Your questions answered about HVAC: Labs and research facilities
After the Aug. 11, 2022, webcast, the presenters answered several questions left open during the presentation
- Engineers may be asked to design several different types of labs, including radiological, biological clinical, animal or computational.
- There are several ways to design HVAC systems within labs. Some designs focus on energy efficiency and sustainability.
Labs and research facilities house sensitive equipment and must maintain very rigid standards. Heating, ventilation and air conditioning systems in particular require careful planning and design. Most labs require the HVAC system to be fully exhausted, requiring high levels of outside air. This was discussed at the Aug. 11, 2022, webcast “HVAC: Labs and research facilities.”
Topics such as air change rates, pressure relationships, relative humidity, low-temperature design, energy savings and cross-contamination were covered.
Many labs require specialized, unique systems such as fume hoods, purge systems and containment solutions. Questions were answered about these topics in the discussion and below.
Subject matter experts:
- Jeremy Barrette, PE, EDAC, HFDP, Principal, Affiliated Engineers Inc., Phoenix
- Brandon Fortier, PE, LEED AP, National Leader Science & Technology/Principal, IMEG Corp., Naperville, Illinois
Do engineering labs require a lot of snorkels?
Jeremy Barrette: It may depend on what specifically is occurring within. Soldering stations are one example that would require snorkels.
Are the animal rooms return air with a specific amount of fresh air or is 100% outside air a typical application?
Jeremy Barrette: Animal spaces typically require 100% exhaust and 100% makeup air is usually important to avoid nuisance odors, etc. if office air where to be transferred in.
ASHRAE defines lab air changes per hour/ventilation air as “outside air.” How can labs supply air systems be mixed air? Even those named dedicated outdoor air system?
Jeremy Barrette: Labs typically require 100% exhaust. The makeup air does not always need to be 100% fresh but can be air returned from non-lab spaces in some cases.
Does cleanroom ACH per ISO-14644 account for the heat load removal from the rooms? If I need to calculate the cubic feet per minute for the room, do I need to do a load calculation as I do in any typical building room or I can just use the ACH x ROOM VOLUME/60 equation?
Jeremy Barrette: When higher air changes are used in cleanrooms, the supply air temperature may approach the space temperature to avoid high reheat. The space cooling needs will come into play in determining the supply air temp.
How about cross contamination from the office space into bio labs?
Jeremy Barrette: If cross-contamination is of concern, an additional layer of protection of anterooms may be required to cascade pressurization.
Can transfer air affect the cleanliness and operational requirements of a particular lab?
Jeremy Barrette: Yes, it can. If that is a concern, the source of transfer air may need to be reviewed.
How accurate is wind dispersion analysis in determining recirculation of exhaust air back into outside air intakes?
Jeremy Barrette: That is a question better posed to a wind modeling firm.
What type of conflicts arise when generic labs are designed? Is a modular or flexible approach taken with HVAC equipment?
Jeremy Barrette: Generic labs need to have its parameters and limitations defined an the client needs to be informed of what can and cannot be accommodated later.
Have you found dehumidification a need in the air handlers for labs? In Oregon/Washington we have found that it has been an increasing need during the shoulder months.
Brandon Fortier: Dehumidification is a need dependent on the geographic region the laboratory is in. The Argonne example I presented is located outside of Chicago which has hot and humid summers so dehumidification was a requirement.
Why not just put individual disconnect switches on each fan motor for the last example as opposed to two different panels?
Brandon Fortier: There was no way to work on the branch panel without turning off all loads on the panel due to Argonne Safety requirements. Separating the loads onto two panels allowed for routine maintenance without turning the air handler off.
Does an energy recovery ventilator typically risk cross contamination?
Brandon Fortier: It depends on the type. Enthalpy wheels absolutely risk cross contamination. Run-around loops do not as the ducts are not physically connected or often times even near each other.
What would you recommend for energy recovery in a prison with an purge/evacuation system (for smoke, pepper spray, etc.)?
Jeremy Barrette: Energy recovery options that do not allow for cross-contamination to supply air.
Which electrical equipment typically requires emergency power, not including those with redundancy concerns?
Brandon Fortier: Emergency lights are frequently placed on a generator and many laboratories will have a supply of emergency power provided for receptacles to be used for Owner equipment.
In optical labs, we typically control the discharge air temperature as our primary temperature control loop. The room temperature is then used as a secondary loop. This maintains stable temperatures near the optical instruments. Are you seeing this?
Jeremy Barrette: In optical labs with tight environmental requirements, we may place a high accuracy sensor immediately adjacent the laser equipment that requires the stability, rather than a wall mounted sensor.
Were the building automation system controls also separated into two halves for the air handling units, or just the motors?
Brandon Fortier: The controllers were not separated onto two controllers, but they were placed on UPS power and the generator.
Can plate heat exchangers be used for sensible only heat recovery from lab exhaust?
Brandon Fortier: Yes, these can be used as they don’t cross contaminate airflows, but the physical size of ductwork in HVAC systems often makes plate heat exchangers a difficult option to implement as opposed to run-around-loops.
What is the trend in how much plug load (watts/square foot) are laboratories being designed for?
Jeremy Barrette: Plug load design assumptions will vary greatly depending on the type of lab. For basic, flexible labs, we may start at 4 W/square feet and discuss with the client from there. Metering existing, comparable labs can be a great way to confirm assumptions.
What’s your opinion on air sampling systems considering that they can help reducing total air changes?
Brandon Fortier: I have used air sampling systems in laboratories but recommend closely coordinating their use with the Owners Industrial hygienist. Commercially available systems do not sample for all types of hazards and may not be appropriate for all applications.