54-Year-Old School Becomes a Green Lab

Challenge:

Designed for ninth grade students, T.C. Williams High School’s Minnie Howard Middle School is located in Alexandria, Va. The 54-year-old school is dedicated to Minnie Howard, Alexandria’s first PTA president. Since 1993 the school has provided Alexandria’s ninth grade students with a successful transition from middle school to senior high school.

In 2008, Alexandria City Public Schools (ACPS) hired the Leesburg, Va., offices of Hayes Large Architects LLP and B2E Consulting Engineers to help turn the Minnie Howard campus into a laboratory for testing green building technologies that could be implemented system-wide.

Hayes Large and B2E devised an innovative package of technologies to form one of the most energy-efficient systems in the country. These included a creative combination of solar and ground-source geothermal energy to significantly lower heating and cooling costs, a water-source Variable Refrigerant Flow (VRF) zoning HVAC system to simultaneously cool and heat the building, water source heat pumps, solar heat exchangers, low-flow plumbing fixtures, and tubular skylights to bring sunlight to classrooms, corridors and bathrooms.

Solution:

Synchronizing all of these sophisticated technologies into one unique system was a challenge. However, B2E turned to Mitsubishi Electric Cooling and Heating Solutions, Suwanee, Ga. because they understood that Mitsubishi Electric’s new water-source W-Series units would physically fit into the tight spaces in the mechanical room and the Mitsubishi Electric VRF zoning technology would perfectly support B2E’s aggressive profile for efficiency and sustainability.

A collection of 42 solar collector panels were placed on the front of the school to provide active solar water heating and serve as a sun shade, reducing glare and cooling costs. For the new geothermal system, a field of 60 wells was drilled 300 feet beneath the school parking lot.

Well drilling began in April 2009. General Contractor Caldwell and Santmyer, Inc., Berryville, Va., first removed the 50-year-old HVAC system that included two locomotive-sized boilers and chillers. They brought in Shapiro & Duncan, Inc., Rockville, Md., to install the six Mitsubishi Electric water-source VRF zoning units located next to the back-up boilers, solar heat exchanger and the makeup outside air unit. Shapiro & Duncan also set up the complex plumbing network that connected the 8,000 feet of piping which joined the geothermal closed loop water system to the six WR2-Series INVERTER-driven units.

“Of all my years in HVAC contracting, this Minnie Howard system stands in a league of its own,” said Chris Ott, project manager, Shapiro & Duncan. “It’s an ingenious bit of green engineering. The school went from an antiquated chiller that was keeping water at 40 degrees and two huge, inefficient boilers maintaining 180-degree water all the time – even if it wasn’t needed – to a variable speed condensing unit coupled to a geothermal well system that only runs if an indoor air handler needs cooling or heating. Add to this the ability to cool and heat simultaneously and to zone with multiple condensing units – another energy-saving milestone.”

Ott was impressed with the W-Series system from Mitsubishi Electric – utilizing water as a heat exchange medium – used in conjunction with the geothermal wells. “It was a very logical solution for energy conservation.” Ott said. “I also like the reduced cost of labor and materials needed for installation because Mitsubishi Electric is the only two pipe system in the industry. The installation was hassle free and the system started up the very first time with no glitches. When you consider there are 8,000 feet of piping, that’s amazing!”