Wine cellar- R19/30 vs spray foam

WINE TALK
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First- I just wanted to thank all of those who have posted about building wine cellars. Super helpful.

I am finishing construction on a wine cellar that has r19 in the walls and r30 in the ceiling. The floor is slab, and the ceiling is below the attic. I live in humid Georgia. There is a vapor barrier around entirety of the space.

I am getting ac unit installed and the hvac company is saying I should tear out the insulation and put in closed cell foam.

I understand there is a benefit to closed cell foam and wish I would have just done it to start. But now I’m trying to figure out whether it’s worth $2-3k to change it.

Any general thoughts on whether this is overkill, or will I be kicking myself in the future for not doing it now while it’s just Sheetrock I’m tearing out.

Thanks!

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I recently built one and closed cell foam was recommended by all three companies I spoke with. What is your wine cellar/collection worth? That 2-3k may not seem like as much money 10-20 years from now.

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I have 2x6s with fiberglass batts that works just fine. As long as it’s reasonably air tight I am not sure why you would tear up completed construction.

1 Like
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So I had our contractor cut into the dry wall just to confirm the insulation was r19. It definitely is r19 but I’m pretty sure the vapor barrier is on the wrong side of the insulation. Can anyone confirm?
392B11BC-2A97-4B4C-8E37-4D12D699A003.jpeg

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For Georgia yes vapor barrier is on the wrong side.

Please see: What Happens When You Put a Plastic Vapor Barrier in Your Wall? - Energy Vanguard

Also, refrigerated commercial spaces put 2” thick insulation board under a slab for foundation insulation. May not be worth it to tear up your slab but worth knowing.

Product like:

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INground & refrigerated really helps in Miami ! [wow.gif] [cheers.gif]

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With the proviso that I have no experience with these materials whatsoever, and that I could be completely wrong about what follows: If the slightest little bit of moisture gets into that cellulose, then you’re gonna start growing mold & mildew, which means that your wine will effectively be surrounded by wet rotten cardboard, and that strikes me as an environment which would be more than happy to start producing chlorine compounds such as Tri-Chloro-Anisole.

Just doing some cursory reading on the subject indicates that cellulose is “perfectly fine” as long as it is “installed correctly” by “people who know what they’re doing” and who actually care about the final product.

But so far, it appears that you’ve been dealing with people who don’t know what the heck they’re doing, and don’t give a damn about the final product.

In tropical rain forests such as the state of Georgia, a glass-based product, like Owens-Corning pink, seems as thought it would VASTLY MORE RESISTANT to growing mold & mildew than would be cellulose.

Cellulose might be fine in, say, Arizona, or New Mexico, or California, but I would be deeply skeptical about introducing cellulose into the tropical rain forest.

PS: I may have misunderstood one of the comments above, but I would never mess with a slab if it were touching grade, and especially I would never try to alter a slab if it were below grade.

Even just at grade, a slab, which is merely touching soil, ought to offer cooling value in the summer, and heating value in the winter. [Obviously I’m assuming that the slab is covered by a roof, and is not subjected to sunlight.]

A slab, particularly when it’s below grade, is a natural root cellar; relatively cool in the summer, and relatively warm in the winter.

PS: I really ought to confess that I SMDH every time I glance at one of these wine cellar threads, because invariably they are riddled with anti-Physics anti-Chemistry anti-Materials-Science nonsense.

It’s almost like reading a nutrition forum where a bunch of psychosomatic hypochondriacs are quarreling about vitamin pills.

I’m starting to conclude that the wine-cellar-building industry in general is roughly on an ethical par with the snake oil salesmen in the nutritional supplement business.

And at this point, I suppose you could throw pretty much the entirety of the Pharmaceutical Industrial Complex in there with them.

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I suppose the big difference there would be that the Pharmaceutical Industrial Complex isn’t so much anti-Physics & anti-Chemistry & anti-Materials-Science as it is simply anti-Human.

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If this pic is taken inside the cellar- yes, the vapor barrier is on the wrong side of the insulation.
VB should be against the “warm side of the wall” & the insulation on the wine cellar-side of the VB. This keeps any condensation out of the insulation.

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I had fibreglass batts in a home-built wine cellar at my previous house, but I had closed cell polyurethane foam insulation put in when building a new cellar at my current house. I am really pleased with the foam - my rough assessment is based on how frequently the cooling unit kicks in, which is much less than previously.

My understanding of the foam is that is also acts as a vapour barrier, i.e., no additional vapour barrier is needed as it is impermeable to moisture.

