Displaced Ventilation in Hospitals?

As facility operators continue to figure out where they fit in the green building movement it can be a challenge for building and system designers to help said clients choose what truly sustainable technologies make sense for their operations. To date, natural ventilation and displaced ventilation have gotten a lot of buzz in green designs, but never in association with hospitals—until now.


As facility operators continue to figure out where they fit in the green building movement it can be a challenge for building and system designers to help said clients choose what truly sustainable technologies make sense for their operations. To date, natural ventilation and displaced ventilation have gotten a lot of buzz in green designs, but never in association with hospitals—until now.

Two firms—Mazetti and Assocs., San Francisco, and Stantec, Vancouver, Canada—are working independently, but in concert with each other to develop displaced ventilation schemes specifically for hospitals. At the recent Green Build conference in Denver, the two firms presented their findings, Stantec on diagnostic and treatment areas, and Mazetti on patient and waiting rooms. According to Ray Pradinuk, a senior associate with Stantec Architecture, the firms were inspired by the health-care facilities of Europe, notably Norway, which employ a high degree of both natural ventilation and natural lighting.

In the United States, according to Bob Gulick, P.E., with Mazetti's Portland, Ore., office, what's hindered the implementation of displaced ventilation has been the fear of infection control, but their work, to date, he said, suggests that the concept, typically employed for energy efficiency, should actually improve infection control.

In the case of Mazetti, its working with Kaiser Permanante on a test case in Modesto, Calif., that may be fully incorporated into a new facility the hospital is constructing in Hayward, Calif.

According to Pardinuk, health facilities are open to new concepts at this time because they're mainly interested in improving patient safety. “In Canada, for example, there are about 23,000 deaths in hospitals per year, but 37% of them have been found to have been preventable,” he said.

Beyond patient safety, indoor air quality and energy efficiency are also areas hospitals are interested in addressing. And thanks to a shift toward evidence-based design, administrators are more open to ideas which will address these concerns, which takes us full circle to the notion of displaced ventilation.

At the room level, the major sell of the scheme, according to Gulick, is a much better controlled air pattern.

In their trial design, Mazetti introduced conditioned air via displaced ventilation through a low sidewall configuration. In running computational fluid-dynamic (CFD) modeling, Gulick said they discovered an air pattern that's gotten many notable health-care experts nodding their heads in support, including renown infection control expert Andrew Streifel. He, according to Gulick, was among a number of guests the firm invited to participate in a charette to discuss the possibility the possibility of using displaced ventilation when they were commissioned by Kaiser Permanante to study the Hayward project. “To get the 50%-to-60% goal of energy savings associated with most green projects, you clearly need a responsive, well-integrated and thought-out building,” said Gulick.

Officials from California's Office of Statewide Health and Planning Development—OSHPD—which has a reputation for toughness, also participated. All were intrigued with the patterns of particle movement with the displaced ventilation scheme, according to Gulick, as CFD modeling proved air moved in a very distinct “piston effect” pattern vs. the completely random particle displacement found in traditional overhead HVAC designs.

Even though Hayward is in a mild Northern California climate, Gulick said they opted not to employ natural ventilation as they first wanted to study the air patterns, and set this technology up for more widespread use.

Stantec's research, on the other hand, focused specifically with natural ventilation and natural lighting in mind. For example, in seeking out models to study, the firm found some great projects in Norway and Spain. For example, according to Pradinuk, the diagnostic and treatment areas of Oslo Royal University Hospital feature 44% daylight with operable windows. The D&T block of an average Canadian hospital, on the other hand, he added, was only 24% daylight. Furthermore, a new hospital in Madrid achieved 55% daylighting and in doing so, created new kinds of family dynamic with new meeting and gathering areas.

In its scheme, scheme, Stantac is trying to marry use of windows with more natural ventilation to improve IAQ and patient morale. Much of their design centers on tree-lined courtyards. “We feel the view is very important and that green and nature-filled spaces are important,” said Pradinuk.

According to his partner, Paul Marmion, P. Eng., LEED AP., with Stantec Consulting, the firm's engineering arm, air intake for the design scheme draws air directly from these courtyards which should improve the oxygen quality itself. Specifically, outside air would be drawn into room via a floor level grill. No reheat would be employed, said Marmion, instead ceiling-mounted radiant heating and cooling systems—plus operable windows—would address patient comfort.

“That said, the system will have to be a hybrid, in that some sealed areas will still be required and slight negative pressure would be required to check air movement from the corridors,” he said.

Of course, much of this design is built on the notion that such a facility would operate in a mild, Vancouver-like climate where no augmented heating or cooling would be required for about 20% of the year. “This is really how European building ventilation has been designed for years. What's different is that we're adding controls to the equation to make it a more wholistic system,” said Marmion.

“But using natural ventilation would clearly be an energy premium, so we'd really need an emphasis on energy recovery and the internal facade system including [automated] shading,” said Marmion.

But perhaps the most radical notion in both Stantac's and Mazetti's hospital ventilation scheme of the future is the idea of actually cutting back the number of required air changes per hour to only four from the traditional six. According to Gulick, they feel four air changes with 100% outside air is better for infection control than six overhead changes with recirculated air.

Of course, the notion of doing less air changes per hour is completely counter to current practices and code requirements. Therefore, the next step, he said, is getting information on the design to the various code authorities so it can be implemented. “But so far, the feedback we've gotten from both projects, particularly regarding the particle flow, has been a huge sell,” said Gulick. “And less air changes means better energy savings, better IAQ and better patient comfort.”

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