Chemistry Labs: “Top Five” Energy Efficiency Strategies by Building Type
“Chemistry” labs have heavy chemical use and many fumehoods. Their energy use is dominated by the need to heat, cool, and move huge amounts of air, to supply fumehood makeup air demand, ventilated cabinets, and / or specialized processes.
The laboratory fumehood is a safety device designed to protect its user from exposure to hazardous chemicals by maintaining a constant airflow away from the user, and into the fumehood cabinet. To achieve this, fumehoods are connected to the building HVAC exhaust system. The air that enters the cabinet is sucked out of the laboratory, treated by building equipment, then blown up into the atmosphere. Air that exits the laboratory through the fumehood must be replaced (“made up”) by fresh air from outside the building.
As in the biology laboratory, this places a huge energy demand on heating, cooling, and moving air around. In chemistry laboratories with many fumehoods or vented cabinets, the fumehood air demands can far exceed the “Lab Air Change Rate”, resulting in airflows 3-6 times those in a biology lab (3-6 CFM/sf or 18-30 ACH).
This has the effect of turning the lab into a “wind tunnel”, where a constant stream of raw outdoor air is sucked into the building, treated (heated, cooled, humidified, and/or dehumidified), passed “once through” the lab, then exhausted back to the atmosphere. This constant airflow means that air in the building doesn’t stay long enough to lose or gain heat through the building’s exterior walls or windows.
The most effective EEMs for Chemistry Labs are those that target reducing air flows. Of secondary importance are technologies that reuse “waste” heat / cool from the exiting exhaust air. EEMs that decoupling heating / cooling from airflows are almost meaningless, because the air is moving so fast that the air doesn’t have time to pick up heat / cool from chilled beams or radiant sources. Other mechanical and electrical EEMs can be effective, but have negligible impact on total energy usage. EEMs that target the building envelope, such as increased building insulation, reduced glazing %, and triple glazing, are almost meaningless.
Our “TOP FIVE” EEMs for Chemistry Labs are:
- Optimize building program distribution (space planning for energy efficiency).
- Consider planning separate “office zones” that are driven by different AHUs (to allow partial use of recirculated air)
- Plan labs with “fumehood ballrooms” as big as possible relative to # hoods in them:
- Don’t put large numbers of fumehoods close together.
- Don’t put fumehoods in small rooms.
- Consider “stealing” air from surrounding corridors, offices, writeup stations, etc. into the lab to maximize the effective room volume from which the fumehoods draw makeup air.
- Optimize airflow safety device (fumehood) selection
- Reduce number of Fumehoods and other airflow devices as much as possible. If possible, limit capacity for future Fumehoods.
- Use alternative safety devices where safety concerns do not require a true fumehood (Rotovap cabinets, plexiglass capture boxes, snorkels, etc.)
- Use a “filtered” Fumehood instead of a ducted Fumehood, if the research application is appropriate for these devices
- Optimize Fumehood device specifics (ducted fumehoods)
- Install energy efficiency measures, either:
- “Automatic Sash Closers” with vertical rising sash (max efficiency) or
- “Energy Awareness” system with combo sash (backup alternative, less efficient)
- Optimize Fumehood “minimum draw with glass closed”
- WA has found that minimum flow requirements are often a bigger energy demand issue than “face velocity”, though face velocity gets more publicity.
- Recent changes to ANSI / AIHA Z9.5 have reduced fumehood minimum flow requirements significantly, provided that fumehood selection / specification is optimized for good internal cabinet dilution / concentration removal.
- WA uses 250ACH of internal cabinet chamber as a starting point for discussion with the research groups, EHS officers, and fumehood manufacturers.
- Optimize Fumehood “Face Velocity”
- Wilson Architects has found that 70fpm face velocity, with a +/- 10% variation for balancing, is a realistic rule of thumb for low flow (“high efficiency”) fumehoods. Many manufacturers offer fumehoods that meet testing requirements at 60fpm. Some NIH technical papers appear to recommend 80fpm for operation in real-world installations. We have had good success with hoods at 60, at 70, and at 80fpm installed in our laboratories. But, due to the competitive bidding environment, challenging nature of subcontractor installation, and unique configuration / requirements of some labs, we acknowledge that we do not have perfect control over the precise configuration of fumehoods as installed. So we recommend 70fpm.
- WA recommends that clients consider eliminating institutional “face velocity” requirements (ex. 100fpm or 80fpm) in favor of letting the design team optimize velocity to the precise fumehood selection. WA suggests that clients instead require 100% testing of fumehoods “as installed” to a stringent standard, such as the “NIH walk-by test”.
- Optimize Fumehood “minimum draw with glass closed”
- Demand control ventilation
- Via chemical concentration detection (“Aircuity”) in lab spaces
- Unoccupied mode for lab ventilation, including setback for fresh air delivery, temperature stability and setpoint, and humidity stability and setpoint
- Optimize mechanical equipment
- 100%OA system
- Heat Pipe AHU
- Airside Economizer
- Multiple Exhaust Fans / Stacks (at least 3) to maximize exhaust plum turndown options
- Conduct wind study to specifically address options for exhaust plume turndown
- Use central plant resources if available
- High Efficiency Boilers, chillers, cooling towers, etc.
- Optimize building envelope
- <40% glazing
- NOTE: Wall R, thermal bridging, and air tightness don’t matter as much
- High efficiency fluorescent lighting
- Low Ambient / Targeted Task lighting (incl. low Footcandle levels)
- Daylight Dimming
- Vacancy Sensing
“GO BEYOND” STRATEGIES
- Geothermal Heat Pump
- LED Lighting