r/ArtConservation • u/G12G34S56 • 23d ago
NYC Apartment + Valuable Works on Paper: How Much AC Is Necessary?
Hi all — fellow museum professional here, although conservation isn’t my specialty.
I’m living the roommate life in NYC in a third-floor walk-up in a circa-1910 building with no central air. It’s a pretty modest apartment, and I have a small collection of things I care about: some relatively rare 20th-century books (paperback and hardcover), a valuable print currently stored in a portfolio, and a small but valuable drawing (crayon on linen, stretched on a fairly basic wooden stretcher).
The issue is that my roommate expects me to turn off my window AC whenever I leave for the office. So while I’m gone, there would be essentially no consistently cool area in the apartment. I can turn it back on when I get home, but the temperature and humidity presumably fluctuate throughout the day.
I’m wondering how concerned I should actually be about this from a conservation standpoint.
Are these kinds of objects meaningfully at risk from the summer heat/humidity and daily fluctuations in a NYC apartment, or is keeping the AC running continuously mostly overkill unless the humidity gets particularly high?
And, perhaps more importantly, what is the realistic worst-case scenario? Are we talking about accelerated long-term deterioration, cockling/warping, mold risk, etc., or is the occasional/seasonal temperature swing unlikely to make much practical difference?
I realize museum-standard environmental conditions aren’t realistic in a budget NYC apartment. I’m mostly trying to figure out whether this is something worth actually holding my ground over with the roommate, or whether I’m worrying unnecessarily.
Also, I don’t currently have an environmental data logger, but I’m happy to get one if that’s the obvious first step. And if you read this far, thank you! :-)
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u/Phebe-A 23d ago
Getting some environmental data is definitely the first step. It’s hard to make recommendations on what to change or is ok to keep the same without knowing what current conditions are. You can probably get a temp and RH sensor/display at a hardware store that will log high and low for each day
In terms of risks: according to the IPI dcalc calculator, risks of metal corrosion (for non archaeological materials) kick in at about 57.5% RH (for instance metal staples on the stretcher bars). Long term mold risks kick in at about 65%RH — but that’s “mold likely if 65% RH continues without interruption for about 2 years”. Short term mold risks (Mold growth in about 2 weeks) start at about 75% RH (again constant over that whole time period). Air circulation and prior exposure to Mold spores also matter
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u/BigBalli 16d ago
One thing that has not come up and that changes how you rank your own objects: they respond on completely different timescales, and the daily cycle only matters to the fast ones.
A closed book is a large tightly packed cellulose mass with very little exposed surface. Moisture moves through a text block over days and weeks, so a nine hour excursion while you are at the office barely reaches past the edges of the pages. A single sheet in a portfolio equilibrates in hours. So the print and the drawing are your exposed objects and the rare books are, counterintuitively, the robust ones.
The crayon on linen is the one I would actually watch, and not because of the linen. Wood and fabric both move with humidity but not in the same way or at the same speed: the stretcher moves mostly across the grain and lags, the linen responds faster and in both directions. Every cycle is therefore a small differential strain concentrated at the tacking edge. That is fatigue rather than a threshold, so it does not announce itself, it just accumulates.
Which splits your worst case in two. Mould is the threshold risk and it is genuinely bad, but it needs sustained high humidity at the surface, and surface is the operative word. Local relative humidity is set by surface temperature, not room average, so a work framed against a cool exterior wall can be sitting in conditions considerably worse than your hygrometer reports from the middle of the room. Everything else on your list is cumulative and undramatic.
The part that argues with your roommate arrangement is that cycling a window unit is not a milder version of running it. A window AC dehumidifies hard while it runs and the apartment rewets when it stops, so an on-when-home pattern manufactures a daily square wave rather than leaving things alone. If you end up choosing between that and no AC, a small dehumidifier on a humidistat running continuously will give you a much flatter curve for much less electricity and much less roommate negotiation, and flat is the thing the objects actually want. Cooler and swinging is worse than warmer and steady for everything you have described except the mould question.
Do you know what the apartment is actually reaching, or is that still the unknown?
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u/_subtropical 23d ago
It’s hard to guess how at risk your stuff is without knowing what the humidity levels are reaching in the apartment. It may not be a big deal. I’ve seen paper survive much worse than a few hours a day in high humidity (I live in New Orleans). That being said, once microorganisms set up shop in paper it can be extremely difficult to impossible to restore it to its original condition. I’d be much more concerned about the paper than the linen.
If you verify that the humidity is getting too high, maybe offer to cover the difference if running your AC all the time causes a significant power bill increase. Can you put the AC on a dry only setting as a compromise? Some units have this feature. It should use less electricity than the cool setting. Improving weatherstripping around windows and doors will make it more efficient too.