IN THE WINTER, it’s a challenge to protect our worshipers from airborne illness while also keeping them warm enough, and while minimizing water damage to our facilities from rainfall. Fortunately, given the relatively temperate climate in Venice, we face this challenge only a few months of the year. Yet during those months, the situation requires active management.
The HVAC control interface via the internet
(As usual, click/tap on an image to enlarge it.)
Each week during cold weather, the trade-offs need to be weighed. Factors include predictions for the outdoor temperature, the wind velocity and direction, the amount of rainfall — and how prevalent and how severe the covid-19, flu, and RSV infections are locally.
Below the jump, this post discusses the challenges and trade-offs. It suggests some management guidelines, based on my experience last winter.
Summary: Management Guidelines
- As a matter of policy, our goal is to make it safe for (vulnerable) people to be around others who are singing.
- Manage expectations; be forthright about the fact that our sanctuary’s heating system is not powerful enough to fully handle the demand on cold and/or rainy winter days while airborne illness is of concern.
- Caution prospective attendees in advance; ask them to bundle up.
- We rely upon natural ventilation to reduce the risk of transmitted disease, because we cannot practically provide filtration.
- In the morning before services begin, keep the doors and windows closed as long as possible, so that the surfaces can be warmed up by the heating system.
- Cover the window openings to the mezzanine with plastic sheeting (or something more permanent) during the winter.
The role of singing
When people are singing, they exude about six times as many aerosol particles (which potentially contain viruses) as when they talk normally. This means that Mishkon’s sanctuary can more easily become a hot spot for disease transmission than, say, an office building or a concert hall. In other words, Mishkon arguably needs to be stricter than many other venues, in attending to the risk of airborne disease transmission.
A limited heating capacity
Our large sanctuary’s ability to deliver warmth on a cold morning is limited by two factors: the room design, and the capacity of the heating system. As you know, the room has a high arched ceiling, in order to create an atmosphere of expansiveness. But this means that warm air (as it rises) tends to collect far above the heads of worshipers, where it does little good.
To send warmed air into the sanctuary, the original heating system used an enormous blower (roughly 6 feet in diameter), which is still housed on the roof, along with very large ducts and registers. Unfortunately, that system wore out long ago.
The replacement HVAC unit has fortunately provided us with air conditioning, which was lacking previously. Yet its blower is strong enough, and its ducts and registers are big enough, to send the conditioned air into the front half of the room only. Given practical budget constraints, was the optimal and cost-effective choice.
Good ventilation capacity
Happily, our sanctuary is quite able to deliver fresh air. Keeping doors open for cross-ventilation is a key strategy. This measure not only provides fresh air at the height where people are breathing, but also it takes advantage of the prevailing breezes to circulate the air indoors.
Opening the stained-glass windows (selectively and gently) is the second means of providing good ventilation.
(Another downside of opening doors and windows is that it speeds up the corrosion of indoor materials by the salty ocean air.)
Air filtration units on the bimah
As a matter of course, the 3 black Coway units on the bimah are turned on their low (quiet) setting during services. (Jeff G. usually attends to this.) These units, which contain HEPA filters, significantly reduce the risk of airborne disease transmission for people who are on the bimah. This filtration is independent of everything else that I am discussing in this post; I mention it only for completeness.
Case study of successful management
This past Shabbat (1-13-24), the arrangements seemed to work out well. We faced a double whammy of a “very high” level of reported local flu-like activity (which includes non-flu illnesses such as covid-19), combined with the arrival of cold arctic air.
Providing good ventilation thus meant seriously reducing our thermal comfort. In advance, it appeared that we could either be healthful or warm, but not both.
Apprised of this situation, our president consulted our medical team in advance. Together they produced the following announcement, which appeared in the weekly email newsletter:
Covid Alert
L.A. County is now in the “medium” COVID-19 hospitalization category outlined by the CDC. Those at high risk of getting very sick or those in contact with someone at high risk should wear a high-quality mask when indoors in public, the CDC says.
In addition, this weekend, it’s supposed to be cold. Unfortunately, opening windows to provide ventilation will make it impossible to keep the sanctuary comfortably warm. But we will be opting for ventilation that makes it safe for (vulnerable) people to be around others who are singing. Therefore, please bundle up - and do consider masking.
That was an important message. Consequently, most people who showed up were mentally prepared to be a little on the cold side, compared to usual indoors conditions. (Managing expectations is one key to success.)
To heat the room, we relied upon the automatic thermostat to start the burners and blower well in advance. When the system started up, it was about 43°F outside and 57°F inside (on the bimah).
We kept the doors and windows closed as long as possible — until 9:20am — so that the surfaces (walls, seats, and floor) would have the opportunity to warm up after the overnight chill. (In a Venice winter, your thermal comfort is more a function of the temperature of nearby surfaces than the air. Recall how warm you can feel when sitting by an outdoor fireplace even if the air is cold.)
By 9:20am, it was about 66°F inside (on the bimah).
During the services, the windows in the front half of the room were kept open — that is, the front 3 bays on the south side, and the frontmost bay on the north side. Meanwhile, one door (of each double-door set) was kept open on each side of the bimah, and on each side at the back of the room, and opening out onto the Main Street entrance.
The heaters ran throughout the services. By noon, it was about 68°F inside (on the bimah), while the outside air temperature was in the high 50s. About 40–50 people were in attendance; everyone seemed comfortable enough.
After services, the opened windows were closed, while the backmost window (at the seating area) was opened during the Kiddush period. And the 3 DIY air filtration units in that area were turned on to their proper (low) setting, with each fan pointed away from seated individuals.
The impact of rain
Next Shabbat (1-20-24), we will be facing something of a triple whammy, in that rain showers are predicted for the morning, with the breeze blowing straight at the south wall. Such conditions make opening windows less desirable. Meanwhile, the amount of airborne illness is reportedly continuing to increase. Fortunately, the low temperature is predicted to be 55°, which is much less cold than this past weekend.
I would recommend opening the front 3 south windows only an inch or two, while opening both of the north windows. Otherwise, follow the same practices as last Shabbat.
Role of the mezzanine
The mezzanine plays a greater role in thermal comfort (and utility expenses) than you may realize. After the heater has been on for an hour or so, the mezzanine gets very warm, like 80–85°. Warm air rises and stratifies near the ceiling; and the three window-like openings between the sanctuary and the mezzanine are more than enough to let in that hot air. That’s why last winter I stapled plastic sheeting over those window openings.
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| Window openings covered by translucent plastic sheeting |
In the meantime, however, somebody removed that plastic sheeting, presumably because they thought it was unsightly. (I had heard such complaints.)
That’s not a good thing during the winter, however. When we are heating the unoccupied mezzanine, not only does it reduce thermal comfort in the sanctuary and drive up our utility bills for no good reason, but also it prematurely ages the archival materials that are stored up there.
Therefore the window openings should be covered again with plastic sheeting (or something more permanent), as soon as possible.
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