Questions to Ask: Fume Hood Research Pt. 5

Part five, the final part of a series highlighting recent fume hood research by Andrea Love, Ron Blanchard, Michael Mandeville and Luke Laverty exploring the potential for energy savings through a better understanding of minimum fume hood flow rates and diversity factors for high-intensity labs.

Though fume hoods are one of the main energy users in a laboratory, their role as a vital safety feature is unlikely to change. Working together with owners, users, engineers and manufacturers, we can explore energy reduction options and strategies to improve the energy efficiency of our laboratory projects. Below are some of the key questions to ask during the design process:

1. Do you really need a fume hood?
Reducing the number of fume hoods in a building can majorly impact energy use. As well, a ducted fume hood might not always be the only or best option. Ask users and owners whether a fume hood is required or if an energy conserving alternative option, such as a capture hood, ventilated storage cabinet or exhaust snorkel, is acceptable.

2. How low can you go?
In addition to reducing fume hood counts, reducing fume hood face velocity provides substantial energy and cost savings. Ask owners to review their fume hood exhaust guidelines while educating them on the effectivenes of lower face velocities in maintaining adequate containment. You should also ask fume hood manufacturers about their ASHRAE 110 test data while researching if there are other models that may provide a more energy efficient solution.

3. Can you shut the sash?
Though not always strictly adhered to, standard user protocol is for the fume hood sash to be closed when not in use. In addition to safety benefits, this action can greatly reduce the fume hood’s energy use. Ask owners to consider including fume hood features such as automated sash closers to encourage this practice. Additionally, ask engineers to study their setback calculations and reduce closed sash exhaust volumes towards the low end of the ANSI/AIHA Z9.5 range.

4. What’s our project’s diversity factor?
Air handling units are sized per the maximum amount of air they need to pull in, a variable which is directly impacted by its diversity factor. Determining the project’s diversity factor; the estimated percentage of a building’s total peak air needed for the fume hoods at one time, accounting for those closed and partially-open, could reduce your AHU size(s) and save your project a substantial amount of money. Work with the engineers to discuss the cost savings and future lab flexibility limitations with the owner, including researchers and EH&S, to fully understand this decision.

5. How do the fume hoods integrate with the whole building’s energy strategy?
Fume hoods are part of a larger building energy scheme beyond their own power and air needs. Sometimes fume hoods act as part of a room’s general air change exhaust (ex. one or two hoods in an open lab). They can also be a part of a cascading strategy that requires air to be pulled in from another space. Work with the engineers to consider the whole building as an integrated energy system and how fume hoods play a part in the overall supply and exhaust strategies.

Related Links:
Low Flow is the New Norm: Part 1
How Low can You Go?: Part 2
Shut the Sash: Part 3
Diversity Factors: Part 4