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Root Cellar Venting and Wall Material Questions

 
Steve Sherman
Posts: 7
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We have a small room (6'x8') which is in the NW corner of our barn, at the basement level. Two walls are concrete foundation in direct earth contact (with moisture barrier on the outside), the other two are insulate 2x6 stud construction. Ceiling is insulated 2x joist construction. We have been using this room to store root crops for a few years before it was finished, and it has worked somewhat. There were issues of it getting below freezing when it was very cold out, and it tends to be drier than one would like for storing many root crops. I expect the temp thing to be solved once all the insulation is up. But before I do insulate, I need to run some vents.

I've read a few articles/books on root cellar design, and l am planning an intake vent at the floor in the NE corner and an exit vent at the ceiling in the SW corner. Most of the books suggest a 3-4" diameter size for these vents. However I am wondering if I can/should perhaps use something smaller, like 2" diameter pipe. We are located in the foothills W of Denver-Boulder CO. Climate here is ag zone 5a (-20F min temps) and it is quite dry and windy most of the winter. I am less concerned with exiting excess moisture than I am over venting and pulling in too much cold air and freezing the vegies. The only downside I have thought of for the smaller vent size is a slower cool down of the cellar in the fall, which I think I can compensate for by running a small fan on select cold nights.  

What do folks think?

The next question will be what to use for covering the stud walls and ceiling once the insulation (fiberglass) is in? Sheet rock is cheap and easy to install, but likely will not hold up well to moisture (not that it will be that wet in there in our climate). Does anyone have anysuggestions for material that will hold up to moisture and be cleanable?

Thanks.
 
Gilbert Fritz
Posts: 1132
Location: Denver, CO
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Hi Steve,

Welcome to Permies!

I'm also in Denver, and I'm interested to see what answers you get. I have to say that I think fiberglass and sheetrock are bad ideas due to water and mold damage. But I hope somebody who knows a lot about this topic chimes in!

If you don't get an excellent answer in another day or so, you can go to the tinkering with this forum thread and invoke the 48 hour rule.
 
Mike Jay
Posts: 246
Location: Northern WI (zone 4)
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food preservation hunting woodworking
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I'm not an expert but I have a root cellar in my basement.  My vents are 4" and I have a fan on the inlet to help cool it in the fall.  Since it's in a house (in a cooler room of the basement on the North side) I may have more trouble getting it cold enough in the fall.  I bet I run the fan for a month (when the temp is lower outside) to get it finally cold enough each fall.  I'd put in 4" ducts, you can always partially block them if you wished they were smaller in the future.

Last winter there were a few weeks where it was getting too cold so I cracked the door open a bit to let it warm up to 34 degrees.  My vents are next to each other (not high and low as recommended by the books) so very little air circulates if the fan isn't running.

My root cellar has a block wall against the exterior on one side and poured cement on the other three sides (I didn't do it, the guy before me did).  But I do like the cement walls.  I would definitely avoid sheetrock.  When/if you get it damp enough for your roots, the sheetrock will probably start to get soft or gross.  You might want a vapor/moisture barrier between the root cellar and your studs to contain the humidity and protect the wood.  A building sciences person will probably chime in to correct or amend this but that's the way I'd be thinking.

I'd probably use milk house paneling as my interior finish.  It's plastic and designed to be washed down.  Caulk or seal the joints to protect the wood studs.

Our "solution" to a lack of moisture is a $9.95 atomizing humidifier that uses a water bottle as its supply tank.  It's so cheap that it doesn't turn off when the humidity gets to 50%, 60% or wherever fancy humidifiers stop.  So it can get us up closer to 90% if we keep it filled.
 
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