Philip Merrill Chesapeake Bay Foundation Floor Plan

Since moving into the Merrill Center in 2000, CBF has done extensive work with the National Renewable Energy Laboratory (NREL) of the Department of Energy National Laboratory. NREL monitored the building's energy and water performance from November 2001 to November 2002. Annual energy usage was measured to be 39.9 kBtu/square foot/ year, inclusive of plug loads and miscellaneous loads like exterior lighting and elevators. This is 59.0 percent less than typical office buildings based on 1995 data collected by the Energy Information Administration. Through NREL's analysis, CBF learned their plug loads were higher than what had been anticipated, so they went back to verify that all possible plug-ins, including soda machines, were on motion sensors, and that all office equipment purchased was Energy Star-rated. The center clearly leads by example, and the research done postoperation will be helpful for planning future high-performing commercial building designs.

NREL's monitoring also looked at the building's water consumption. Total water usage for one year was 39,937 gallons, of which 33,372 gallons (83.5 percent) was provided by way of rainwater harvest-

Reduction Motion Compost
TOP: Wind diagram. BOTTOM: Building section.

ing and reuse. The balance of water usage, 6,565 gallons (16.5 percent), was supplied by the on-site well. Total water usage at CBF averaged 1.25 gallons/square foot/year. According to BOCA Plumbing Code, a conventional office building uses 12.66 gallons/square foot/year. Thus, CBF uses approximately 10 percent of the water of a conventional office building. Such a significant reduction is attributed to composting toilets and rainwater harvesting and reuse at lavatories, clothes washer, and mop sinks. CBF reports that the composting toilets work better than expected. While CBF staff doesn't think twice about them, composting toilets are a real interest for visitors. Maintenance is minimal and compost is applied to grounds around the facility. For a 30-acre site that has been restored to native ecosystems, CBF could use all of the compost it can get.

While conserving water and energy, the Merrill Center would also have to be an effective and inspiring workplace for the 90-plus staff who work everyday inside. A study conducted by the Center for the Built Environment at the University of California, Berkeley, surveyed 25,000 occupants of 150 buildings to question users' satisfaction regarding air quality, comfort, acoustics, and lighting. Of the 150 buildings rated, the Philip Merrill Environmental Center received the second highest overall satisfaction score. Mary Tod Winchester, CBF's vice president of administration, states, "The facility is a major recruitment tool. We have a much higher level ofjob applicants and more applicants per job than before we moved here."

Chesapeake Bay Foundation, Philip Merrill Environmental Center 69

A goal for the design of the Merrill Center was to provide passive cooling through natural ventilation for a portion of the year. While this is feasible in smaller projects or in more moderate climates, naturally ventilating an office building in the hot, humid mid-Atlantic climate can be a challenge. By gathering climate data from Thomas Point lighthouse, located just off the shore from the Merrill Center, the SmithGroup estimated that the climate could support natural ventilation for approximately 9 percent of the year—when outdoor conditions were between 68° and 77°F (20° and 25°C) and 20 to 70 percent relative humidity.

The building was oriented to take advantage of cool spring and fall breezes coming off of the bay. Awning windows in the south facade were located low to catch breezes from the bay. High awning windows along the north elevation and in each of the dormers were located to maximize stack and cross ventilation. Window locations and sizes were dictated by research into the wind effects and flow patterns throughout the building. Running continuously along the inside of the south facade, a 5-foot-wide slot between the first and second floors was added to increase air circulation throughout the space.

The outside temperature and humidity is constantly monitored by the building's energy management system, and when it is determined that outdoor conditions are suitable for natural ventilation, the dormer windows will open automatically, a green light will turn on throughout the building signaling users to open the operable windows, and the mechanical system will shut down. Operable windows are ganged together to minimize the effort of opening the many windows that span the facade. This approach might not be appropriate for every type of client, but the staff of CBF is more than willing to actively




(1 Building exposes maximum surface to breezes

(2 Awning windows promote airflow into the building at 1st amd 2nd floors

@ Inlet and outlet openings are located in opposite pressure zones

(4 Openings on all sides force airflow to change direction increasing ventilated area

© Lager outlet area than inlet area products higher velocity --- best for hot/humid climates

Natural ventilation.

engage in the operation and performance of the building. By replacing costly motorized operators, this sweat equity does dramatically reduce the cost of the mixed-mode natural ventilation system. This combina-

tion of high-tech and low-tech solutions is found throughout the Merrill Center. With very few exceptions, the Merrill Center used strategies like natural ventilation, composting toilets, geothermal cooling, and daylight-ing, which have been used successfully before in smaller buildings. What is most unique about the Merrill Center is the breadth of strategies used and the combined effect to reduce resource consumption in a larger z >

c range where the building could be cooled using natural ventilation, while maintaining the comfort of the building occupants. The systems in the building were interactive enough to accommodate this adjustment.

Roger Chang, a graduate student at the Massachusetts Institute of Technology Cambridge, studied the center as part of his master's thesis and reported his findings in "Case Studies of Naturally Ventilated Commercial Buildings in the United States" (2002). Chang found this estimate to be conservative and, through the use of data loggers, discovered that natural ventilation was used for 34 percent of weekday working hours during a much larger and cooler range of outdoor temperatures. Because the monitoring systems will only trigger natural ventilation during times when humidity levels do not exceed 70 ^^ percent, there are no impacts on materials that result from excess humidity indoors. Based on detailed thermal comfort surveys, Chang learned the center's occupants generally favored the use of natural ventilation compared with mechanical conditioning. The survey results also show that occupant thermal-comfort expectations differed between natural ventilation mode and mechanical air-conditioning, a fact that could partially explain the greater than anticipated use of natural ventilation at the center. A finding like that can expand the viability of natural ventilation in climates that were previously thought to be poor candidates for passive cooling.

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