Adding Fans in the Sanctuary

WHEN OUR SANCTUARY IS RELATIVELY FULL, such as on the High Holy Days, the need for ventilation is higher — especially during an airborne pandemic. Arguably this is when it makes sense to re-install electric fans in the window openings. 

In this post, I recommend a particular configuration for those fans, while offering two caveats for their operation.

NOTE:  Adding fans in the sanctuary is one of three parallel avenues that are being explored to reduce the risk of airborne infection in the sanctuary, for the sake of public health during the pandemic. The other two avenues are: air conditioning filtration, and placing air purifiers on the bimah.

Executive Summary

RECOMMENDATION:  Re-install the 7 fans that have been stashed in the Mezzanine — pointing 4 to blow inward, and 3 to blow outward. 

Run them at low speed, as being the optimum level to balance ventilation with low noise control, as befits a worshipful setting. 

During installation, vibration of the window frame should be addressed so as to avoid destabilizing the leaded-glass windows.

Our Fan Club

Just inside the entrance to the Mezzanine is a stash of 7 box fans (6 of them in boxes). They are sized at 14" in diameter. (The model is discontinued.) At low speed they are rated at 1200 cubic feet per minute, at a noise level of 46 dB — which is said to be at the boundary between “quiet” and “moderate noise,” or somewhere in between a babbling brook and a refrigerator. 

They are not made for outdoor use, so it’s not a surprise that their back cages now look rather rusty — after presumed long exposure to moist, salty air and perhaps to rain.

The bungee cord at the top is used to secure the fan to the window frame.

VIBRATION RISK.   According to Ruben, the fans do not create appreciable vibration. However, rotating machinery normally does create some vibration, because it is not designed and manufactured to be perfectly aligned and symmetrical. Therefore at least minor shaking of the metal frame (to which the fan is secured) seems inevitable; and such vibration would predictably be magnified at the far (cantilevered) end of an open window panel. 

Consequently, I believe there is a very real risk of adversely affecting the leaded-glass windows—especially the sagging ones and the ones with crumbling putty. The safe thing to do would be to mechanically isolate the fan from the frame, by inserting a piece of neoprene rubber beneath the fan, and another in between the fan and the vertical frame piece.

Suggested Configuration

I suggest that we point 4 of the fans to blow inward, and 3 to blow outward. That should keep the air circulating nicely, without creating drafts at the doorways. The exhaust should be directed toward the south side, because people do live near the north windows (in a 2nd-floor apartment), whereas nobody outside is near the south windows.

(As usual, click/tap on an image to enlarge it.)

Public Health Notice

A quote worth taking into account: 

Higher ventilation … rates more rapidly remove particles from indoor air, thereby reducing the intensity of exposure and duration that respiratory aerosols stay aloft inside a room.…

[However,] improving indoor air ventilation … only accounts for far-field (ie, beyond 6 feet) aerosol transmission and does not significantly influence close contact transmission. Wearing masks is still important indoors for source control and for close contact with individuals even when high air exchange rates are achieved.

—Joseph G. Allen and Andrew M. Ibrahim, “Indoor Air Changes and Potential Implications for SARS-CoV-2 Transmission,” JAMA Insights; in Journal of the American Medical Association 325(20) [April 16, 2021]: 2112–13. doi:10.1001/jama.2021.5053