Christ Church

Designing and Installing a New, Comprehensive HVAC System

Built between 1767 and 1773, Christ Church was the first Episcopal church in Alexandria, Va., and a place of worship for many prominent historical American figures, including George Washington, Robert E. Lee, George Mason, and many U.S. presi­dents. According to legend, George Washington, while standing in the Christ Church graveyard, announced to his friends his intentions of fighting for American independence against the British.

In 1970, Christ Church was designated as a U.S. National Historic Landmark, and was added to the U.S. National Register of Historic Places. The church draws thousands of visitors each year who take walking tours that feature the church’s interesting architectural features and unique history. Today, Christ Church has more than 2,500 members and is comprised of three buildings—the church building, Parish Houses, and Fowler House.

The HVAC system was the most comprehensive and expensive system the Church owned, and its church building and adjoining Parish House had several systems that together provided air conditioning, heating, and limited ventilation. Its main systems—dating from 1950 and with parts of it remodeled in 1987- 89—were becoming increasingly antiquated and unreliable, with many components failing on a regular basis.

“All in all, our failing HVAC system was having a profound impact on many aspects of life at Christ Church,” Barry Stauffer, chairman of the Church’s HVAC committee, said. “Outside technical expertise was required to manage the controls; there was no central monitoring or control; and temperature and humidity could not be adequately controlled, which negatively impacted the comfort of our congregation as well as the working condition of the piano and organ and the church interior.”

The RM Thornton design-build project kicked off with a pre-design meeting to identify all the factors that would impact the project’s time to complete and overall cost. These factors included: the history of the church’s current HVAC systems and the number of parts and components that required replacement vs. refurbishment; the church’s needs for normal operation during construction; its priorities for construction phasing; and possible, serious disruptions to church operations during construction.

RM Thornton and their sub-contracting team of engineers and architects then presented four options to church leadership. For each option, a life-cycle analysis and schematic design were developed that addressed the many priorities and challenges of the project, including architectural impact, aesthetic integrity, energy consumption, total ownership cost, and potential operational disruption.

Members of the church’s construction committee selected a variable air volume (VAV) system as the best solution for the church. The design chosen is one in which water is chilled or heated centrally and piped to various buildings, where air is then blown across heat exchangers to cool or warm the interior space.  The VAV design was chosen because of its low impact on the church’s architectural features, its reliability using tried and true technology, and its lowest initial cost and projected lifetime cost of the four options considered. It also was the best option for achieving significant reductions in energy usage and carbon emissions, and the simplest option in mechanical design, which means it will have the fewest ongoing maintenance issues.

The church made a major decision to have a chilled water system, where the entire air conditioning unit is installed on the roof. The system cools water to between 40 and 45 degrees Fahrenheit, and the chilled water is then piped throughout the building and connected to air handlers. The system also carries lower construction costs, reduced energy use, and requires less ongoing maintenance expense.

The RM Thornton design also called for re-using much of the duct work and piping between the Parish House and the Church to reduce costs of construction.

In January 2014, RM Thornton began its work demolishing the church’s old chiller, cooling tower, concrete pads, and pumps and installing new pads, and cooling tower piping. The project then moved forward in four phases: replacing the chiller and cooling tower; replacing air handlers in the church tower and basement with a new ceiling return air vent; replacing the Parish House’s boiler and air conditioning unit and installing new duct work; and replacing the Parish House’s remaining equipment and duct work. From start to finish, the project will take 13 months to complete at a cost of $2.5 million. Project completion is expected in January 2015.

“Upon completion, we will have a new HVAC system that is modern, greatly improved in reliability, and fully automated in its controls, as well as much more energy efficient,” said Stauffer. “We couldn’t be more satisfied with RM Thornton. This was a technically complex project and their team of engineers skillfully managed the many unique challenges we presented them.”