THERE’S A LOT of room for improvement in the HVAC system of our school/office building. Thermal-comfort levels are good but not great. Our hospital-grade filter is reducing the risk of airborne disease, but it is taxing the air-supply blower. Running more than 45 hours per week, this HVAC system is much more heavily used than the one in the sanctuary. That’s why in July, when a preschool parent expressed interest in funding a system upgrade, it became my personal highest-priority new project for Mishkon. (This one is moving slowly, however, because I’m still heavily involved in old projects.)
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| A return-air register for mounting in a door (As usual, click/tap on an image to enlarge it.) |
Below the jump, I discuss the prospects for improvement. This work would be done in late December, during the preschool break.…
There are two complementary aspects to this project: improving the air flow throughout the building, and installing an ultraviolet (UV) disinfecting unit in the main air-supply duct. Let’s discuss each one, in turn.
Improving the air flow throughout the building
I have written elsewhere about the air flow problem. As you may recall, the building’s central air system works properly only when the hallways doors are left ajar. Thus I have asked the staff that whenever they lock up the building at the end of the day, they leave all interior doors ajar by default. (That way, when the system starts up in the morning, there will be good initial return air flow to the central unit.) But that requires intentional effort, and it still leaves comfort problems during the day.
The solution is to install return air pathways in the doors that connect to the hallway. These vents would enable purified air to flow freely through the building, while also reducing overheating, overcooling, and stuffiness in individual rooms.
Product literature can be found here, and an ordering page here. These vents—which fit into the bottom of a door—include baffles that block light and sound transmission, while allowing air to flow.
The idea is to order a dozen of these vents ($33 each) and hire a door contractor to install them.
Installing a disinfecting unit in the air supply
This is also known as a dedicated air scrubber/cleaner; it is a separate device within the HVAC circuit. Last month, our HVAC service vendor (Acme) made a scheduled on-site visit. Upon my asking how best to reduce the transmission of airborne diseases, the service technician recommended that we install not only door vents but also a residential-style APCO air purifier unit.
It uses a 49-watt UV-C light to sterilize the air in the supply duct. It would be located in the hallway closet, just above the mechanical blower.
Aside from the installation cost, I estimate ongoing costs of about 25¢/day for electricity, plus $126 every 2 years for a replacement lamp. The unit itself has a lifetime warranty.
Based upon the above information, this product seems to be appropriate and well-designed. It is one of several similar products on the market.
What about wildfire smoke?
My intention is to have available a hospital-grade MERV-13 air filter (which we have been using since last year) for temporary installation during a nearby wildfire. See here for an endorsement of this approach. Although it taxes the blower motor, the impact is minimal when used for only a week or so, on occasion.
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