United Therapeutics Corporation is an American publicly-traded biotechnology company that specializes in developing innovative therapies for rare diseases. In 2019, the company completed the construction of a new 135,000-square-foot headquarters in Silver Spring, Maryland. The Unisphere is a testament to the company's commitment to sustainability, using a variety of energy generation, efficiency, and embodied carbon innovations to reach net zero status.
Designed by EwingCole, the Unisphere was regarded as the largest net zero building in the world when it was completed four years ago. According to United Therapeutics, the primary use of the building is “managing the development of an unlimited supply of transplantable organs”, which will be achieved through a mix of office and laboratory space, as well as a highly controlled storage and distribution facility.
In this research note, we explore the various factors that have helped United Therapeutics develop net zero buildings and the barriers they have had to overcome during their four years in operation.
The building originally featured a 320 kW rooftop solar array that covered approximately 25% of the building's roof area. Its parking lot was covered with solar canopies that provide shade for parked cars while generating up to 256 kW of electricity. And, the Unisphere also featured two 80 kW on-site wind turbines that generate electricity that is used specifically to power the building's lighting and HVAC systems. Subsequent expansions and upgrades have taken the total energy generated on-site to over 1MW, equivalent to 10% of the building’s total 2021 electric consumption.
Off-site, United Therapeutics procures renewable energy from wind and solar farms located throughout the region. The company purchases renewable energy credits (RECs) that are equivalent to the amount of electricity that the building consumes. The RECs ensure that the electricity consumed by Unisphere is offset by the production of renewable energy elsewhere in the region. In 2021, The Unisphere purchased RECs that equal 90% of the total electric consumption, underlining the challenges of on-site generation and net zero buildings.
The building also features an on-site geothermal heating and cooling system, where 52 geothermal wells drilled more than 500 feet into the earth use its relatively constant temperature to heat and cool the building over the course of the year. During Maryland’s cold winter months, a heat pump extracts heat from the ground and uses it to warm the building. And, during the state’s hot summer months, the process is reversed, and the system extracts heat from the building and stores it in the ground.
In conjunction with the geothermal well system, a thermal pool also helps generate energy to reduce the electricity load on the HVAC system. Located in the building atrium, the thermal pool serves as a source of evaporative cooling and heat rejection.
In addition to generating clean energy on-site and procuring renewable energy off-site, Unisphere is designed to be highly energy efficient, incorporating a number of features that help to reduce energy consumption.
One of the most striking features of the Unisphere is the building’s high-performance electrochromic envelope, offering increased insulation, triple pane glazing, and electrochromic tinting glass, which tints more or less depending on the location of the sun. The building achieves a 25% thermal improvement over minimum code values, simply by reducing the amount of thermal energy entering the building.
The building's efficient HVAC system uses a combination of displacement ventilation and underfloor air distribution to provide conditioned air to the building's occupants. When outdoor air conditions permit, the building is designed to use natural ventilation. Windows below the floor at the building perimeter and above the ceiling at the building interior opens to provide a cross flow of air, while the atrium acts as a thermal chimney, utilizing the buoyancy of warm air to induce airflows.
Intake air into the atrium is routed through an underground concrete labyrinth beneath the parking garage to pre-heat or pre-cool the air by placing the airstream in contact with the relatively constant temperature of the earth. The atrium does not maintain the same interior temperatures as the fully conditioned areas of the building, but acts as an “air blanket” between the core building and the outside world.
The Platinum LEED-certified building's efficient lighting system is controlled by occupancy sensors, which ensure that lights are only on when a room is occupied. The lighting system also incorporates daylight sensors, which adjust the level of artificial light based on the amount of natural light in a room. High ceilings paired with high light transmittance glazing located near the ceiling increases the amount of daylight penetration into the core, while sensors throughout the space automatically adjust lighting levels depending on the amount of daylight available.
The building has initiated plug load management policies that require the purchase of EnergyStar rated equipment and force computers into hibernation mode during unoccupied periods have also reduced overall energy use. The installation of timers or controllable circuits that de-energize power to devices such as vending machines, coffee makers, routers, printers and other types of office equipment have reduced these wasteful “vampire loads”.
Built on the Schneider Electric EcoStruxure platform the building continually manages energy use by optimizing system performance, through lighting controls, power monitoring and other building systems into the centralized control system. And, incorporation of energy meters on the building's various systems have provided actionable intelligence for benchmarking and implementation strategy.
Acting ahead of the curve in 2017-18, the building was designed with embodied carbon in mind, featuring a number of sustainable materials that help to minimize the environmental impact over the full life-cycle of the project.
The building's exterior walls were constructed using insulated precast concrete panels, which were manufactured off-site to help to reduce the amount of waste generated during construction. The building's flooring is made from recycled content, and the building's structural steel was sourced from a local supplier. While a number of other sustainable materials, including low-emitting paints and adhesives, as well as low-flow plumbing fixtures were applied.
The company's founder and CEO, Martine Rothblatt, has been a vocal advocate for clean energy and sustainability. Rothblatt's commitment to sustainability has been a driving force behind the company's efforts to create net-zero buildings. About Rothblatt, Thomas Kaufman, the company’s director of corporate real estate, said; "she felt very strongly that you cannot achieve net-zero as an afterthought. It has to be a mandate at the beginning that drives every single decision.”
Net Zero Buildings Environment
Maryland has been a leader in environmental regulation on buildings, setting standards that are generally more stringent than the national average. The state has adopted the International Energy Conservation Code (IECC) as its building energy code, and implemented the Maryland Green Building Council, which provides guidance and support for sustainable building practices.
The state has set ambitious renewable energy and energy efficiency targets, including a goal for all new buildings to be net zero energy by 2030, which has led to a more supportive policy environment for the creation of net zero buildings. Maryland has even incentivized and openly promoted the use of renewable energy sources, such as solar panels and geothermal systems, in new commercial construction.
The success of the project has now inspired the company to expand their net zero portfolio with the acquisition and redevelopment of two buildings adjacent to The Unisphere.
The neighboring Hampton Inn and Homewood Suites Hilton hotels closed abruptly in October 2021 and the two properties were purchased by United Therapeutics. The company will reportedly redevelop the two buildings significantly, then absorb the embodied carbon cost with mass timber construction, expanded solar panel arrays, and advanced building automation. Officially called the Unisphere Annex, the two new buildings will presumably be connected to the current headquarters, which could restore its crown as the largest net zero building in the world.
“Every element [of the Unisphere], from the overall building form to the interaction between building systems, was designed to optimize energy saving strategies. This interactive, intelligent building communicates its operations and inspires others to strive for high performance,” a company statement said. “Going forward, we will strive to ensure all new buildings are ‘site net zero’ to the greatest extent practicable — accomplished through a variety of technologies, including solar power, geothermal exchange, earth-coupled heating and cooling, and intelligent building automation systems.”