If I had had a room in which the fibreglass batts and vapour barrier were already installed (correctly), I doubt if I would have been bothered to start all over again. But as noted above, if the vapour barrier you have is on the cold side of the insulation, it seems to be the wrong side.

One thing to note: if you do go with foam, my understanding is that it must be closed cell for thermal insulation (care with not confusing it with open cell insulation, used for sound suppression).

The drawbacks of the foam insulation for me were the cost and the awful-smelling and presumably bad-for-you fumes which are emitted while installing - so best to be out of the house and to ventilate well afterwards.

The broad guide below might be useful:

The section on insulation includes comment son the correct side for the vapour barrier.

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First question - is vapor barrier on the outside of the insulation? You want it on the warm side (i.e., away from cellar).

Do you keep your house air conditioned? If so I wouldn’t worry a huge amount about closed cell vs. batts. Yes, if you were starting from scratch you’d get 95% recs for closed cell. But you didn’t. And think the difference isn’t worth the effort. First, you have enough insulation. Foam isn’t going to change the r value much (yes, you could get it higher by filling the entire space). And for moisture you have the right barrier.

But keep this in mind (to settle it). If you’re keeping your house at 75 or so in the summer with AC, it already will have humidity removed and have only about a 20 degree delta with the cellar. So you’re not likely to be seeing either huge amounts of heat getting into cellar or huge amounts of moisture and condensation. There are online calculators for this, and an expert can tell you the right answer, but IIRC when I looked at this if you have 75 degree air cooled to 55 degrees with the same water content - i.e., the condition of the wall of the cellar - you’re still above the dewpoint so shouldn’t get much condensation. And that’s worst case, because the insulation means the vapor barrier should be well above 55 degrees when the “damp” house air contacts the cold points.

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Great points!

Unfortunately, the previous builder put vapor barrier on the inside and I apparently didn’t catch it. So now I have the choice and I believe it’s cost equivalent to do closed cell foam vs batts.

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When you say the previous builder did this, does that mean all of your exterior walls have a vapor barrier directly behind the drywall? Is the cellar floor a slab on grade with an unconditioned attic directly above the cellar ceiling? How many walls of the cellar are exterior walls?

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Good question- the exterior is spray foam. Why they didn’t spray foam the wine is beyond me. But it’s a long story. The floor is a slab. So the only place they were hanging a vapor barrier was the wine room.

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So they just build some interior partition walls to frame out the cellar? What’s on the other side of the ceiling, and unconditioned attic?

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You got it- unfinished attic. The house ac unit is up there too. It’s where the wine room ducted system will go.

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Whoops - sorry. I didn’t follow upthread closely and thought that was someone else.

Yeah, with vapor barrier on wrong side you probably ought to redo it anyway. Might never be an issue, but probably better to avoid. Frustrating to redo work, but go with closed cell.

Also go with greenboard or whatever the drywall used in bathrooms is called now. Extra help on combatting any moisture.

Ripping out also means you can do whatever wiring you might want/need. Think about lighting and auxilliary outlets for anything you might need, such as rack lighting.

(And now seeing it’s up against attic - definitely make sure there’s as much insulation as possible in ceiling if that’s unconditioned space.)

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If you have spray foam (assuming closed cell) in the walls of the cellar that are also exterior walls of the house, then I would not be concerned about those. Closed cell is a great air and vapor barrier. For your interior walls where they put the vapor barrier on the cold side, you will probably be ok. The dew point of 75 degree, 50% RH air is 55 degrees. So if you had no insulation, just a vapor barrier on those interior walls, then you would see condensation on the barrier with those conditions. At 73 degree temps, 45% RH the dew point is 50 degrees. I think those walls are manageable as is. The attic is what concerns me. The dew point of 95 degree, 45% RH air is 71 degrees. That is where your greatest potential for condensation is. Contractors love to place HVAC equipment in unconditioned attics, but it is the worst place to put it. If it is the only place possible, make sure they insulate the crap out of the ducts and the unit.

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I’ve put a few cellars in our houses over the years and learned a few things. I also have a strong inclination to built thought right and work very well. I would always use closed cell now for great insulation (key for any cellar and energy use) and solves the vapor barrier issue. When mold or moisture gets into a cellar never ends well and usually requires complete tear out.

Second a mini split cooling system is great for any small to mid sized cellar. Cost effective, reliable and quiet. Need a coolbot device to trick the thermostat given mini splits are for generic results use.

Lastly get a commercial HVAC (or one that does commercial and residential work) firm to install the cooler.