Hi all,
Wondering if anyone in the forum has pulled off a passive wine cellar in Virginia? I’m in the northern part of the state and have a 4 to 5’ deep basement. I ran a bunch of insulation, heat loss, and soil models and came to the conclusion that it’s possible, but just a hair warmer than I want. Looking to make a 500 to 600 bottle large closet cellar, ~200cuft interior volume.
My deep-soil heat sink will be around 57F and the measurements I took in the basement and outside support this. House is usually cooled to 74 and heated to 70. Based on my models, I’m showing about 59 to 70F as a temperature range, independent of how much insulation I use. There just isn’t enough heat sink from the ground to make a huge difference. That said, the range of only 11F annually is pretty good. Going to R50+ everywhere only pulls the high temp down to 69F. Again, just not enough heat sink in the floor.
So no real benefit of super-insulating with spray foam ($2500 DIY, more if done by pro). I’m leaning towards hitting R35 to R40 with mostly rock-wool (~$600) and maybe using a small active unit set to 60, which would probably not run much at all.
Any advice or experiences shared are appreciated. Looking to get started on this in the summer.
I am in Southern Maryland and have a passive cellar. I have probably 1.5 ft above grade. I will be the first to admit that I would like to do a few things differently if I had the chance to do it over but even still don’t have many issues. My cellar is in the north east corner of the basement and thanks to the trees, gets very little direct sun. Not sure how much difference it makes overall but there is one small window in the space so I am happy to limit that, while also using a curtain.
The heat and AC both run into the basement. I have closed off vents in the past and not noticed much difference in cellar temps. In most years, I top out at 68 measured at eye level by the door. Its colder towards the floor that I didn’t cover as I didn’t want to impact the heat sink at all. Just painted the concrete. On the cold side, I can get to a low of 56 but in a year like this, it’s more like 60.
My insulation isn’t near what most recommend. This is one area that I would like to redo but too much work to do so and honestly, given my yearly temps, I am not motivated to do so.
Hey Anthony. I had a passive cellar here in Alexandria for many years and it worked fine. I ended up going active on the cheap – the room is mostly below grade with a window high on the wall and I stuck a tricked out a/c unit in it. It was easy and cheap to do, but if I were in your situation I would not have worried a bit about staying passive
Here in MN I have a separate closed off, unheated 800 sq ft mechanical/storage area that is completely below grade. I have waist high cabinets open on the bottom to the concrete floor,and their current temp is 59 degrees. In the center of the room area it’s 64 degrees at eye level due to the heat transfer from the water heater and the furnace. During the summer with the furnace running in AC mode and the cold air that is escaping under the door to the basement, the ambient room temperature is usually cooler, with the cabinets are still around 60 degrees. If the below grade area is smaller, do not discount the impact of the furnace running in AC mode.
Thanks guys. The plan may be to split the difference (one layer of Thermax/Rmax + rockwool) and give it a year passive with a spot already framed for the cooling unit should I need one. The fact you guys had any success with basically the same soil temps gives me some hope.
Ron, to your point, I am near the mechanicals and I can see on my datalogger when the furnace kicks on (and last year when the AC kicked on). The air temp in the basement (no vents, just the ducts running elsewhere) jumps when it runs. When we redo the basement, there will be an insulated wall isolating the mechanicals, then a small common area, then the cellar. So I should be pretty isolated from that effect except for lateral heat flow through the slab. Nothing I can do there. Thanks for the help.
I’m in Central Virginia with a subterranean passive cellar. Maybe one day I will wall it off and cool it, but for now it’s the corner of the utility room and it seems to work fine. I haven’t tested the temp, but it’s definitely cooler than our living areas year round. I think you’ll be fine–these beverages are tougher than we give them credit for!
I’m running the High Efficiency furnace which seems more contained. What I seem to notice is in the cooling effect of the exterior of the ducting during the summer.
Key things I learned from Richard M Gold’s (obsessive compulsive but essential) guide to passive cellars and experience building mine:
The ground temperature gets very surprisingly warm even 5 or 7 feet down in the summer time along the Eastern Seaboard – into the high 60s. Yours will be warmer than mine (in the Catskills) or Gold’s (in western Massachusetts).
In summer time, your only friend is the floor, so if you make the room too small, the only surface cool enough to counter the temps of the walls and ceiling will be too small. 200 cubic feet implies a very small floor.
Concrete is a better conductor than you’d think, and it will convey some heat through the basement floor even if you’ve insulated the hell out of the walls.
