooling system to keep employees cool in the desert heat. The system is fully powered by renewable energy and saves millions of gallons of water every year.
By: Mary Lou Jay
