How to design proper exhaust and air handling units in laboratories, part 3
Brandon Fortier and Jeremy Barrette answer questions about labs and research facilities
- Consider the owner’s project requirements and what HVAC products or systems can help achieve them.
- Review lab and research facility example design strategies.
Air handling insights
- Laboratories use a lot of energy, highlighting the need for constant air cycling depending about the lab needs.
- Different labs will need to meet different exhaust environments.
Air handling units are an important part of cycling air through spaces. Brandon Fortier, IMEG’s National Science and Technology leader, and Jeremy Barrette, principal at Affiliated Engineers Inc., walk us through different instances of exhaust and air handling unit systems, as well as examples in this partial transcript from the Aug. 11, 2022, webcast “HVAC: Labs and research facilities.” This has been edited for clarity.
Brandon Fortier: Labs are very large energy users, and one major reason for that is the quantity of outside air that is required in a laboratory environment. When you have laboratories with chemical hazards, biological hazards, there’s a lot of exhaust that needs to be implemented into the facility, which requires a bunch of outside air for makeup.
One thing I consistently see, especially in older facilities when we’re going to do renovations, is previous engineers separated the air handling unit systems for laboratories versus non laboratory spaces. That certainly works from a functional standpoint, but it’s not the optimized solution from an energy standpoint.
Laboratories and offices are going to have ventilation requirements usually for labs that’s driven by the exhaust air requirement and makeup air, and that becomes a once-through system. So, if we’re exhausting in 1,000 cubic feet per minute (CFM), we need to be bringing in 1,000 CFM of outside air as makeup for that system. Offices are going to have a ventilation requirement usually dictated by code or an ASHRAE 62 standard. If those are on separate systems, we’re bringing in a bunch of ventilation there to do both of those systems, both of those needs.
However, if we combine those systems, we put the laboratory and the office on the same system, it eliminates some of the ventilation we need to bring in at the building level. We’re able to transfer return air from the office into the laboratory to serve as makeup air.
Instead of having to bring in 100% outside air for the laboratory, we can maybe bring in 80% of the exhaust flow rate in outside air and transfer that other 15% or 20% in from the office. That reduces the overall level of ventilation and outside air that needs to be brought into the building, reduces your heating and cooling loads for the facility.
Another thing we frequently run into is how to deal with exhaust. When you have chemical or biological laden exhaust air streams, we need to be very careful on what you do with that once it’s discharged to the atmosphere. If you’re in a big open field, maybe you’re only really worried about recirculating that type of exhaust into outside air intakes on your building. In an urban environment, there’s going to be buildings adjacent, there’s going to be pedestrians walking around. One tool that we found very successful is to use an exhaust dispersion analysis.
There are firms out there that can take your building, model it physically, put it into a wind tunnel and change wind velocities and directions to see exactly what’s happening to the exhaust as it leaves your building. You can do that to make sure that you’re not re-entraining the exhaust air stream into outside air intakes. You can do that to make sure it’s not settling on pedestrian areas. It’s really a way for those unique situations to make sure that exhaust is not being put anywhere but up into the atmosphere and away from occupied zones.
Obviously with laboratories, they vary greatly in what they’re doing. A high school laboratory is going to be a very different function than a research laboratory that’s operating 24/7, 365. The first thing from a system redundancy standpoint is to understand the type of facility you’re working with.
During the design phase, it’s extraordinarily important to understand the risks, look at makeup air and how quickly oxygen could be depleted in the space. Make sure you’ve got enough exhaust, make sure you’ve got enough makeup air to eliminate and reduce those hazards to building occupants.
Jeremy Barrette: We are going to walk through two recent projects that we’ve done and highlight some of the things that we just talked about and how they were applied to some projects. One project was at Arizona State University, the Bio design Institute Sea Building, is a building that we just completed in 2018, and it’s almost 190,000 square feet.
It’s an interdisciplinary building, so there’s a lot of different types of spaces, some unique ones and some generic ones. The university wanted this to be what they called a workhorse building for them. It’s efficient space for the researchers in their offices in very little public space.
It was designed initially as generic lab plans, and then as we went through the design, the university assigned researchers and we redesigned their spaces to align with their specific needs. Most of that was fit out when the building was done, and then a few were done subsequent to the building opening: Houses, three different schools, the College of Liberal Arts and Sciences, the School of Engineering and the Bio design Institute.
The first floor is high bay labs. The second floor was a dense chemistry floor, which has high fume hood usage, high exhaust and high air change rates. Levels three through five were open, flexible labs, they could be for biology, it could be for some engineering, some clean space, light chemical use. Then the basement is very specific. It’s dedicated to the compact X-ray Free Electron Laser Program, and we’ll talk about that in a little bit.
But they also wanted the building to be very, very efficient and we did achieve that. The building was certified lead platinum. Our equipment is generally accumulated in a basement mechanical room in a penthouse with the exhaust on the roof as well.
This was an interesting process going through with the architects and the users to understand, again, asking those questions in the design meetings, “OK, what do you need for temperature? What do you need for air change rates? What kind of hazards are we dealing with, so that we could get the design correct?”
