Wine Cellar Vapor Barriers

Keeping your wine cellar insulation dry


Once you’ve built your walls you’ll need to add a vapor barrier. The vapor barrier serves to prevent the cooled air from the cellar from leaking into the walls.  It’s not really designed to prevent heat loss, which will be modest, but rather helps to prevent cool air from meeting warmer, moister air in the walls, which causes condensation. That condensation can lead to rot in your studs, but more damagingly, it can get stuck in your insulation, reducing its effective r-value, and setting you up for insidious mold issues! Don’t skimp here!

In order to be effective you’ll have to put a complete vapor barrier up in your cellar, which is easy to do since a vapor barrier is essentially a thin plastic sheet nailed to the studs over the insulation. In the case of your foam board insulated foundation walls you won’t have to worry about reduced r-values, since the foam boards are impervious to wicking, but the mold issue is still worth taking care of. So, wrap that vapor barrier all around your walls.

Another layer of protection one should consider on those exterior walls is applying a paint like vapor barrier before you apply the foam panels. It’s an easy step, definitely DIY, and will help keep moisture from wicking through the walls and into your basement, even if your cellar is nicely sealed.

And speaking of sealed, there’s one more step to completing your properly sealed walls: Taping the seams! Getting just a bit a head of myself here, though, since we should talk about sheetrock for your walls.  Since the cellar is maintained at fairly low temperatures the dew point is also fairly low, causing potential humidity conditions that could prove problematic for wood siding (although I have had cedar siding in my cellar for years without issue) and even for regular sheetrock. I strongly recommend using the green or blue waterproof sheetrock that is typically used in high moisture areas such as bathrooms. It might be more expensive today but you’ll save yourself headaches for years! Once you get your rock up, make sure to tape all the seams with waterproof plastic tape to ensure that you have a near perfect vapor barrier.

Chapter 3: Ceilings and Lighting in the Cellar

Return to Building a Wine Cellar

This article is part of a series on building your own wine cellar:

I.    Building Wine Cellar Walls
II.   Wine Cellar Vapor Barriers
III.  Wine Cellar Ceilings and Lighting
IV.   Wine Cellar Flooring
V.    Wine Cellar Windows and Doors

Similar Topic:

Cellar Temperature

Mentioned in this article


  • Snooth User: civiletti
    192021 20

    Folks should be cautious with polyethylene vapor barriers. Used inappropriately or executed poorly, thay can cause, not prevent rot.

    Walls need to dry to one side or the other or to both sides. If the wall-side opposite the cellar is conditioned living space, then moisture should be able to dry to that side. If the cellar wall is against below grade masonry, or if has a vapor barrier applied to the other side, the cellar wall cannot dry to that side. Poly would trap moisture in the wall, promotoing mold and rot, especially with all that fiberglass between the studs.

    There is no simple solution for all situations. I would suggest foam insulation against masonry, rather than fiberglass. Even cellulose fill performs better with some dampness than does fiberglass. If you do use poly, seal it very carefully, as moist air will move through any small openings. If the temperature difference is great enough, the moisture will condense, possibly soaking the wall interior at that point. But most basement masonry walls transfer moisture to the inside, So if you have a perfect vapor barrier inside your stud wall next to the the masonry wall, moisture form outside will build up and rot the wall. Another approach is to leave a ventilated space between your cellar stud wall and the masonry wall. Then moisture from both sides can dry to that space.

    Aug 31, 2010 at 9:29 PM

  • Im just curious, it keeps getting mentioned about the spray foam. Icyene is the most commonly used and available. But this is NOT a vapor barrier, it is basically an airtight seal. MEaning no air in or out. It also is a thermal barrier. So I guess if your wanting an air and thermal barrier it is the best thing to use. I have looked inot the construction of a "True Cellar" when i return home from my current adventure. The netire cellar will actually be below ground and spray foamed all over the struxcture, but i will leave a dirt floor in the bottom. What are the advantages of using the spray foam over normal insulation or insulation board? I would think if its almost a solid barrier it would NOT be that good. Even plastic allows the temps to poass, but the foam wont. We cover the tents over here in IRaq with Icylene Spray foam, called "tiger foam". And it works believe me. 150+ outside of the tent and 2 AC's inside its still nice.

    Aug 31, 2010 at 11:00 PM

  • Snooth User: civiletti
    192021 20

    Foam insulations are not all the same. They vary in R-value, water vapor permeability, and installation method. The general advantage of spray insulation is seamless installation. Foam sheathing can be taped to provide an air barrier - if you do a good job.

    Icylene is a water blown open-cell polyurethane. It has a lower R-value than more conventional polyurethane [which is considered a vapor barrier], and it is quite permeable to water vapor. Also considered impermeable is foil-faced board with metal tape, which stops water much like polyethylene sheeting.

