Wine Cellar Construction Question (updated with photos)

Converting a 2nd floor pantry into a small wine cellar. Approximately 350 cubic feet. Have decided on a split system for cooling. Really do not want to demo the existing wallboard and flooring to install a vapor barrier but all the guides for split systems stress the importance of doing this. In the group’s opinion, how important is it that the room have a vapor barrier? I’m willing to accept some risk with respect to humidity although this topic (the importance of humidity in wine storage) in and of itself, appears to be controversial. Any comments are welcome and thanks!

vapor barrier mandatory if you are serious about storage and collecting. And proper insulation.


take it down to the studs and do it right, otherwise you’re just asking for more serious trouble. I’d go with closed cell spray insulation, as it doubles as a vapor barrier.


Eric and Alan are correct- do it right from the start and never worry about it again.

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The humidity for the bottles isn’t important. But if you cool the space, you may end up with condensation on the wallboard. And it happens to be a medium that black mold likes to grow in.

But you don’t need to tear it out to put in a vapor barrier. Does your fridge have a vapor barrier? Or a wine fridge that you can buy? Or your cooler that you take to the beach? And there’s your clue. Spray foam is a pain and not necessary.

Just get this stuff.

It comes in 4x8 sheets. At Lowe’s it’s blue and at Home Depot it’s pink. You can get varying thickness and depending on the specific dimensions you want to cover, I’d lap two layers of maybe two inches each. It has an r value of 4.5 - 5 per inch. Close cell spray foam is around 6-6.5 but you won’t get that. It’s very difficult to trim and they usually don’t bring it to the full depth of the stud. And then the stud allows for thermal bridging. So the r value of the wall is less than you’d think. With this stuff, you cover the studs. You will lose space on the interior, but you don’t have thermal bridging and you have a perfectly insulated space inside. And you don’t have to finish it either - after all, the wine cellar is a closet and you’re not going to be looking at the walls when you have shelving in front. If you want to, you can paint it with latex paint. You should be able to do the entire job on a Saturday afternoon, assuming you already have some kind of shelving system.

But your electricity is going to be an issue if you don’t knock a hole in the wallboard somewhere. If you want light in the room, you can run it on the surface, but if there’s a switch or something, you’ll need to make it accessible. Easiest thing to do is to take out the switch and if it’s just a switch leg running down you can probably just run the same switch leg higher than standard height to get your extra few inches. BTW - if you’ve ever been to a restaurant and seen the walk in cooler, this is what’s in the wall. It’s why you don’t need a vapor barrier - it is its own barrier.



Thanks for all of the responses. Will review with the handy man, which is not me! Thanks!

If you’re already going with a split system, the cost of removing the drywall on pantry interior, putting in spray foam or rigid board with VB is not large relatively, and certainly not to racking. And definitely not compared to mold remediation.

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As mentioned a cold space w.o. a vapor barrier is a recipe for mold and even rot in floor joists or studs due to long term condensation. I have seen both. Once you sell the house you could easily end up with a major deal breaker. It is one of those things you need to do right or figure something else out. Wine fridge, offsite storage etc. good luck

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Since you mentioned it is a second floor: my brother in law was going to do something and decided to double check with an engineer who works on foundations to make sure the second floor could take the weight per sq/ft from the bottles… (I am not sure how your house is built, of course… but I thought it was something worth considering…

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My cellar is about 500 bottles over 32 sqft floor area – that ends up being about 63 pounds per square foot (psf). Mine is on a concrete slab, so I’m not concerned, but typical wood joist residential floors are built for 40 psf.

From the original post, assuming an 8’ ceiling and 4 lbs per bottle, you’re looking at 400 or so bottles to hit that 40psf floor limit. (all figures accurate or your money back)

So my advice would be if you were going for fewer bottles than that, then you won’t have to worry. If you’re trying for maximum density and cram 750 bottles in there, then definitely consult a structural engineer.


Once again, all great points. Meeting with the construction guys tomorrow and will probably advocate for ripping out dry wall and vapor barrier. Will also check on the weight question. Thanks again for all of the responses!

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Great point . . . like a library. May need reinforcement.

Keep in mind that 40psf typically assumes 10psf from flooring materials alone.

Ok, after consulting with the contractor, we are taking it down to the studs and floorboards, closed cell spray-foam everywhere. Also examining the structural to ensure that the space can take the weight. Will end up being more than I wanted to spend I’m sure, but it will be a worthy investment. Considered other options but this is what we are going with. Will post pictures and thanks to you all!

curious- where in the room are you intending on putting the split unit relative to bottles? thanks

Contractor working that out and we should have sorted in September

Beach-house wine closet project now complete. Contractor took room down to the studs and reinforced floor joists for the weight plus vapor barrier throughout. I went with the WhisperKOOL Mini Split. I installed the Vigilant racking (not the molding) and we ended up with 500+ bottle capacity total. I hemmed and hawed on removing the window but right now it’s keeping the room between 55 and 60 degrees with no help. Thanks for all the recommendations. Fun project but took 2 months more than I expected. Although it appears tight in the photos, there is plenty of room to walk in and select a bottle.