Once commissioned, fume hoods operate continuously to provide a safe working environment. Fume hoods consume a lot of energy through the operation of the ventilation fan and motor require energy. In addition, the air that is exhausted must be replaced and that air requires conditioning (heating in the winter and cooling in the summer). This energy can be even higher in humid or cold climates. Humidity conditioning is a big energy consumer.
Fume hoods can account for 60% of a lab’s energy consumption.
Shut the Sash
Most modern hoods operate on a “variable air volume” (VAV) system. This means the volume of are being drawn through the hood depends on the size of the opening.
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The sash is the moveable pane at the front of the fume hood
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Always put it in the lowest possible position
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Works best for Variable Air Volume hoods, can reduce exchanged air from 600 m3 to 200 m3 per hour.
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Saves energy by 30%
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Use “Shut the Sash stickers” to remind colleagues
Here’s an example from the University of British Columbia
Harvard has real-time displays of ventilation rates outside of every lab to help lab scientists see their impact (and know when they’ve left the fumehood open).
- Harvard’s Shut the Sash campaign saved $280,000/year
Try an automatic Sash closer
Turn off when not in use
Avoid storing things in the hood. If you don’t store chemicals in the hood, then you can most likely safely turn off your fume hood when not in use. If it can’t be turned off, then at least turned down in the evenings when no one is working. Some fumehoods need to be decomissioned by your institute’s Facility services. They will temporarily shutdown the hood and block it off to prevent unknowing people from accidently using it. Shutting down is reversible, so don’t be afraid to ask. It can save up to $2,500 USD/year.
There is an erroneous belief that flammables must be stored in a fume hood. This is rarely the case. Please check with your safety team.
If chemicals must be stored, please consolidate so that only one fume hoods needs to be left on.
Check your minimum fumehood air change rate.
ANSI Z9.5 standard allows lowering minimum fume hood air changes rates from 375 to 175 if you hae no flammabes.
- Takes some help from building services. Easy for VAV hoods (2 hours of work), a longer for constant air flow hoods, but possible.
Purchasing
- Consider Ductless hoods, depending on your hazards
- Choose a Variable Air Volume (as opposed to Constant Air Volume) hood
- Choose Demand-controlled ventilation system that varies the flow rates according to when hoods are in use
** Can reduce occupied air change rates from 8 to 4 for occupied and 4 to 2 for unoccupied (but will go up to say 16 if hazardous chemicals are being used) - New (last 10 years) efficient fumehoods and HVAC systems usually doesn’t need more than 60feet/min air flow (Low flow hoods).
- Be really careful, often new buildings contractors will put in the cheapest hood possible - probably a very old style one. Get involved early to have input on the hood.
- Have a study done to ensure lower fan volume can safely punch up and away from the lab (costs ~$20,000 per lab building for computer study, $50,000 for wind tunnel study )
- Fumehood replacement payback period is ~6months from energy savings
- In fumehood dominated building, can save up to 50% of your energy bill
Green Your Experiments
Work with your facilities team to reassess the ventilation requirements for your experiments. Is the air change rate suitable for the work that is being done.
In addition, look at using more Green Chemistry. Using fewer harmful solvents and reactions means that the air change rate in the fume hood and lab can be reduced.
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