United Therapeutics Unisphere



United Therapeutics believes the reduction of the carbon footprint of the community benefits us all.

This project is a net-zero energy building creating 120,000 SF of new office space, 10,000 SF of retail space, a 75,000 SF parking garage, as well as public amenity space for the Silver Spring community. United Therapeutics decided early on that this project would pursue net-zero, meaning it will not use any more energy than it could produce through renewable means on site over the course of a year.


The Energy


The building communicates its energy usage patterns in real time through several occupant feedback systems. The Energy Wheel, a large sundial-like sculpture made purely out of LED lights and reflective metal fins, is the centerpiece of the building’s feedback system. It is installed on the building’s atrium wall and is visible from all office floors. The Energy Wheel is driven by real-time data from the building’s control systems. It translates this data into giant, 40-foot rays of light that animate in sequence, moving inward and outward to demonstrate the building’s energy usage/consumption as part of the ebb and flow of net-zero operation.

The wheel pulses light outward when the building’s systems are generating a surplus of energy and inward when the building is using more energy than is currently being produced. This also serves as a visual cue to the building occupants to adjust their behaviors with respect to energy use. There is also a suite of custom light animations that relate to critical thematic moments throughout the day, such as Solar Noon, which relates to the sun’s peak position in the sky. These kinds of large-scale visual changes create a central viewing platform for employees and visitors to rally around their net-zero efforts.



The centralized building automation system is key in reducing building energy use. It optimizes system performance, sets occupied/unoccupied modes and sets back temperatures and ventilation in areas where possible through occupancy sensing. In addition, interfacing lighting controls, power monitoring and other building systems into the centralized control system further improve performance. The project incorporates energy meters on the building’s various systems to provide valuable feedback for benchmarking and trending. With this information, building operation can be modified in real time and the energy effects can be observed.

Thermal Pool

A central feature of the atrium is the swimming pool and its automated structural cover. The pool cover raises when the pool is not in use to create a walkable surface that is both super-insulated and vapor tight to greatly reduce heat and water loss when the pool is not in operation. The pool is heated through a water-to-water heat pump that efficiently utilizes excess heat load from the building and aids in balancing the annual heat profile of the facility.


The Unisphere project includes nearly 3,000 high-efficiency solar panels to generate enough power over the course of a year to offset the building’s entire annual energy consumption. The photovoltaic system is designed to produce over 1,175 MWh of green power per year.



Increased insulation, triple-paned glazing and electrochromic tinting glass, which tints in response to the sun, have resulted in significant thermal improvement over minimum code values. Electrochromic glass automatically changes tint based on a variety of factors, including season, location of sun, cloud coverage, glare from adjacent structures and tenant preference. The intelligent tinting helps reduce the amount of thermal energy entering the building and delivers a more comfortable work environment, enhancing occupant well-being.

Natural Ventilation

The building is designed to provide natural ventilation during times of the year when outdoor air conditions permit. Under these conditions, windows located beneath the raised floor automatically open to provide a crossflow of air. In this mode, the occupant can choose to open additional glazing above the floor to increase the ventilation rate to their space. The building atrium acts as a thermal chimney, utilizing the buoyancy of warm air to induce airflows through the building. As outdoor air temperatures increase, variable speed fans located at the top of the atrium provide a “ventilation assist” to induce flow.

Daylight Harvesting

Integration of a daylighting strategy into the building design reduces energy use while improving occupant comfort. The key for an effective daylighting strategy is to optimize the building orientation, glazing selection and integration of the daylighting control and HVAC systems. A building energy and daylight model was completed to optimize the daylighting strategy. High ceilings paired with high light transmittance glazing, increases the amount of daylight available in the space and increase daylight penetration into the core. Photovoltaic sensors throughout the space automatically adjust lighting levels depending on the amount of daylight available. One hundred percent of regularly occupied spaces in Unisphere have access to daylight.



High Performance Buildings National Leader
Greg Botteon
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Sustainability National Leader
Kim Ilardi
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