Ashrae Journal - November 2008 - 41

through the use of occupancy sensors in classrooms and the large multipurpose room. When these spaces are not occupied and the correspondingly large quantities of ventilation air are not required, control dampers stop the supply of the ventilation to the associated unoccupied space. The ventilation unit also uses a variable speed supply fan to minimize the amount of fan energy required to deliver the ventilation air. The occupancy sensors also automatically set back the space set-point temperatures when the associated room is unoccupied. When unoccupied, the fan-coil units only operate on a call for heating or cooling; HVAC energy is only used when it is needed. Space setpoint temperatures are set back even further when the entire building is unoccupied (nights). In addition to the occupancy sensor in the large multipurpose room, CO2 sensors were provided to better align the ventilation rate with the actual occupancy. The occupancy sensors could determine whether the space was occupied but could not determine the quantity of people. The CO2 sensors allow only a minimal amount of ventilation air into the space until actual measured CO2 levels rise and the outside air quantity is increased. To minimize mechanical heating and cooling during tepid weather conditions, natural ventilation is used. A manual override switch allows for a majority of the HVAC equipment to be turned off and windows opened for natural ventilation and corresponding energy savings. Within the administration area, a control light tied to outdoor temperature turns from red to green when outside conditions are correct for natural ventilation, alerting the staff to switch off the HVAC equipment and open the windows. For periods when not enough wind occurs for effective natural ventilation, an exhaust fan positioned high near the peak of the roof provides additional ventilation and comfort without engaging the HVAC system. Conclusion The building’s energy saving features were assessed by collecting a years’ worth of electrical meter readings. Although the number of visitors to the building had not yet reached peak levels, the building consumed only 228,320 kWh or 41,000 Btu/h ·ft2 ·yr (129 338 W/m2) (does not include the separately metered well pumps). This compares favorably to U.S. Department of Energy 2006 Buildings Energy Data Book averages for comparable building types: 117,700 Btu/h · ft2 · yr (369 087 W/m2) for public assembly; 80,600 Btu/h · ft2 · yr (254 260 W/m2) for education; and 88,000 Btu/h · ft2 · yr (277 603 W/m2) for office. The Environmental Discovery Center was designed to demonstrate Metroparks’ commitment to environmental education and good stewardship of our natural resources. The energyefficient building is used by the Metroparks as a showcase for environmental education, nature interpretation, water resource management, and sustainable design practices. www.info.hotims.com/16019-42

Ashrae Journal - November 2008

Table of Contents for the Digital Edition of Ashrae Journal - November 2008