Many older buildings do not have modern HVAC systems that incorporate mechanical ventilation. Some facilities may be heating only, some may have fan-coil units or console units with no means of connecting to outside air. The problem is that most institutions can’t afford to allow those spaces to go empty for the upcoming fall term. Right now, that space is needed more than ever to allow classes to socially distance. Most Universities and Colleges are doing some form of class size reduction, longer days to spread out occupancy or other strategies that require the use of as many spaces as possible to spread out occupants. The question is whether or not those spaces can and should be used safely.
Several studies have pointed out that acute outbreaks have occurred where occupants spend extended periods of time, in close proximity, with inadequate ventilation. While facilities personnel can accommodate the timespan and proximity, if there is no means of mechanical ventilation, what happens then?
Fully enclosed spaces without mechanical ventilation should be avoided for permanent occupancy during the pandemic, that much is clear. However, spaces with at least 4% operable window area meet the intent of ASHRAE 62, the standard for minimum ventilation rates. The standard goes on to say spaces adjacent to the exterior space can be included in that area if the opening between the two spaces equals 8% of the operable window area. Obviously, this is only when the windows are open, which may be a challenge in early fall and as you approach winter. There are ways that future facilities can be built to utilize natural ventilation when conditions permit, and if you want to read some riveting material on how to approach those designs, you can read through 40 pages of highly technical application here.
There are other considerations as well. If the outside air conditions are not optimal as far as temperature and humidity are concerned, people may start to remove masks due to sweating. We have to be cognizant of the fact Americans are not used to wearing face coverings, and any excuse to remove them would likely be taken.
Finally, people moving en masse are excellent fans. So class changes result in a double edged sword. People moving into a building in a group bring in a large amount of fresh air with them, doing an excellent job of ventilating lobbies and corridors which may be stagnant in the facilities described above. Those same people are also bringing room air out into the corridor when leaving classes, so there may be an argument to reduce occupancy in common areas, which would promote people to move in and out of buildings, providing their own ventilation.
While there are still no clear answers given the short duration of time between the outbreak and our current dilemma, pragmatic approaches and common sense when it comes to space utilization and ventilation can still be applied. If a space has no means of ventilation, it’s probably best left unoccupied.
Contributor: Stephen Oskin, PE, LEED AP, Director of Mechanical Engineering at Barton Associates.
