A rigorous simulation of all options, including various sizes of heat pumps supplemented by gas boilers, showed an economically optimal configuration. With this system, heating and cooling water supply and return piping would connect chiller and boilers to fan-coils for each room or zone. Outdoor ventilation air was supplied from central station constant volume air handlers ducted to the return air plenum of the fan-coils. The capital cost analysis proved to be conservative in that the heat pump fan-coil system tender cost was 22 percent below the budget. The single 108 ton geothermal heat pump will satisfy approximately 80 percent of the school's heating needs, even though the heat pump was sized at only 30 percent of the design heat load.
Supplementary heating is provided by high efficiency gas boilers.
Annual consumption of the final design was 1,001,333 kWh electricity and 2,269 GJ natural gas. The final design also incorporated double pane tinted glazing , T8 light fixtures with electronic ballasts, photocell control of lighting in clerestory areas and occupancy sensor control of lighting in classrooms. The McMath School design team, having considerable experience in hydronic systems, had few new challenges incorporating the heat pump itself in the design, even though only Gordon Shymko, the energy and mechanical design team leader, had extensive experience with GeoExchange. The new element to all was the design of the outside collector field. CSLM Associates of Kanata, Ontario was retained to advise the team.