Net Zero Laboratory Buildings Part 2: Applying Net Zero to Labs | Space Conditioning and Fume Hoods

By: Matthew Fickett AIA, CPHC, LEED
Principal

What does this mean for labs?

In Part 1 of this series, we discussed what makes a building Net Zero, why a Net Zero building must be all-electric, and a key piece of technology which allows efficient, cost-effective electric space conditioning: the heat pump.  But what about laboratory buildings?  Don’t they have all kinds of special needs?

Space conditioning, the lab version

In fact, the biggest energy draw in a lab building is space conditioning, just like it is in most buildings.  The difference is that in a lab building, it is often five or ten times more than in other building types!  The reason is rooted in safety: many science processes are dangerous to people, and to protect the scientists from their work, the air in the room is completely replaced every few minutes (commonly, six times per hour).  Even more significantly, much of the work in a lab is done inside fume hoods, which pull in air from the lab and may exhaust it directly outside. This keeps scientists in the lab safe but requires the building to spend enormous amounts of energy conditioning fresh air, only to immediately throw it away.

The first step is simple: reduce the number of fume hoods (by reducing the number of hoods just used for storage and by encouraging sharing of hoods where possible) and then reduce the amount of air that goes through them.  Modern hoods are far more air-efficient than older ones, while being safer than ever.  Better engineered airflow, automatically closing sashes, variable air volume (VAV) controls, and occupancy sensors all work together to cut air use by half or more.

The second step is slightly more complicated: capture heat from outgoing exhaust air.  This is already common in ordinary exhaust from, say, office space.  There are a variety of technologies, but the principle of them all is the same: capture the warmth out of the exhaust and put it back into incoming air, before the building heats the air up.  (Or, of course, the reverse in the summer.)  This is not commonly applied to lab exhaust, but there’s no safety reason which would prevent it.

The last step is the most difficult: get rid of the fume hood exhaust altogether.  Hoods without exhaust, called “ductless” or “recirculating” fume hoods, just run the exhaust through very high-grade filters before releasing it back into the lab.  This may sound scary, but think about it: if the lab exhaust is dangerous to breathe, should we be releasing it out into the world anyway? It would be far better to treat it until it is safe, and once that’s done, you might as well get the benefit of keeping the heat energy inside the building.

Can we really do science in filtered fume hoods?

A filter for a fume hood is, of course, more complicated than your average air filter.  The filter set has to be selected for the chemicals or processes to be used in the hood.  It’s easy to imagine a strong acid used with the wrong filter which just melts the filter.  This makes it sound like a daunting prospect, but it’s not as difficult as it sounds to get it right.

Most lab processes are fairly well known in advance.  There are already many rules about what chemicals can or can’t be put down the drain, or how hazardous waste must be disposed of, or what tools and surfaces are compatible with which work.  It’s actually quite unusual that we say “go ahead, put anything you like into the atmosphere, don’t worry about it!”  Instead, a lab can be designed where certain hoods are used for certain tasks.

For the tasks you really can’t know in advance, like some R&D processes, one or two fume hoods could still exhaust to the outside.  It would be better to get rid of them completely, but if 90% of the hoods in the building can be filtered, that’s still a great improvement.

What else?

That’s great for fume hoods, but there’s so much else to a lab! What does going all-electric, Net Zero do to the rest of the project?  We’ll discuss that in Part 3 of this series.