Doing Justice to a Green Courthouse Renovation
Modernization of the 1960s-era Byron G. Rogers Federal Building and U.S. Courthouse in downtown Denver is putting new chilled-beam technology to work to help reduce energy use in the building’s office tower by almost 70%.
Work on the 18-story, 494,000-sq-ft building, home to 11 federal agencies, includes upgrades to structural elements and all major building systems, including mechanical, electrical and plumbing. Built in 1965, the tower’s inefficient and inflexible mechanical system will be removed and replaced with a chilled-beam system. Chilled-beam technology has been used extensively in Europe but is just making its way to the U.S., says Bill Green, president of The RMH Group, Lakewood, Colo., the mechanical-electrical engineer.
The chilled beams use moderate temperature water, with a small amount of air, to heat and cool the building. The system, along with a high-efficiency central heat-pump chiller, captures heat generated in the building during the day by people, lights, computers and sunlight through windows. The heat is stored in a basement thermal tank and circulated through the chilled beams during morning warm-up, Green says.
The water that runs through the chilled beams at night heats the building 10 to 20 times more efficiently than using conventional gas-fired boilers. It results in a 75% reduction in energy used to run fans because the need for cooling or heating large volumes of air is eliminated and the system uses the waste heat that would normally be lost, he says.
The building’s energy use per sq ft is anticipated to be extremely low, at 27 kBtu per sq ft per year, Green says. With the addition of a solar photovoltaic system, the number is expected to drop to 25 kBtu per sq ft per year—a 66% energy consumption savings compared with other office buildings in the region, Green adds.
The $136-million design-build project features envelope upgrades, solar thermal hot water, 100% LED lighting and double-glazed, low-E, gas-filled high-efficiency windows for the adjacent five-story, 126,000-sq-ft courthouse. Mortenson Construction and architect-of-record Bennett Wagner & Grody, both in Denver, are partnering with design architect HOK, St. Louis.
Structural engineer Martin/Martin Inc., Lakewood, Colo., is working to bring the office tower into compliance with seismic and progressive collapse criteria.
Mike Owens, General Services Administration recovery executive, says the modernization plan had been on GSA’s radar for 10 years, but American Recovery and Reinvestment Act funds made it a reality.
The complex is scheduled for placement on the historic register in 2015, so the exterior will be left untouched to preserve its facade. Window frames and existing precast will be left in place and all window work will be done from the inside.
Blast consultant Martin/Martin is working to bring the office tower into compliance with current seismic and progressive collapse criteria.
Mortenson project manager John McCorkle says a new high-performance wall will be added on the inside that includes double- and triple-pane windows, drywall framing, spray-foam insulation and a semi-rigid mineral-wool insulation board.
“We’re pushing the envelope to do the right thing while keeping the historic nature of the building intact,” McCorkle says.