Applying Passive House Design Principles to Labs and Hospitals

The Passive House building standard is considered the most rigorous, voluntary energy-based design and construction standard in the industry. Consuming 40 to 90 percent less energy than conventional buildings for heating and cooling, Passive House traditionally has been used in single-family homes, commercial buildings, schools, and office buildings, but the standard is making new strides toward application in energy-intensive laboratory buildings as well. While achieving true Passive House-level performance in a large-scale lab facility is still a far distant (if possible) goal, many of the standard’s fundamental design approaches can be used to significantly reduce energy consumption while improving occupant comfort and air quality.

“Passive House is not passive in that it doesn’t have any systems in it,” explains Matthew Fickett, associate architect at Boston-based Perkins+Will. “It’s a building where the envelope is so robust that when you use a little bit of energy to heat or cool it, that little bit of energy goes a much longer way, because the envelope is super-insulated and it keeps all of that energy inside.”

One of the key metrics considered when certifying a building as Passive House is the facility’s source “energy use intensity” (source EUI), which expresses a building’s energy use. The challenge is that, while a low source EUI indicates excellent energy performance, certain types of equipment-intensive and continuous-operation buildings—like labs and hospitals—will inevitably use more energy than homes, offices, or schools. For a building to receive Passive House certification through the Passive House Institute (PHI) using today’s version of the standard, the source EUI must be below 38.1 kBtu per sf per year. The reality is that source energy for many labs is well above 300 kBtu per sf per year, due to the intensive equipment and capacity demands. This means that achieving current Passive House targets for a lab at scale is essentially unachievable, but the conversation around defining what the appropriate metrics for labs should be has been gaining traction.

“It is really difficult for a lab to get to 38.1. We’re just not going to achieve that. But there are some really important concepts to discuss here in terms of moving in that direction and ultimately bringing the two worlds together,” says Fickett. “It isn’t just a matter of having a conversation about how labs can get down to 38.1 kBtu, but also how Passive House can open that conversation up to have a realistic dialogue around what the requirements should really be for these types of buildings.”

Passive House Parameters

In addition to source EUI, the other metrics used for scoring a Passive House project include the total heating and cooling demand—which is established based on the specific region and climate of the facility—and the envelope airtightness, where the target is 0.6 air changes per hour (ACH), at 50 pascals.

“Airtightness is measured once the building is constructed, so you shut everything down, install the blower door, and get it up and running to measure it,” says Fickett.

The Passive House standard addresses four key categories: space heating and cooling, total energy use (source EUI), airtightness as a measure of envelope performance, and thermal comfort. To receive Passive House certification, a project must pass the blower-door test on the completed building to illustrate compliance with the airtightness requirement, and demonstrate compliance with the heating, cooling, and source EUI energy allowances through an energy model. To achieve the energy allowances, projects typically will feature super-insulated walls, optimized ventilation systems, and ultra-efficient HVAC and lighting equipment. In addition to having a robust envelope, condensation is not allowed, and ventilation systems are required to be neutral.

“Neutrality means that there is no air pressure trying to push or pull anything through the envelope. Basically, whatever you put in, you have to take out. So, there is no risk of air moving through the building and creating holes,” says Fickett.

One challenge for applying the standard to lab spaces is that windows are required to be operational. This means they likely need to be mixed-use buildings, not just labs.

“There is a perception that Passive House buildings are hermetically sealed, and that is not the case at all. One of the key factors in the methodology is the idea that when it’s possible to open windows to mitigate heating or cooling demand, you should take advantage of that. And we’ve found that scientists really like to be able to sit at their desk and open their window. This is an opportunity in newer lab buildings where offices and collaboration spaces are being located at the perimeter of the building, outside the controlled laboratory zones,” says Fickett.

Another big challenge is equipment load. Labs inevitably have higher internal heat gains and equipment electricity use than other buildings due to the need for things like storage freezers and imaging equipment.

“Generally, there is an understanding that labs create a whole bunch of internal heat load. They use a lot of equipment and have really high ventilation density,” says Fickett. “The way Passive House has dealt with that to date is to essentially say: ‘We’re going to tell you what we think the allowance should be for the plug loads and heat gain of your equipment, and that is what you put in your model, but it is going to be less than what is actually happening.’ So, when the model spits out 38.1 kBtu, that is not indicative of what is actually happening in the building. We would like to change that conversation to really look at what the target should be for Passive House when it’s applied to lab buildings.”

Passive House for Labs

While some elements of Passive House will need to be reevaluated for practical application in lab facilities, many of the principles are already being applied. Chief among those is a robust, airtight envelope. The downside to having a super-insulated envelope is that capital construction costs are typically higher.

“In terms of what Passive House potentially means for labs, the envelope and thermal comfort of the perimeter are clearly important,” says Julie Janiski, an associate principal at BuroHappold Engineering.

“People have this idea that the envelope isn’t a significant load,” says Fickett. “Also, if you try to put operable windows in a lab, people look at you pretty funny. It is generally not done. But the people who benefit most from being next to a good envelope are not those working in the tightly controlled lab spaces. They are in the offices, classrooms, and write-up areas. It is already common to design buildings this way—with the lab spaces on the interior and the office and collaboration spaces along the perimeter—but we think this approach is strongly supported from an efficiency standpoint, as well.”

Ventilation in lab environments is typically driven by fume hoods, where the normal strategy is to fill the building with the needed fume hoods and establish the amount of required makeup air from there.

“We normally set the ventilation for a lab based on the quantity of air required, and then we look at what is done with that air when it’s leaving the building. We think there is a huge story around contamination control and what it means in a lab. And that can drive a really productive conversation with clients about the importance of doing blower door testing and having the construction quality control to make sure your envelope doesn’t let random bits of air in or out of the controlled lab spaces. We already have standards for air infiltration that are not that far off from what Passive House requires, but it doesn’t get a lot of attention,” says Fickett.

