Dewberry Innovation Case Study
Engineering an Energy-Efficient Office Tower
Dewberry MEP Engineering Results in LEED Platinum, DEES Certifications for Downtown DC Building
Green. Sustainable. Renewable. In today’s environmentally conscious world, the buzzwords of energy-efficiency are often used and well understood. But what does it take to get there? That was among the challenges facing our mechanical/electrical/plumbing (MEP) engineers at the outset of a major renovation of a 340,000-square-foot office building located in Washington, D.C.’s Central Business District.
Zoning Rules Translate into Tight Spaces
One of the earliest challenges on the project was brought about by the building’s location: zoning regulations in D.C. stipulate that no structure can be higher than the U.S. Capitol building. As a result, floor-to-floor heights in most of the city’s buildings are traditionally smaller than usual. This meant that new ductwork, registers and piping had to be designed to fit into smaller, existing spaces.
Another obstacle was keeping the building’s street-level retail stores operational while the various systems were being replaced or upgraded – no small feat considering the sheer amount of work happening both above and below the stores. Through thorough planning and close coordination with the vendors, each store experienced only two weeks of downtime over the duration of the project.
Dewberry Innovation in Action
To achieve maximum energy efficiency, our MEP engineers designed a system using low-temperature VAV air-handling units and a high-efficiency variable primary and variable condenser water chilled water system to achieve wide differential temperatures in both the building’s air and water systems. While more typical chilled water and VAV AHU systems deliver a 12-degree water differential and a 20-degree air differential, we were able to push the building’s new chiller to achieve differentials of 18 and 30 degrees, respectively. By devoting more power to the chiller, we were able to dramatically reduce the load consumed by the building’s pumps and fans, ultimately using only 30 percent of the pumping and fan power used by standard systems while delivering the same peak BTUH of heating and cooling. Using variable flow pumps and fans allowed us to design a system that matched performance to demand, achieving further efficiencies and savings.
We were also able to achieve fresh-air ventilation rates that exceed American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) requirements by 30 percent. Further, we specified advanced lighting controls to minimize light pollution and high-efficiency plumbing fixtures that will save approximately 94,000 gallons of potable water each year.
Recognition From the Highest Authorities on “Green”
As a result of our efforts and those of developer Hines, the project – 1200 19th Street, NW – was awarded LEED Platinum certification under the Core and Shell rating system by the U.S. Green Building Council. Additionally, the project has been recognized as Designed to Earn the ENERGY STAR® with a design rating of 99 out of 100 points, earning it a spot among the top two percent of buildings nationwide in terms of energy efficiency.
Our MEP engineers have worked with Hines on a number of envelope-pushing projects, including the Gannett/USA Today world headquarters in McLean, Virginia; Bridgewater Crossing in Bridgewater, N.J.; and the new 1.3-million-square-foot CityCenterDC development at the site of D.C.’s former convention center.