There’s a point of diminishing returns with insulation, as you realize.
My wine room drifted up to 67/68F in August and September. I can live with that, but it was higher than I hoped. I assume that in Virginia you’d end up higher than that. So I think you’re right to build in a small cooling unit.
In my experience, it really helps if you hit bedrock.
If the bottom of your basement is concrete on top of gravel on top of soil [or clay or sand], then your results will be much more variable than if the concrete were sitting directly on bedrock.
Also, if it’s a new house, then you might not yet know how well the house was graded & waterproofed, and until the next Cat 4 Hurricane rolls through town, you won’t learn that your basement was built without a surrounding water management system [which would have involved putting down a great deal of drainage pipe and crushed rock] and that your basement is in fact just a great big swimming pool beneath your house [waiting to be filled with water].
Developers love to cheat on the stuff you can’t see, like drainage pipe & crushed rock.
Used a passive cellar in NoVa from '00-06 and then in PA from '06-‘09 (with each floor around 8’ under grade). I built a temp and humidity controlled cellar space in '09. I have not seen any problems with the wines I kept in the passive space.
Thanks all. I have Gold’s book and have read it and a lot of the other threads here and at CT over the last year or so.
Basement is pretty good, water-wise. We are atop a hill and the house is pretty well graded away except for two spots, which just efflouresce, but don’t leak. We’re lucky in that regard. House is from the late 70’s but very well overbuilt. They insulated the concrete block foundation for one (R8 or so, but better than nothing). I do not believe we have a drainage system, but whatever is there works. We’ve been here over 10 years and plenty of heavy rainstorms and no flooding.
As to the R value of the slab, I’m getting measurements that are closer to R25 or R30 than the R2 or R3 that a concrete slab should be (Gold recounts a similar measurement, but doesn’t go into details). I have a few temp sensors scattered around and outside to record some data before I commit to all this (full disclosure: mechanical engineer). It’s not a perfect setup, but surprising how many things are spot on like soil warming from the house and seasonal variation. But I won’t know for sure until I build the darned thing!
Hard to tell, but I have readings inside, across a known insulation, and then outside at the foundation at the same level. That block should be R2, max, but the temperature gradients only make sense if that wall is closer to R8. So either they have foam or drain board on the outside of the wall, or stuffed foam/insulation into the block cavities, either of which could lead to that R value. I don’t have a better way to inspect those walls. There are other indicators the house was over-built too, like glue and screwed drywall, oversized joists for the span, thicker sheathing on the roof and outer walls. I really lucked out with this one.
My floor is 4" or so of poured concrete over compacted gravel. I drilled a 1/4" hole to get an under-slab temperature and could tell when I got through concrete, but stone dust was still coming out. So I don’t think there’s any foam underneath the slab, but again, no way to be sure.
I’ve never heard of doing foam under a slab. You have drain pipes and other things and there’s no point to having that insulated anyway. In colder areas, it’s not uncommon to have extruded polystyrene against the exterior basement walls. My guess is that you don’t have that either, since you’re not in the northeast and VA just isn’t that frigid. Your plan sounds reasonable. I don’t know the dif in R value between extruded poly and rock wool, but I’d look at that. The poly is easy to work with and it’s also a moisture barrier. And I’d get a small AC from Home Depot just in case you need it on some freakishly hot days. I had a brownstone and the basement walls were basically just piled up boulders with some mortar. On the other side was my neighbor’s basement. That wall was steady. But we were three feet above grade, not entirely subterranean, which sounds like your situation. I spent $100 on a little AC and we were fine in the cellar. Good luck.
Well if you have something like styrofoam tarred to the concrete walls, and [dry*] crushed rock [rather than bedrock] beneath the floor slab, then it will be more difficult for heat to flow into or out of your basement.
If the basement is hot, and the soil is cold, then it will take longer for the basement to cool.
If the basement is cold, and the soil is hot, then it will take longer for the basement to heat.
*My guess would be that if the crushed rock were inundated in water [rather than air], then it would tend to act a little more like a conductor [rather than like an insulator].
The other thing which can help tremendously is some ventilation in your attic.
If you could get two small screened windows up there, and open them [even just a few inches], then it would help enormously in bringing the temperature from maybe 140F back down to more like 100F.
The house wants to breath, and if it’s completely airtight, then all that superheated air has nowhere to go.
It’s as though the entire house is holding its breath, and turning red [and if you shoot the house with an infrared camera, then you’ll literally see the house burning].
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