Hey Michael!

Thanks for the question. I think you are right, depending on the actual humidity of the closet. Ideally you want a humidity close to 70%. Humidity level above this may encourage mold growth on the bottle labels. You can buy a temp/humidity monitor for $20 or so, or spend a bit more and have one that you can monitor remotely via wifi. I really like the Temp Stick unit I used in the article.

My first wine cellar was a concrete foundation block closet similar to what you are describing. I placed commercial wire racking (the stuff used in commercial refrigeration units) in the closet and filled it with wine. The conditions were fairly ideal – 70% humidity and temps ranging from 55 – 60 degrees. I think I covered the block walls with foil-faced polyisocyanurate insulation and taped the seams with foil tape – probably not needed, but I think I did it to give it a more finished interior. I know it might seem like tape sealed foil insulation would create a barrier to the ideal moisture (and temp), but the concrete floor wasn’t sealed (I think I used foam exercise tiles to cover it) and probably equilibrated with the floor/block humidity levels fairly readily. I think I have a photo – I’ll upload what I have.

Let me know how it goes.

Hi Silvia,

I just noticed your question about fastening the cedar boards on the inside of the cellar. Yes, I first secure the cedar boards to the wall studs which does penetrate the vapor barrier. I then use shorter screws to secure the racks to the cedar boards.

It is true that the fasteners holding the cedar boards up are passing through the vapor barrier, but the end result is a very small total penetration surface area compared to the entire envelope. There isn’t a good obvious workaround. I guess you could install a strip of something like butyl flashing tape over the vapor barrier in the areas (over the studs) you intend to drive fasteners, in attempt to better seal the fastener track, but I don’t think its necessary.

I suspect this fastener through the vapor barrier question is very similar to adding sliding to a home. Home siding fasteners also pass through the building’s vapor barrier, but collectively do not significantly reduce the effectiveness of the barrier.

It is a good question, but my guess is not a significant problem.

Thank you Gary! Reading the book now;-) I did also want to ask you, given you are drilling into the cedar and then the racks ontop, doesn’t that create penetration into the vapor seal? What do you recommend?

Hi Silvia!

Thanks! Having a wine cellar is such a joy, I’m happy for you guys – you will love it. I’m happy to help with any questions or issues. Richard Gold published an excellent and entertaining book How and Why to Build a Wine Cellar ( I just realized I never mentioned it in the article) for more reading. It is an excellent resource written by an enthusiastic scientist, DIYer and wine lover – a great read.

I really like temp stick, it’s worked well for me and offers a free (no subscription) website to access your sensor from the web without a phone.

A few words of advice as you start the wine cellar build:

• Vapor and air seal the space with a poly sheeting or similar on the warmest side of the build to prevent warm, moist air from entering the wine cellar. If you skip the vapor/moisture barrier it will be difficult to reach the 55 – 60 ideal temps, the system will use much more energy with the cooling unit running longer and more frequently. You also risk wall damage as warmer air will release water into the walls as it moves in and is cooled. The vapor barrier is also important to keep the cooled, moist air within the cellar space in dry, warm climates.
• Use enough insulation. Rigid foam works great and has very high R-valves so you can limit the insulation/wall thickness. Fiberglass between studs is OK, but all of the uninsulated studs reduce efficiency and create insulation gaps. I used foil-faced polyisocyanurate sheets, which I recommend. They are easy to purchase at any building center and offer some of the highest R-value. Foil faced products, if the seams are taped also provide a moisture barrier.
• Don’t use drywall to finish the walls on the inside. Drywall doesn’t handle moisture well over time – even the “green” drywall. I’ve always used cedar paneling or boards. If you want a smooth wall board, look at one of the tile backer boards like Hardibacker, GoBoard or similar.

Have fun and please feel free reply with any questions, and if you like upload a few photos of your project.

Gary

Hi Paschal,

I’m not sure which dimension you are referring to.