The Solutions
The renovation of Bruton Parish Church balanced historic preservation with the need for modernized, energy-efficient mechanical systems. Hosting weekly services, and welcoming visitors for tours and educational programs, the church required updates to accommodate its diverse occupancy patterns. CMTA utilized Trane Trace 700 modeling software to simulate the building’s energy performance, incorporating precise occupancy schedules. However, the building's age presented significant challenges in accurately modeling its construction properties. To overcome these difficulties, CMTA developed custom construction types to better represent the walls, windows, and doors, enabling more accurate energy models. These models informed strategic updates to the building envelope and mechanical systems, which included the installation of a geothermal HVAC system, water-to-water heat pumps, and programmable thermostats.
Heat exchange in the original system utilized water from a well located within Colonial Williamsburg, creating a functional but dated system for regulating the building’s temperature and air quality. Aiming to modernize the mechanical systems while preserving the church’s historical integrity, the design team replaced the existing chiller and boiler configuration with two water-to-water heat pumps. This new arrangement drastically improves efficiency and offers more flexibility, with a smaller heat pump meeting the church’s load during off-peak hours or when unoccupied, and a larger unit available to handle peak demand when the building is fully occupied. Additionally, to install the closed-loop geothermal system, drilling was carefully performed at the Palace Green—an untouched and historically significant area of Virginia’s first capital—ensuring that the historical land on the church grounds remained undisturbed.
One critical issue discovered during the renovation was a malfunctioning damper, which had been stuck open, allowing excessive intake of fresh air into the system. This limited the system's efficiency, particularly during the winter months, as it struggled with improper dehumidification and higher-than-expected temperature differences. The damper was replaced, restoring proper air intake functionality and resolving these inefficiencies. Additionally, outdated humidification equipment was replaced with a modern electric steam humidifier, enhancing thermal comfort and ensuring reliable humidity control. Further measures included contracting a duct cleaning company to maintain cleanliness in the air distribution system, which utilizes underground brick tunnels that naturally maintain a stable temperature of approximately 60°F year-round.
Together, these upgrades not only optimized heating and cooling during non-peak hours but dramatically reduced the church’s site EUI from 395.6 kBtu/ft² to 117.2 kBtu/ft², achieving an impressive 237% reduction in energy consumption.
