I have not really found this addressed online.

I a building a passive wine cellar in a storm shelter/safe room. It is all below ground, 10 x 13 and has 10" concrete walls on each side, a concrete floor, and a concrete ceiling. 3 of the 4 walls are completely backfilled with dirt, and 2 of those 3 are under the garage so they get no sunlight exposure, and the 3rd gets very minimal. The 4th concrete wall has living space on the other side, as well as the wine cellar door. The ceiling is actually the garage floor.

Since this is passive, and because of the location, the concrete walls and the dirt side are really the cold side and the inside of the wine cellar is the warm side since there is no cooling unit. At equilibrium, the temperatures would be close to the same, however as heat is introduced into the room, from either people or from the heat from the living area through the 4th wall, the general energy (heat) transfer would be from the living area through wall 4 into the wine cellar, then into walls 1-3, which are the coldest in all climates.

So the question is:

do walls 1-3 need any insulation since they are the coldest point and their temperature will change very slowly due to the thermal mass of the concrete and the dirt behind it, and since I want to conduct the heat to out quickly?

do walls 1-3 even need 6 mil vapor barrier?

my current thought is:

6 mil vapor barrier on all 4 walls and the ceiling, up against the concrete, followed by framing.

Insulation on the ceiling and both sides of the living space concrete wall, with the kraft vapor barrier of the wine cellar side insulation up against the 6 mil VB and the concrete side, which would leave the bare insulation against the sheetrock.
Then use green board sheetrock on all 4 sides plus the ceiling.

Other alternatives would be to insulate only the top several feet of walls 1-3, since it could be warmer.

What do you guys think?

Thanks

Have you taken temp measurements on the warmest part of the room? You can try a vapour barrier on the wall that is warmest or the ceiling but I guess others will chime in with your first hand experience.

It’s hard to comment without knowing where you live. Although, I recommend active cooling unless you live in the mountains, Alaska or in Canada.

Do not put the vapor barrier directly on the existing concrete wall. It should be on the outside face of your cellar envelope. With 4 different temperature and humidity zones around your cellar, you will definitely need a good VB.

Leave a 1" - 2" space between the new walls and the existing concrete walls to allow moisture in these walls to weep without transmitting to the new walls.

Get Richard Gold's book - How and Why to build a Wine Cellar. he talks about the thermal properties of soil, heat transfer, etc., and recommends building a passive cellar if you can. He also includes data on his own area up in Mass. But you need to do some temp monitoring on your own.

Personally, I would also measure the summer temp in the garage because you might be surprised. My mother lives in Michigan. Her basement is pretty cool. However, her garage gets incredibly hot - most of them aren't insulated and they just soak up the summer heat. So the basement wall nearest that is actually much warmer than the basement wall receiving southern exposure, which is covered by plants and grass.