Good idea Laura. Do you know what the ground temp is there?

Springtime is correct, the first question is your ground temp. In SC, the ground temp is in the 60s year round, low in the winter and high in summer. In Minnesota, you can get freezing temps several feet below ground. Northern California, I have no clue what to expect.

If there will be finished space outside any wall of the cellar, then you'll be fighting 72 degrees on at least one side. It's a noble thought, but I think using a small chiller unit would be a prudent decision. Our cellar is in the basement, 2 outside walls, sprayfoam insulation. I'm sure it costs us money to keep it at 57 degrees, but our electric bill is not very high compared to our neighbors.

Thanks for the advice, I'm not certain as to our soil temperature, however while the days are hot here in the summer, it is quite cool in the evening, so I expect that the ground temp here is at least a bit lower than yours in SC.

There is an often referenced book on the topic of building a passive wine cellar "How and Why to Build a Wine Cellar" by Richard Gold, however after reading it I'm still not certain how to proceed!

A few specific concerns:

- From an early design perspective, should we plan it with three outside walls, or two?

- Is there any advantage gained if one, or two of the exterior walls of the cellar are under the house and not a part of the external foundation?

- If there is an exterior wall of the cellar under the house that is not exposed directly to the heat of the sun, is there anything we would do different regarding insulation?

- Can something be put in the concrete between the cellar and the rest of the basement to prevent heat transfer through the concrete from the rest of the heated basement?

We would like to build it to the best possible specifications for a passive cellar, and if are unable to get it to a cool enough temperature (we would be happy with about 60-62) then we could put a cooling unit in later.

I'm strictly in the peanut gallery on this subject. But I'd think you'd want as many sides of the room against the soil as possible. Any wall that has heated space on the other side needs to be insulated. If the walls/slab are poured concrete, having that thermal mass will buffer against temperature changes from going in out of the room. Thicker obviously is better, though I'm not sure what the point of diminishing returns would be.

Do a quick Google search and you can find out what subsurface temperatures are for your part of the world. There are a lot of maps that are used in designing ground-source heat pumps.

Even the exterior walls need to be insulated to build a passive wine cellar to keep the temperature constant as the top part of the soil is much warmer, and the sun against the side of the foundation transfers a lot of heat. We plan on insulating both the interior and exterior of the walls, but I�m curious as to whether the exterior walls under the house that are not exposed to the elements should be treated differently than the exterior wall against the sun.

I have been Googling soil temps and I�ve read conflicting information from 55-63 F.

On another thread Lavender Lass just asked me this:

Is having a cooling unit a large expense or are you trying to make the cellar more environmentally friendly...or both? If you can design it the way you would like to, I think it would give other people an idea what they would like to have, too.

Even with a warmer ground temperature, I think insulation should make the difference. Wouldn't thicker cement walls keep everything cooler, too? Don't earth homes work so well, because they're insulated and save on heating/cooling...in lots of areas, including California...and and even out in the desert? Maybe that could give you some ideas?

We are trying to make the cellar more environmentally friendly, while at the same time reducing some of the expense of this little luxury. The cooling unit is a large expense ($2500+) as a regular AC unit cannot be used for several reasons. And then the cooling unit causes its own issues including noise, and needing to vented back into the house as the models that can be vented outside are even more costly.

I believe it is possible, and I�m just hoping to hear from someone who has accomplished this! Anyone out there share my habit of collecting much too much wine?

Laura- Can you post this question on the kitchen forum, too? Maybe you'll get more responses, especially is you ask it more like...I love cooking with wine...anyone have a wine cellar to store all their wine? How do you keep it cool? :)

Kind of hard to tell what the situation is from your comments.

Thull has the best advice. You want as many walls touching the ground as possible with NO insulation between concrete and Earth. The only insulation should be between the cellar and conditioned space (or exterior if not below grade). The most confusing comment is in regard to sun hitting the foundation wall. The cellar should not be located on an exterior wall that receives sunlight, that would make it above grade and you are trying to get it below grade..

I picture a jog or bumpout in your foundation that extends into the buried ground or below grade. This would give you three walls and the floor to be coupled to the ground (again no insulation between concrete and ground). You would need to insulate the ceiling (if conditioned space above) and the wall that connects to the basement conditioned area. You would want an insulated door and pay VERY close attention to air sealing this room.

As to the comment that Earth coupled homes perform better.. It might be that an earth coupled home would perform even better with some insulation between it and the ground but it really depends on the climate and situation. In your situation, you want the cellar closer to the ground temp than to the human comfort zone temps (68-75), which is why you dont want insulation between the walls and earth for the cellar but usually do for conditioned space.

