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地址: Bethesda, MD

建筑面积: 27,400 sq. meters

竣工日期: April 2001

高度: 7-story building

能源利用: To minimize energy consumption at the Louis Stokes Laboratories, designers focused on the equipment that supplies, conditions, and moves the large amount of ventilation air required to maintain a safe environment. Rather than maintaining a constant supply air volume, the variable-frequency drives (VFDs) on the building's fan systems reduce the volume of air delivered to the space when the building is unoccupied, from a maximum volume of 400,000 cubic feet per minute (cfm), or 15 air changes per hour, to 160,000 cfm, or 6 air changes per hour. The variable-speed drives lower the speed of the supply and exhaust fans to accomplish this reduction and move less air.

The VFDs on the pump system operate in much the same way as they do on the VAV supply and exhaust fans. Differential pressure sensors in the water-distribution piping system signal the VFDs to reduce the pump flows in response to a corresponding reduction in the cooling or heating coil control valves.

This is the first NIH building to install VAV fume hoods. Although they are more expensive and complex to design, install, and commission, they have the highest degree of face velocity control. (Face velocity is a measure of air flow at the front, or face, of a fume hood; it indicates the effectiveness of hood containment.) Energy savings can be as high as 70% in comparison to energy use associated with CV hoods, but users must be trained in operating the hoods to realize these savings.

The most important and largest application of energy recovery in the research facilities is in the laboratory exhaust systems. NIH selected desiccant energy recovery "heat wheels" as the method of heat recovery for general building exhaust. The heat wheels use heat-absorbing desiccant disks that rotate sequentially, transferring energy from the building's general exhaust to the supply air streams. The wheels used in this project recover both sensible and latent energy and have rates of efficiency between 60% and 70%. The supply and exhaust air streams must be adjacent to each other to allow the wheel to rotate through both alternately; this requires that the mechanical penthouse be high enough to accommodate higher air handling units (AHUs).

A common concern about heat wheels is the potential for cross contamination between the air streams. Although the wheels have a self-purging system that has been proven to limit cross contamination to 0.045%, NIH did not exhaust the containment devices (fume hoods, biological safety cabinets, etc.) through the wheels, but created a separate exhaust system. As a result, a smaller volume of air (roughly 20%) passes through the heat recovery wheels, lowering energy savings.

Direct digital controls with pneumatic actuators are used for the mechanical HVAC building systems. A building automation system provides a central computer station in the maintenance office with graphic displays of AHUs, exhaust fans, fume hoods, VAV terminal units, room temperatures, room differential pressures, pumps, heat exchangers, and central utility consumption.

The programmable lighting control system for the building contributes significantly to total energy savings. It allows the lighting for the entire building to be automatically shut off at a predetermined time, but manually overridden by users who are working late.

From an architectural standpoint, the key energy-saving feature in the building is the method of capturing daylight by ending the modified interstitial floors 12 feet back from the window walls of the building and using a curved ceiling above the resulting double-height spaces to take advantage of the double-height exterior windows. Daylighting is sufficient to light lab benches 30 feet in from the window walls, and lighting above the lab bench space consists of T-8 fluorescent lamps and electronic ballasts on photo-sensor controls. The building also uses light-emitting diode (LED) exit signs and motion sensors in break rooms, conference rooms, and bathrooms.

室内环境品质: The interstitial mechanical floor that is located above each occupied floor ends 12 feet back from the window walls of the building, leaving a double-height space around the building's perimeter where the personal workstations are located. A curved ceiling above this space takes advantage of the full floor-to-floor wall height of 18 feet and the double-height windows, which admit enough daylight to light lab bench areas 30 feet in from the window walls.