Radiant HVAC Approach Cools Tucson Hospital
Banner Health’s 672,000-sq-ft hospital in Tucson is the first in Arizona to implement chilled beams for patient rooms, but it’s the tower’s mini-central plant taking up the fourth floor that makes the facility one of a kind.
“The fourth floor is everything,” says Charlie McGowan, mechanical engineer at AEI | Affiliated Engineers. “The idea is to centralize utilities and the bulk of maintenance work, to park staff there and they don’t need to be in patient spaces.”
The $300-million project is the biggest in Tucson history. It adds to the existing medical center, previously only associated with the University of Arizona medical school. A joint venture partnership between Sundt and DPR is the contractor for owner Banner Health, which is building the new hospital through an agreement with the university.
Scheduled for completion in April, Banner University Medical Center Tower (BUMCT) has 204 patient rooms, 20 imaging suites, 21 operating rooms, 12 delivery rooms, 120 medical surgery rooms and 72 intensive care rooms. A kitchen and dining room will replace food-service facilities currently located in the university’s existing hospital.
Construction began in early 2016. Shepley Bulfinch of Phoenix and GLHN Architects and Engineers Inc. of Tucson are the architects. Brittany Burbes, project manager, Sundt | DPR, says the project is technically a standard guaranteed maximum price project but the team operates “IPD-like without the contract.” The construction and design team worked together at the Diamond Children’s Medical Center, which is connected to the new tower, easing access between their shared space and the construction site.
The onsite construction team, including subcontractors, peaked out at 750 people in early 2017, with 200 currently working on the project, says Djuro “Judo” Rosic, superintendent at Sundt | DPR.
Fourth Is First
McGowan says a myriad of factors prompted a non-standard approach to the HVAC system’s design and construction, led by Sundt and DPR. Most hospital project teams place HVAC and electrical equipment in the basement or on the roof. But the medical tower’s plans didn’t include a basement, and the roof was impractical since the nine-story building is planned for an additional two floors in the future.
The tower’s fourth floor includes 14 air-handling units, an energy recovery unit, two steam boilers and a 350-ton booster-chiller for dehumidification, McGowan says. The main normal and essential power electrical rooms, as well as the pneumatic tube blower room, are also located on the fourth floor. The air handlers move 640,000 cu ft per minute and the energy recovery unit moves 225,000 cu ft per minute.
Eight accessible shafts on the fourth floor also provide access to variable air volume boxes in third-floor operating rooms. As a result, maintenance workers don’t have to enter the rooms, keeping them from having to put on “the bunny suit” in order to prevent contamination, says McGowan.
The building contains about 500 tons of ductwork, with 250 tons on the fourth floor alone, Rosic says. One of the largest ducts on the fourth floor is 180 in. wide and 78 in. high, with several others in excess of 150 in. in width. McGowan says using chilled beams and other forms of radiant heating and cooling reduced duct size, saving space on the fourth floor.
The team’s plan for radiant heating and cooling began at the concept phase, McGowan says. Banner Health is also building a hospital tower in Phoenix with a traditional HVAC system. The construction and design team at BUMCT decided on radiant cooling and heating featuring chilled beams. He says worries about moisture control are not a factor with the built-in capability to dehumidify when necessary.
“As an industry, we are realizing buildings are tight, and when we use air handlers for moisture control, there are typically no issues,” he says, adding, “typically in a patient room you don’t see a lot of latent patient loads. There just isn’t that much moisture that would require significant air to dehumidify.”
He says the BUMCT’s chilled beam system, approved in 2013 per ANSI/ASHRAE Standard 170-2013 for use in patient rooms, provides two outside air changes per hour.
The radiant approach is not just exclusive to chilled beams in the patient rooms, however. The lobby also includes passive and active chilled beams as well as a cooled and heated slab. Hot and chilled water is brought to the lobby slab via 2-in. pipes from the fourth floor. The water then runs through the floor via cross-linked polyethylene, or PEX, pipe. In order to provide moisture control, the chilled water is kept above the dew point, typically at 55 to 57 degrees.
Change Order: Central Plant
When the project was designed and conceived, chilled water and other utilities for the tower were to be provided by existing University of Arizona central plant operations. However, in mid-2016, Banner requested a $28-million change order to build a new central plant to serve the tower and three other Banner-operated buildings on the campus, says Jeremy Kwapich, senior project manager at Sundt | DPR. To meet the April 2019 opening date, the team built the central plant in 12 months about 200 yards from the tower.
To serve the hospital and three other Banner buildings, the central plant uses 6,000 tons of its 9,000 tons of chilled water capacity. Three engine generators currently provide 6 MW of electrical capacity, with space for an additional three. Boiler capacity is approximately 84,000 mbh, or thousands of BTUs per hour.
The Banner-owned and operated central plant allows for utilities to arrive from a single location, McGowan says. However, since the new central utility plant serves new construction as well as older buildings, one of which is shared between Banner Health and the university, the two entities had to negotiate whose utilities were to be used where.
“It was a year-long process to do the legwork and then making sure what we thought was appropriate was what Banner and UA wanted. This required significant collaboration between Banner Health and UA,” McGowan says.
The construction team was dedicated to running a paperless project from the start, with full buy-in from the city of Tucson. BUMCT was the first project to go through the permitting process electronically, says Kwapich, with iPads ubiquitous among project personnel. Change orders are reviewed in BlueBeam and then sent to the architecture teams.
“We tell our subcontractors to update early and update often,” says Rosic.
Burbes says the all-digital plan process saved time and money, adding that the team leaned on vConstruct, a DPR subsidiary in India, to perform split sheets and RFIs.
“They did that overnight for us, so we always have an updated form of documents,” she says.
Digital plans also helped mitigate the added complexity of using many specialty contractors, even from within the same specialty. Kwapich says the construction team had to compete with two nearby large projects that strained the capacity of local specialty contractors. So, Sundt | DPR began working with specialty contractors early in the process.
“We had to be upfront and tell them what the needs were. If they were going to be too busy, we had to tell them no,” says Burbes, adding the prefabrication was also key to meeting the tight construction schedule.
Patient rooms have prefabricated headwalls from Amico Corp. To handle UL-rated medwalls, the construction team created a prefabrication area on the third floor. The prefabricated operating rooms include CleanSuite ceilings made by Nortek Air Solutions, Burbes says, and the typical universal operating room design provided 3,960 cu ft per minute of laminar flow, lighting and boom supports. The OR ceilings were prefabricated and finished in a four-part assembly and installed in two days.
“If we did not do all of the prefab, we wouldn’t have met the schedule,” says Burbes.