2013 ASHRAE TEcHnology AwARd cASE STudiES they are extremely happy with the thermal comfort provided by the radiant slabs. Innovation The design process invested in early energy modeling and analysis. A full energy audit was conducted of a neighboring fire station to determine standard practice and how energy use could be reduced in all areas. Economic decisions about energy efficiency measures were made with a long-term net zero energy perspective in mind. This focus on individual energy uses and the close involvement of the building occupants throughout the design process made this building project extremely successful. The design team developed an innovative approach to small-system, variable speed pumping. The system includes three identical nominal 5-ton (17.5 kW) waterto-water heat pumps; one for domestic hot water, one for heating, and one for cooling. A single 5-ton (17.5 kW) heat pump can meet the heating or cooling load under a majority of conditions; however, the heating and cooling heat pumps are valved so that during peak An 8,000 gallon cistern provides water for toilet flushing, laundry, irrigation, and truck washing. A 30 kW solar array reduces the station’s EUI to 22.3. events when one heat pump cannot keep up, the cooling heat pump can switch over to back up heating and vice versa. This provides safety and redundancy while keeping the mechanical equipment as small and simple as possible. Each heat pump requires 15 gpm (0.95 L) of water flow. The control system monitors how many heat pumps are operating and sets the variable www.info.hotims.com/44636-42 62 ASHRAE JouRnAl ashrae.org Septem ber 2013