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Comment by teh_klev | Hacker News Reader

I'd have to question what "near-zero" actually means. I don't doubt that outside the humidity is super low, but inside I have my doubts.

Super low humidity increases the risk of ESD which wouldn't be fantastic for any electronics.

You'd need to walk around with a grounding strap all day otherwise you'll be zapping every bit of metal you encounter. I worked in a newly built data centre where the air conditioning (not the chillers) wasn't tuned quite right and the humidity dropped so low that we were being zapped left right and centre. So I'd love to see the actual figure they're using as "near-zero".

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Among other factors: humidity, even at modest levels, means frost and ice accumulation in any spaces with a thermal gradient.

Given that there's a roughly 150F / 85C temperature differential from the inside (assuming ~70F / 20C interior temperature, and -70F / -55C exterior), and that it never thaws, this means frost/ice accumulation is probably a major structural hazard. Even if it was possible to humidify interior spaces, it might be avoided for that reason.

(I'm of course speculating, though based on discussion of PassivHaus designs in Fairbanks Alaska and the attention paid to moisture, vapour barriers, and frost accumulation, as well as an earlier article I believe linked to HN showing the cold food storage at ASSPS which included massive amounts of accumulated frost, and that I suspect just from moisture contributed by the breathing of occupants / workers within the cold (ambient) storage structure.)

I talked about this with an architect friend, who also mentioned that at-scale humidification is difficult, expensive, and prone to molding. In thinking about air exchange, it seems like they would have to desiccate the outgoing air and shift the moisture to incoming air, which would have to be a challenge.

Interesting.

I've heard of heat recovery on air exchange, but never humidity recovery.

I'm not sure to what degree water is readily available at ASSPS (yes, there's snow all around, but it's cold, and actual precipitation is low), but humidifying air is ... reasonably low-cost, modulo thermal budget for melting snow/ice in the first place.

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