The concrete walls provide thermal mass, to keep the temperature constant. If your soil temps are in the range that you want the wine cellar (if the 55-63 is accurate, then they are), then no insulation on the concrete side is correct.

Being in SC, our ground temp is a little warm, so we still insulated the Concrete side.

As for the sides facing the conditioned part of your basement, I'd build a standard 2x4 wall, sheath it with XPS facing the cellar (builder's tape on the seams) and spray foam the stud cavities. Don't forget to do the same thing on the ceiling! Then use a mold resistant wall board and exterior paint to finish it. Add a good quality exterior door with no glass.

That will be about as consistent temp as you can get. You can install a conditioner unit, set the temp to 57 and in may never turn on, or just turn on infrequently.

Good luck, life's too short to drink bad wine! (my wife's saying not mine, I'm a beer guy)

Brian

Springtime homes - I really really appreciate your feedback, however you are not entirely correct. I have been reading up on how to set this up and the upper 1/3 to 1/2 of the foundation needs to be insulated to prevent heat transferring from the upper parts of the soil and the exterior foundation. Unfortunately we are forced to either have this at the west or east side of the foundation (one wall) so that creates additional difficulties.

It is the bottom portion of the wall and the floor itself that keeps the room cool.

The room itself will be close to air tight due to a vapor barrier and a well insulated exterior door entering the room. The walls shared with the house and the ceiling will be VERY will insulated, to the highest R value that we can fit into the space! :)

I'm really curious if there is anyone on GardenWeb who has built a passive wine cellar themselves and if they have any specific tips beyond what is standard. There are 3 main questions I have as well.

1. For instance. I wonder if there is a way to separate the concrete floor from the rest of the basement while the foundation is being laid so that there is not any heat transfer through the concrete in the rest of the basement?

2. If one (or two) of the exterior walls are completely under the house and not shared the the rest of the homes foundation, then would their be any difference in how you insulate the concrete from the exterior?

3. And, should I plan for two or three exterior walls? The problem with planning three is that it would make it very difficult to then add a cooling system if this didn't end up working.

bdpeck-charlotte - Thanks for the advice, your post came up while I was writing my last one and I didn't see it. You are exactly who I was hoping to find with this post, someone with a passive cellar in a warm climate! :)

You mention an AC unit, do you have one in your cellar? If so, is it just a standard one, not one meant for a wine cellar? And what is your annual temperature variation (summer/winter)? I'm curious to hear more as I'm assuming your soil is warmer than ours as we have such cool nights during the summer, and well, all year round! :)

Regarding the interior wall construction we are planning on a staggered stud 4x6 construction, with spray foam insulation, and maybe regular batting on top of that. Then a vapour barrier and the rest of the overall process you describe, repeated of course on the ceiling.

For the exterior wall, we are planning on using rigid foam on the outside top half of the exterior walls, and then likely angle it out as is recommended in the below book (the only reference I can find on the subject, and one that many other forums seem to point to).

bdpeck-charlotte - I'm curious what your cellar temp ranges from throughout the year with your setup?

Sorry for the bad advice. I can understand the theory but iam not sold on it. I guess it really depends on how deep it will be and the soil temps.. To seperate the slab i think you could use 2 inch polystyrene .

The Cellar is 57 degrees, 24/7 365. We've got quite a bit of foam (spray and board) insulation. The Chiller is from Wine Guardian. It's a ducted self contained unit, meaning, it's like a wall unit that it has the refrigerant already in it (you don't need an HVAC guy to install it), but it uses normal ductwork (we used insulated flex duct) to have a supply and return in the cellar and a supply and exhaust (can be to outside the home) on the compressor.

Our temps in the summer are 90Day/70Night and winter 40Day/30Night for the extremes.

I see how the design tries to keep the first 5 feet of foundation from affecting the temps, but I doubt that will work. The concrete should all end up the same temp, with only the smallest variation... and that temp should be the temp of the ground.

Thanks bdpeck-charlotte!

I think we are going to try to set it up so that it is passive and then if that doesn't work put in a cooling unit as a last resort.

Does your unit exhaust to the outdoors, or to another room within your house?

I put the supply side for the compressor in the tasting room and the exhaust in our very large main room right by the air return for the HVAC. Our basement is cool enough that the heat from the unit is welcome down there. It's tough finding a duct exhaust hood for an 8" duct, so going to the outside is tough.

Where the exhaust of the unit goes is one of our issues. It will be next to the media room, and the noise would drive my DH batty!