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Fuel Source: Going to heat-pump based heating systems


Creating a new early learning center presented a building size and space conditioning need of unique scale for the district. This smaller scale facility would require space cooling throughout, operate efficiently year over year, and require minimal maintenance. The system would also need to provide thermal comfort to a demographically diverse occupant – from age 4 to 25+ years old. Working closely with district staff a new all-electric HVAC system was introduced to their operating inventory: dedicated outside air system (DOAS) coupled with heat recovery variable refrigerant flow system (VRF).

Centralized DOAS air handlers with heat recovery minimize energy required to pre-treat ventilation air and paired with zone level variable volume terminal units allow tight control of ventilation air volumes for all zones. Each DOAS unit also has dedicated air source heat pump VRF condensing units to provide efficient tempering of ventilation air. Interior spaces have zone level fan coils that can move heating/cooling loads capturing heat before relying on outdoor VRF condensing units. Efficient mechanical systems coupled with a well-insulated envelope and efficient lighting allowed for air-to-air heat pumps providing 26 Btu/SF.

Owner: Shoreline School District
Scale: 54,000 sf
Completion: 2018
Energy Utilization Index (EUI): 23.9
Hours of Operation: 7:00 a.m. – 6:00 p.m.


Cedar Falls headquarters is a mission-critical facility in a location susceptible to extended power outages and seismic activity adjacent to Chester Morse Lake watershed. Hosts to functions that administer and protect the critical public infrastructure, the replacement facility was designed to operate independently of carbon emitting fuel sources and the power grid during power outages. The mechanical systems were designed to support an all-electric future.

Ground source water to water heat pumps were used as a central heating/cooling plant for the building, and zone level air handling equipment receives ground source water directly for direct cooling without compressor energy. Around the clock (24/7) cooling loads were handled with water to air heat pumps to reject heat to the ground loop and water to water heat pumps. Centralized DOAS heat recovery unit with 90% energy recovery coupled with an efficient envelope allowed a central plant sized at 14 Btu/SF. Zone level ductless fan coils sized for low heating water temperatures further improved central plant efficiency, capacity, and reliability. All of these combined measures helped deliver a critical SPU facility that was zero net energy ready, and poised for consistent operation.

Owner: Seattle Public Utilities
Scale: 14,000 sf
Completion: 2017
Energy Utilization Index (EUI): 22
Hours of Operation: 70-hour work week with 24/7 capabilities


Operating in a dense urban environment where buildable land is limited, the district activated its masterplan to centralize services. The transportation maintenance facility was the first phase of the plan to concentrate coach service and maintenance functions along with administration, dispatch, and training spaces. While these are vastly different operational uses than the rest of the owner’s building stock, they offered unique opportunities for innovative solutions.

Maximizing efficiency and minimizing maintenance, ground source water to water heat pumps were utilized to centralize heating/cooling equipment for the building. Solar hot water heating system augments the ground source heat exchanger system capacity when the heat pumps are in heating operation and provides “charging” of the ground source well field all year long. Additionally, ground source water is piped directly to air handling equipment for direct cooling without compressor energy.  This all-electric building has multiple facets of energy saving systems all geared towards minimizing electric energy consumption and maximizing equipment operational reliability for this essential facility.

Owner: Bellevue School District
Scale: 33,645 sf
Completion: 2012
Energy Utilization Index (EUI): 12.2 excluding PV; 8.4 with PV
Hours of Operation: 7:30 a.m. – 5:00 p.m.
ASHRAE Regional Tech Award / Industrial, First Place
ASHRAE Regional Tech Award / Ralph Robson Award