Bookish Question
I’ve been approached by a retired librarian/author to build a small outbuilding on his property (Northwest Vermont, zone 6) in order to store his books. In searching for ways to save energy on his heating, I’ve tried to keep in mind how turning down the temperature in the 300 sq ft building might effect the longevity of the wall and roof assemblies, as well as the books themselves.
After reading about Ben Bogie’s use of interior sheathing to increase the resilience of the wall and roof assemblies,…
(Interior Sheathing and Exterior Fiber-Board Insulation – GreenBuildingAdvisor; A Resilient Roof Assembly that Can Handle Moisture – YouTube)
…I wondered if there could be a case for using such a system here, where the customer would like to turn down the heat in an outbuilding, while keeping the occupants the books comfortable? (I should not have tried to be cute here, see edit below)
Would keeping the plywood to the interior help to keep it above the dewpoint temperature in this situation (presumably we don’t want it to get too dry)? What would happen to recommendations for humidity as the room temperature dropped (I read in one place that books should be kept at a relative humidity of between 30%-50%) Is this a case where relative humidity could actually be a useful concept?
As excited as I am about the conversion of the Maine paper mill into a Timber HP manufacturer, with hope I can keep his collection from being pulped.
Thanks!
Edited for clarity: I hoped that the customer could use the building for reading/writing during the cold, dry winter months at around 70 degrees, with 35-40% humidity, before turning down the temperature when unoccupied.
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I recommend reading this thread:
https://www.greenbuildingadvisor.com/question/wood-air-and-water-the-interplay-of-temperature-humidity-and-wood-moisture-content
What I hope you take away is that at low temperatures the humidity has to be very low to avoid the risk of mold or rot in wood.
My opinion based on observation is that paper is probably more prone to mold than solid wood.
So you will probably have to condition the interior of this building since it's in such a cold place. The good news is you won't have to ventilate it, nor will you have sources of humidity. So I think if you air seal it well and insulate it well a dehumidifier will probably provide enough heat to keep it at a safe climate.
Wow, thank you, this is really interesting. I wasn't aware of that inverse relationship in moisture holding between air and wood.
Mold won't grow below 50 degrees Fahrenheit. So during the winter in Vermont, just keep the library cool.
I should have been more clear about how I hoped he could use the room. I assume at some times in the winter he will want to read/write in there at a comfortable temperature (say 70 degrees, at 35-40% humidity). Since it's an outbuilding, he would probably need to humidify the room while using it. It sounds like turning the room down to 60 would be worse than turning it down to 50 for mold purposes?
If I had a Panasonic ERV in there, it would probably clear out any humidity he added from a humidifier pretty quickly. At that point my gut says that the books are not going to handle fluctuations in humidity very well, but of course they may not absorb all that much if he doesn't use the room more than, say, 4 hours a day.
reldred79,
I build a she-shed for my wife about five years ago which is entirely lined by bookshelves and holds about 3000 volumes.
It is insulated on the exterior with foam board on all six sides and has a small portable oil filled heater. We keep it at 14C in the winter and boost it up to 20C when she wants to spend time there.
With no regular sources of moisture the RH lags about 5 points below our house, rarely exceeding 50%. The books show no signs of problems, however as DC says, reducing the temperature in the shed makes them more vulnerable. In your case I'd err on the side of caution and use more insulation to offset energy needs, rather than rely on keeping the building colder.
Thanks, and this is the first design I had in mind before I saw Ben's article (Exterior foam, though I'm not sure about a roof assembly yet). Good to know.
https://www.nedcc.org/free-resources/preservation-leaflets/overview
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