Tips for good ventilation and thermal comfort in our school building

PICTURE A HALLWAY that’s lined with doorways. You might think that in a proper hallway, all those doors should be closed. A nice and neat look, yes?

Yet that is not how our school building was designed to function! 

This post discusses our building’s characteristics, and how best to work with them.…

Doors must be partly open for good ventilation

Whenever the building’s mechanical heating, ventilating, and air conditioning (HVAC) system is on, the hallway’s doors are supposed to be propped at least partway open.

That’s the only way that the indoor air can circulate and thus be properly filtered, for the sake of minimizing airborne infections. 

How so? In this system, the blower fan pushes the treated (filtered and heated or cooled) air out of the room registers that are up high on the wall that’s nearest the hallway. How does that air then get back to the HVAC equipment, which sits in a closet off the hallway? Through the hallway itself — it serves as the necessary return channel. The furnace and A/C both get their intake air from a hallway grille at floor level. 

This grille at the floor level in the hallway
is the source of the air that gets heated/cooled.

Such a system can work right only if the room doors are propped open somewhat.  

Doors must be partly open for thermal comfort

Likewise this set-up affects the functioning of the thermostat, which is likewise located in the hallway. The air in that hallway gets no heating/cooling at all by the HVAC system unless at least one internal door is open to the hallway. Thus if all the hallway doors are closed, the furnace or A/C will keep on running — because the hallway’s thermostat doesn’t experience any local change in air temperature.

In other words, the building’s various rooms become overheated or overcooled unless one or more hallway doors are slightly ajar. So let me recommend that during the normal HVAC operating hours (8 a.m. to 5 p.m.), the room doors be closed only when necessary to avoid disturbing the planned activities inside that room.

An additional (or alternate) way to ensure that the rooms themselves are comfortable is to set the thermostat so as to keep the hallway at a seasonally uncomfortable temperature. Arrange for the hallway to be uncomfortably cool in winter, and uncomfortably warm in summer. 

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I leave it to the staff to find the right combination of measures that will work best for the operation as a whole.