AT-84-06-3 -- Water-Source Heat Pump System for Mount Vernon Unitarian Church

An economic analysis of installed and future energy costs was made a new building designed for the Mount Vernon Unitarian Church, located in Fairfax County, Virginia. This analysis, conducted for several alternative HVAC systems, indicated that a water-source heat pump with a precooling coil would not only be the least costly to operate but would have the lowest installation costs. In this climatic area, heat pump systems are normally sized to meet the cooling load, which for this building was calculated to be 26.5 tons. Since the cooling coils share the load, it was possible to reduce the total size of the heat pumps to 14 tons. The COP in this system, both in the heating and the cooling mode, is substantially higher than an air-source heat pump system. A computer analysis showed that passive solar features can further reduce heating and lighting costs in an otherwise efficient building.