A hospital’s goal to achieve net-zero energy isn’t impossible, but it’s an effort that requires a combination of active and passive systems and community partnerships.

That was the message from Kim Shinn, a principal and senior sustainability wizard at TLC Engineering for Architecture, Brandon Bardowsky, director of facilities at Martin Health Systems, and Roy Gunsolus, principal at HKS Architects, during their session at the Healthcare Design Conference in Washington, D.C.

To come to that conclusion, the panelists shared how they took two LEED-certified healthcare projects and asked, “How would the designs have differed if the owners’ original intent had been to achieve net zero energy use?”

As part of their process, the team decided that first they would look to reduce energy use as much as possible using passive systems, before considering active and renewable solutions, such as chilled beam systems or solar panels.

The two projects—Texas Health Presbyterian Hospital in Flower Mound, Texas, and Tradition Medical Center in Port St Lucie, Fla.—had already hit some impressive numbers as part of their LEED design efforts. For example, Texas Health’s 184,000s-square-foot facility had reduced energy consumption by 15 percent using efficient HVAC and lighting systems. Tradition Medical Center had set a goal of 150 kBtu per square foot per year as part of its energy budget and had achieved 149 kBtu.

One of the ways the team sought to further push the envelope was looking at energy consumption by end use. One of the biggest findings was the amount of energy used by each hospital for reheating: 69 percent at Texas Health’s facility and 37 percent at Tradition Medical Center. “Reheating is our enemy,” Shinn said. “That’s what we want to attack when we’re going after energy reduction in hospitals.”

The team shared a number of energy conservation measures that can be used to reduce reheat, and pinpointed a few for their effectiveness, including better control strategies for air flow in occupied and unoccupied spaces; heating hot water temperature reset; active chilled beams; water-side heat recovery; and air-side heat recovery with dedicated OA system.

For example, the speakers suggested that hospitals can reduce hot water temperatures based on what’s going on outside, taking advantage of summer weather to lower the temperature on non-domestic water sources to less than 120 degrees—a move that saves 40 times the energy use compared to increasing roof insulation, Shinn said.

By implementing some of these strategies on the two projects, the team proposed new energy use intensity (EUI) projections that saw 62 percent energy savings at Texas Health and 46 percent at Tradition Medical Center. “This is nothing that we can’t do with our current tool kit,” Shinn said.

But their work didn’t stop there. The team also turned its sights to renewable energy systems to see how those could impact the two projects. Regarding solar radiation, the team looked at the potential of mounting PVs on the building, but found it to be impractical based on the size and cost of the installation necessary to provide enough energy generation.

Another option--combined heat power (CHP)—seemed like a more viable option but would be too expensive for a hospital campus alone, so the team looked at the feasibility of a hospital partnering with biomass producers, including dairy or cattle farmers, to produce waste than can be turned into methane for electricity generation. For example, Texas Health’s Flower Mound facility was located a few miles from a cattle feed operation and Shinn said that locating a biomass facility at the ranch could generate 1MW of electricity to offset the energy the hospital is pulling off the grid. “The moral of the story is it takes a district to achieve net zero,” he said.

Another lesson on the project was the return on investment. Looking at the proposed cost breakdown, including construction cost, proposed net zero value, annual energy cost avoided, both projects would have an ROI of 9-13 years—far above the goal of a five year payback. However, considering the life of a hospital building, Bardowsky said “it’s not out of the range of possibilities.”