The #1 rule for all Professional Engineers – the folks who design, authenticate, and oversee every construction project – is that nothing is more important than the health of the individuals. In the case of buildings, the main relevance for HVAC engineers is to maintain a healthy air quality.
Once a building is constructed, the P.E. is no longer involved. It’s up to the new owners and their maintenance staff to keep the engineered systems functioning as designed.
As an example, consider a classroom at your neighborhood school. That room, by HVAC standards, must be flushed out completely with 100% fresh, outside air at least 5-6 times per hour. This removes the carbon dioxide and replaces it with fresh oxygen. In a hot and humid climate, dehumidifying and cooling down that much outside air in the summer is very expensive. Dehumidification costs at least as much as cooling.
The outside air volume delivered to the central air handler system is typically controlled by a single damper. Closing that damper, even partway, can save a bundle on the utility bills. Given that school districts are under constant fiscal straits, the temptation to close that damper (or to not repair an inoperative OA damper) is tangible. There are no laws to monitor that design outside air changes per hour; no required oversight or annual inspections of HVAC systems; no penalties for neglect. Nor can the P.E. of record be held liable because once the facility is commissioned and turned over to the owners, said responsibility is terminated.
What happens if a classroom gets no outside air? The carbon dioxide level builds up and oxygen becomes depleted: you get carbon dioxide toxicity and oxygen deprivation. The latter is evidenced in “altitude sickness,” when you go to a high altitude. The symptoms begin with dizziness and headache, then poor attention span, lack of affect, and eventually psychosis. These are the exact same symptoms as Attention Deficit Disorder. Add carbon dioxide toxicity, and you’ve got double the problem.
Every enclosed, occupied space has the same need for fresh air. The higher the occupancy and activity level, the more outside air exchanges that are needed. In my book Retrofitting for Energy Conservation, I repeated dozens of times: you can never, ever sacrifice the health of the occupants in order to save energy.
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Excerpted from Going Green, available as an eBook at this list of eBook retailers online.