National Cathedral cool for hot summer

Special to CONTRACTOR Washington When a project is as massive as the National Cathedral, located here at the intersection of Massachusetts and Wisconsin avenues, other priorities can take precedence over year-round comfort. Thats the biggest reason the churchs air-conditioning system has taken almost 30 years to complete. The luke-warm emphasis on air conditioning is especially understandable when

Special to CONTRACTOR

Washington— When a project is as massive as the National Cathedral, located here at the intersection of Massachusetts and Wisconsin avenues, other priorities can take precedence over year-round comfort. That’s the biggest reason the church’s air-conditioning system has taken almost 30 years to complete. The luke-warm emphasis on air conditioning is especially understandable when the building’s age is taken into consideration. Construction on the National Cathedral began in 1907 (Teddy Roosevelt spoke at the dedication) and was completed in 1990 (the first President George Bush was on hand for the ceremony). Fortunately, the building’s trustees had the foresight to at least start installation of a cooling system BACk in the 1970s.

“It took 25 years to get the funding in place to complete the cooling system,” said Robert Reaves, president of Capitol Heights, Md.-based mechanical contractor R.M. Thornton. “The cathedral is such an awesome place, it’s just that other priorities kept coming up.

“Even though the original cooling equipment was installed in the mid-’70s, it is just like new, as it has hardly ever been used.”

A key element that affects the cathedral’s comfort is its limestone structure. In the summer months, when Washington can be hot and sticky, the cathedral does not reach its peak cooling load until about 5 p.m. Most other structures peak about 2 p.m. Because the structure is made of stone, and stone retains heat, the cathedral would never cool down during hot summer evenings.

R.M. Thornton started working on the cathedral’s hvac systems well before Reaves came to work for the company in 1975. His father, Frank Reaves, was president of R.M. Thornton in the mid-’60s when the contracting company was called in to complete the installation of the radiant heating system underneath the floor of the cathedral’s nave, or main worship area, begun by another contractor. The Episcopalian Church operates the multi-denominational facility.

As construction of the church’s West Tower progressed through the ’70s, R.M. Thornton installed components of the heating and cooling systems. The initial cooling equipment installed in the mid-’70s consisted of two 40,000-cfm air-handling units. The remainder of the system, which was installed in 2000, delivers the chilled water. This design/build phase included the construction of an onsite chiller plant, housing York International chillers as well as cooling towers and ice storage provided by BAC. The plant is located in a separate building below the cathedral. The system includes a series of pipes that carry water, cooled to 42° F, up to the main structure. The air-handling units help circulate the chilled air through the facility.

“The most recent project was done in two different stages,” Reaves said. “The chiller and ice storage was one stage; the other was retrofitting the air-handling units so they could accept the chilled water coils. We replaced those coils with more efficient technology.

“We were able to successfully marry the two phases to create a system that is not only efficient, but does not intrude on the architectural integrity or with sound.”

In fact, guides were conducting a tour in the nave last summer when the air-handling units came on, recalled project manager Curtis Wilson. “The docents conducting the tour made more noise than the A/C system when it was activated,” he said. “The fans didn’t interfere at all with the docents’ conversation.”

Both stages of the most recent project cost $2 million, including the state-of-the-art ddc controls system and electrical work. The job began in November 1999 with the A/C coming on last summer. R.M. Thornton still is working on one air-handling unit and providing cooling to the bookstore. The new air-distribution system has enabled the cathedral to maintain 72° F in the summer and improve the comfort level during heating months. In the past, summer church services were held in the early morning but not when it got too warm in the afternoon, Reaves said. Tours were conducted during the summer, but the cathedral was very warm. Now, the National Cathedral is one of the world’s only air-conditioned cathedrals.

“With this system in place, 300 or 3,000 people can attend services, weddings and state functions in the cathedral all year long, in comfort,” Reaves said.