The building is all 100% outside air because we are doing hydronic cooling. We do have chilled beams in most of the labs and in the offices. We have redundancy at the air handler and at the exhaust fan.
When we’re working with the researchers, looking at the needs of these spaces, the accelerator vaults, the laser labs and what’s called The Hutcher. It’s where they’re doing the research on certain, either plant or protein crystals to watch certain things happen. They wanted to have very tight temperature and humidity requirements, and the only way that we could do that is to give each of those labs a dedicated air handler.
The lab exhaust rates and the makeup air to that exhaust does come from the central system, and then in these spaces we’re recirculating the rest of the air to hit those targets. From a sustainable design strategy standpoint, the building’s got a double facade for shading. I mentioned we decoupled the ventilation and cooling with active chilled beams. We did high performance fume hoods and low pressure drop duct work design. We’re setting back those air changes in the generic laboratories when they’re not occupied, and enhanced runaround loop energy recovery system.
We also did wind modeling on the exhaust as to inform what velocity of airflow we needed for the exhaust and help keep our fan energy as low as we could. Free cooling for our process loop and full LED lighting. It’s a broad spectrum of strategies that we used in this building to get that energy performance where we wanted it.
Fortier: Argonne National Laboratory a national lab for the Department of Energy’s office of science. It’s located just outside of Chicago. The new Materials Design Laboratory is a facility that has been in operation for about two years. Here in the last year, it has won several awards from ASHRAE for safety, and it’s a facility that has a lot of the diversity in terms of laboratory types that we’ve been talking about.
Their mission is obviously material science related. Everything from discovery of new materials to synthesis and characterization of new materials. The facility was custom designed to really be directed around eight very specific users that were going into the facility. At the same time, knowing that scientific research is not in perpetuity from a funding standpoint. We also had to take the approach that in some period down the road, probably a couple of years, many of these users may be switching out and coming in with new users, so the flexibility of the systems was very important.
The general footprint of the facility is about 115,000 square feet with four floors of active laboratory use. There was a half partial basement below the ground floor level that housed most of the waterside equipment. Then there was a two-story penthouse above the third floor that the house all the air side systems. Ground floor was driven by a lot of vibration sensitive facility and user needs. The third floor was an entirety of a radioactive suite. So whole bunch of different diverse user types, but there were certainly similarities between them that we were able to apply to design.
There are a couple of different types of spaces there. We had computational labs, we had chemical and biological labs. I mentioned the radiological suite, the ground floor labs that were not above the basement. The ground floor labs that were slab and grayed were for cryogenics laboratories. Oxygen depletion hazards can be a concern.
The facility met and exceeded all the needs that Argonne had. The radiological suite there was probably one of the more unique spaces in the facility, especially given that it was elevated in the building up on the third floor. During construction, there’s dedicated exhaust systems for this floor, HEPA filtration, super high level of quality control required not only during the design, but also during the construction process.
Once the building was built and before occupancy, we actually did a water flood test and they discharged a whole bunch of water out of the floor and made sure that there was no leaking to the second floor below, and that all the water was captured and contained into the plumbing system and directed all the way down to the basement level where we had radiation waste collection tanks, so that water could be tested for radiological materials before it was discharged to the sanitary sewer system. Lots of thought and consideration to doing this type of radiological suite at an elevated level in a safe manner.
With the nature of the facility, redundancy was extremely important. This was a facility that operates 24/7, 365. It never shuts down, so redundancy on the unit on the electrical side was very important. Given the footprint of the facility and where it was on-site, we were limited in terms of how much mechanical space in a horizontal plane we had, which is how we ended up with a two-story penthouse, and trying to get large air handling units in, was causing some concerns.
What we ended up landing on from a design standpoint, was an air handling unit that could function in normal operating conditions at very low velocities; 330 feet per minute through the air handling unit, which was a huge energy saving measure, which helped us with our sustainability goals. But if we did lose an air handling unit, there was three of them designed at 40,000 cfm, the other two air handling units could ramp up to more conventional cooling coil speeds, which at that short period of time used a little bit extra energy but allowed both air handling units that were remaining, to really serve the entire airflow needs of the facility. We could lose an entire air handling unit, still have complete capacity for the facility.
Then on the other side of that was the electrical system, which being a 24/7, 365 facility and being in a Department of Energy national lab, there are very stringent safety requirements that that DOE has; amongst those, you cannot operate on operating equipment. Things like electrical branch panels, things like motors in the air streams, really can’t be operated on without being shut down. In a conventional system design, where we have an emergency generator backing up the system, it’s great in the loss of power, your system continues to operate, but there’s really no way to shut down that panel. There’s no way to get access to a motor without shutting down the entire air handling unit, which is something we were trying to avoid.
What we ended up doing on the electrical side design was splitting those systems. In an individual air handling unit where we had six motors, three were served from one panel on normal power, three were served from a panel on emergency power and then we were able to shut down half of the air handling unit at a time. The owner could do maintenance on the motor, could do maintenance on a panel, while the other half of the air handler worked. There was a partition through the center of the air handling unit, which kept the air stream separate, and really allowed the owner to operate on the system equipment without shutting it down.