“We want to have energy recovery on the ventilation system so that energy is not thrown away. We also want to have energy recovery on a heating and cooling system that provides simultaneous heating and cooling to save energy, for example, by taking the heat rejection from the lab spaces that require cooling and transferring it to other spaces that require heating in the winter,” says Janiski.

Energy recovery systems designed to capture energy from the outgoing airstream and use it to condition the incoming airstream can also be a conceptual hot-button issue for lab owners.

“Energy recovery is something a lot of people get nervous about, because you have lab exhaust coming out of a building and fresh air coming in that everyone is going to breathe. So people worry about cross-contamination. But now the new codes are starting to require it, and energy recovery equipment is available where the airstreams do not mix,” says Fickett.

One of the most popular solutions for energy recovery in heating and cooling is a variable refrigerant flow (VRF) system. This all-electric technology consists of an outdoor condensing unit combined with multiple indoor units that serve various building zones when connected by refrigerant-filled piping. VRF systems offer multiple benefits, including minimized ductwork, interior zoning with individual temperature control, and eliminating the need for secondary chilled or hot-water distribution.

“The idea behind VRF is that once you’ve spent energy to make heating or cooling energy inside your building, you shouldn’t throw it away just because it’s in the wrong spot when you can move it to where you need it,” says Fickett.

Over-sized capacity is another issue in labs where the goal is to plan for future flexibility. In one recent case study looking at the measured equipment loads of a finished clean room, the expected energy use during the design process was around 100 watts per sf, while the operational reality ended up being more around 8 watts per sf. This implies that a significant amount of inefficiency was built into the capacity of the building.

“In that case, it was not just oversized by a few percent. It was oversized by orders of magnitude,” says Fickett. “The challenge is that there is a clear operational penalty if the owner moves in and they can’t serve the load they need, but there’s no penalty if you’ve oversized the systems. Energy codes require a certain efficiency in your cooling equipment, but they don’t say anything about sizing the equipment.  So you can install a high-efficiency system sized for a load 10 times what actually is needed and still be code compliant.”

“Obviously, we don’t want to walk away from a building and not be able to give them something they might need in the future as science and technology change,” adds Janiski. “But there are lots of options for modular MEP and HVAC solutions that allow you to set up a system that is right-sized from the get-go with the ability to add system components as you need them down the road. Two key reasons for this are: A, there is a first-cost savings in this approach; and B, when you install right-sized systems, they run more efficiently.”

Case Studies

The small, rigorously designed 2,450-sf Warren Woods Ecological Field Station at the University of Chicago, located an hour outside of Chicago, was distinguished as the first Passive House-certified lab in the world. To achieve this, the design team at GO Logic, along with mechanical engineers, JH McPartland and Sons, worked in direct collaboration with the Passive House Institute to define parameters.

A larger-scale example of applying Passive House design features is the Spaulding Rehabilitation Hospital in Boston. Hospitals are similar to labs in the extensive amount of equipment and 24-hour operational demands of the facility.

“Thanks to a robust envelope with triple glazing, we were able to omit the perimeter fin-tube heating system in that facility,” says Janiski. “So the cost model for the project worked out to support a robust envelope that ended up doing a lot of good things for everyone involved.”

Another recent example is The House, a multifamily residential tower on the Cornell Tech campus on Roosevelt Island in New York. The House—on which Janiski served as engineering project manager—is the largest, tallest, Passive House-certified project in the world. In that case, the massive scale of the building worked in its favor. Since the ratio of the envelope to the amount of enclosed floor space was much smaller than in a single-family home, it allowed the building to achieve much more consistent comfort control across the entire building using less energy.

“It was a huge learning curve for all of us on the project team, as well as the Passive House Institute, in terms of how to take their standard and apply it to a large multifamily project at scale,” says Janiski.

“One of the big takeaways in this model is that the envelope does matter. Don’t let anyone tell you it doesn’t,” says Fickett. “Also, the code is already headed in that direction. The newer version of ASHRAE 90.1 requires you to prove your envelope infiltration rate with testing, so it is not really that far behind Passive House, which means you’re going to have to start doing this sooner or later.”

By Johnathon Allen

Environmental Building Standards:

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Courtesy of Perkins+Will and BuroHappold

Passive House is a voluntary building standard that primarily addresses energy use and envelope airtightness. To be certified as Passive House through Passive House Institute (PHI), a building must not exceed an annual heating and cooling demand based on location and climate using the Passive House Planning Package. Total primary energy (source EUI) must be under 38.1 kBtu/sf/yr. And the building must not leak more air than 0.6 times the volume per hour at 50 pascals, as tested by a blower door.

LEED (Leadership in Energy and Environmental Design) is a building standard established by the United States Green Building Council (USGBC) to gauge the environmental impact of a building. There are four rating levels: Certified, Silver, Gold, and Platinum. Buildings earn LEED points for various sustainability features, including energy-saving technologies, waste recycling, water efficiency, indoor environmental quality, and use of local materials.

WELL is a performance-based building standard that measures features impacting occupant health and wellbeing. Categories include air and water quality, sound quality, amount of natural light, and healthy eating areas. Building performance is assessed after occupation by independent third-party assessors using rigorous health-based standards. Rating levels are Silver, Gold, and Platinum.

RESET is a building certification standard that focuses exclusively on indoor air quality. Unlike LEED and WELL indoor air quality testing—which is completed in one day—RESET gathers data over three months using real-time monitors and requires annual recertification.