    Sep 01, 2010 at 12:13 AM

  • Snooth User: dvogel001
    442684 8

    The other suggestion that I have for the walls and ceiling is to use a good exterior latex paint which will act as an extra barrier to moisture seeping into the walls instead of a indoor paint. Afterall the exterior paints are designed to resist moisture.

    Sep 01, 2010 at 1:37 AM

  • Snooth User: greyfox
    521200 2

    I built an entirely brick wine cellar in an underground basement room 4 years ago. The walls and floor were poured concrete so we bricked over them. I have not had any humidity issues whatsoever even though I had a dehumidifier installed along with a cooling unit. Hardly ever use either one - temp stays pretty static between 58 - 62 degrees with humidity levels averaging 50-60%. The lighting is low and the room is very stable - no vibration. My wines lie inside holes in the wall and are aging gracefully!

    Sep 01, 2010 at 1:21 PM

  • Snooth User: schellbe
    Hand of Snooth
    247770 225

    Can you make any comments about how cellar construction changes with dry climates? Are vapor barriers necessary?

    I am happy with my passive cellar that ranges from 52 degrees in the winter to 67 degrees in the summer, but add humidity year round, although more often in the winter. Outside relative humidity here is probably 20% year-round. July temp 88-54, Jan temp 32-12.

    Just curious if I were to build a non-passive cellar, what special considerations would be involved.

    Sep 19, 2010 at 11:36 PM

  • Snooth User: fbrack
    151974 1

    Yikes, are you showing a vapor barrier on the INSIDE of the wine room? I can't tell from the picture, and you don't say. For a cooled wine room with fiberglass insulation, it is essential the vapor barrier be on the warm side, because otherwise any moisture seeping into the wall from outside will hit the vapor barrier against the cold wall and condense, causing mildew and mold inside the wall. You want to stop external humidity before it gets to the cold wall, so you put the barrier on the warm side. See "How to Build a Wine Room" at, step 7.

    Dec 01, 2010 at 3:40 PM

  • Snooth User: schellbe
    Hand of Snooth
    247770 225

    I've read all this, and I am convinced now that vapor barriers are unnecessary for dry climates. If the inside of the wine cellar is cold and wet (60% humidity) and the outside is warm and dry (20% humidity), moisture will travel through the walls and hit the warm dry outer wall, and heat up, hitting air that can hold more moisture.

    If anything, a vapor barrier might be appropriate on the inner wall for outside walls of the building, as warm moist air would not cool down and condense when hitting cold outside walls in the winter.

    I have enough leakage in my passive cellar that the added humidity in my cellar does not seem to lead to condensation on the outside walls.

    Just remember to faithfully humidify your wine cellar, if that is necessary.

    Dec 01, 2010 at 5:11 PM

  • Wow... the vapor barrier must go on the "warm" side of the wine cellar walls... not over the insulation as shown. This is a big error and can cause mold and mildew to grow in that insulation. The inside of the cellar is climate controlled. Never put the vapor barrier on the warm side. See info on building your wine cellar at

    Jan 18, 2011 at 2:02 PM

  • Oops... I mean't never put the vapor barrier on the "cold" side!

    Jan 18, 2011 at 2:03 PM

  • Reading all these comments it becomes quite clear why people are not sure what to do with their wine room. To reiterate the question about the vapor barrier shown above, I agree with those above who are also in the wine cellar industry, it must go on warm side, NOT cold side. And yes a vapor barrier IS essential. If you build without a proper vapor barrier, you are taking a significant risk and it's almost assured to have issues. The question about spray foam, that is a common question, the difference is closed cell vs open cell, and the density of that foam must be properly stipulated. Closed is going to provide a proper vapor barrier applied in propery density and thickness. Again I cannot stress how important these items are for a proper wine room construction and performance. We are one of the top wine room builders, designers, consultants in south Florida we have to ensure this proper construction on every project we do. We are also hired as consultants for insurance companies as well as called on for wine cellar repairs, mold issues, catastrophic failures etc and we have to source the rooms failures and almost every time it is due to improper insulation, lack or air tight construction, or something related to lack of knowledge. I cannot stress how important it is to hire a proper professional to build a wine room, there are a 100s of items that must be understood to build these properly. Too many contractors read a couple things online and think they "get the gist of it". Don't fall victim to this, hire a professional! If they say they have done dozens of wine rooms, ask to see their portfolio, talk to an old client, do your homework. We look at minimum 4 rooms a week that are failing due to not hiring a proper professional. Feel free to contact us at or info@winecellarinternational. (Ft Lauderdale, Florida)

    Apr 30, 2014 at 10:09 AM

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