Located in Washington State’s Puget Sound, Bainbridge Island is home to a highly regarded school district. In replacing Captain Johnston Blakely Elementary School, the Bainbridge Island School District sought to create a space with adaptable, diverse learning environments well connected to the surrounding forest.
Working with Mithun, the project team supported the design of a visionary new facility to replace the existing school, which had been built in 1965. The new Captain Johnston Blakely Elementary School features 20 classrooms and shared learning spaces divided into clusters, for everything from STEM to art and music classes.
Having previously worked with the Bainbridge Island School District on the award-winning Wilkes Elementary School, Arup was tapped to design creative heating, cooling, and lighting solutions symbiotic with the natural environment. The success of the design approach at Wilkes, especially the ground source heat pump, led to the same approach to be selected by the school district and design team for Blakely.
To conserve resources and minimize environmental impacts, the design incorporates high performing systems, including a ground source heat pump, natural ventilation, and daylighting throughout the school.
2 storybuilding in step with slope
Well-mapped daylighting and ventilation design
The Bainbridge Island School District wanted to ensure equitable access to the outdoors for all students, which presented a challenge for a two-story structure. In response, the project team developed a concept to allow for natural ventilation and daylighting on both levels of the building. The solution employs operable windows in all classrooms, skylights on the second floor, and ventilation shafts coordinated throughout to provide a relief path for the ground floor classrooms. These shafts also serve as the path for solar/daylighting tubes, affording natural light to students on the first floor as well as to the kitchen. Skylights are also featured in the cafeteria, gymnasium, library, and administrative wing, all of which allow for minimal electrical lighting.
Window locations were carefully considered, with some in corners and others along the length of a wall, to optimize daylighting. When windows are opened, cross ventilation results in a lower CO2 level in the room, which automatically modulates down the mechanical system equipment.
An efficient ground source heat pump
Arup designed a ground source heat pump to supply most of the school’s heating and cooling needs. The system, which relies on a borefield with 40 wells drilled 300-feet deep, makes use of the stable ground temperature for heat absorption and rejection, saving the district energy year-round and eliminating the need for unsightly exterior mechanical equipment.
Ventilation where required
The airside systems serving the classrooms are configured as a dedicated outdoor air system (DOAS), meaning ventilation air is provided directly to each space, rather than mixing with the building’s return air. This system type provides superior indoor air quality as air is not mixed between spaces. Because of this, Arup was able to negotiate an exception to the code requirement that the return be fully ducted with the local health authority, saving significantly in costs. Heat wheels installed in each DOAS unit provide further efficiency to the project by tempering the incoming outdoor air with outgoing exhaust air.
Blakely uses a hybrid deep-bore ground source heat pump, with a backup electric boiler, for heating and cooling. A propane generator is provided for emergency loads but is not intended to be regularly used. Key factors in selecting an all-electric system for this school included lowering operational carbon, and the high relative cost of gas on Bainbridge Island. With that, the ground-source heat pump system has an excellent payback period (less than ten years), which drove the HVAC system selection.