Exactly. I can’t imagine that you’d want it at one of the daylight settings, though. They come across as very cold and blue.
An update on my passive cellar. It’s mostly subgrade (18-24" above ground on the outside) in the Hudson Valley at 800 feet elevation, where the nights tend to be cool, and it’s on a northwest corner. That’s all good. Still, there’s more temperature fluctuation than I expected, and it’s been very rainy, so outside temperatures haven’t really put it to the test.
A few lessons:
You may need more insulation that you think:
Gold calculates that, depending on the temperature of the ground beneath the floor, you’ll need from R-38 to R-60 on the other surfaces. Looks like he may be right. R-60 is hard to achieve even with spray foam. You need very deep wall and ceiling cavities, and this wasn’t going to be a big enough job to call in a spray crew. So I went with the most I could fit in.
Ceiling, facing main floor: R-44 = 7" R-31 fiberglass batt between 2x8 joists, covered with 2" R-13 R-Max closed-cell, foil-covered foam board
Walls facing rest of basement: R-34 = 5.5" R-21 fiberglass between 2x6 studs covered with 2" R-13 R-Max board
Foundation walls: Probably R-10; not sure because it was sheetrocked over when I bought the place, but the rest of the basement has 2" foiled foam board.
The rest of the basement is staying in the high 60s.
To my surprise, the wine room has fluctuated between 59F and 61F, getting warmer in the afternoons, then cooling overnight and through the morning, so the room isn’t that well isolated from the outside temperature. I figured with R-44 and R-34, it would be more steady.
An infrared temperature gun/sensor is super helpful:
I got one for about $35 at Home Depot. You just point and hold the trigger for a couple of seconds and it tells you what the surface temperature.
From this I learned that the floor temperature runs from 55F along the foundation walls and in the center of the room to 57+F closer to the rest of the basement. The walls are between 57F and 58F, both along the foundation and on the basement-facing surfaces. It appears, therefore, that the foundation floor is transmitting heat from the rest of the basement into the wine area. (Basement floor temps are running in the mid-60s.)
I’ll try to reduce that. When I install cabinets on the outside of the cellar wall in the basement, I will put insulation board under the cabinets to insulate that part of the floor from the ambient temperature.
The big surprise with the temp gun was that the interior surface temperature of the door (a standard insulated exterior door from Home Depot of unknown R value) is only about 0.5 degree higher than the adjacent walls. I figured that would be the weak point and I’d planned to install a double door or cover the door with foam board. I may be able to save myself some hassle.
Don’t assume the foundation walls will cool your cellar.
That was one of the most important things I read in Gold. He says that ground temperatures in the Northeast can run in the mid-60s in the summer time even five feet down. That seems to be borne out by my interior wall temps of 57-58. The west wall is about a degree warmer than the north wall. I took my chances by not tearing out the existing sheetrock to add insulation.
I may put some insulation board on the outside of the foundation on the west and build a little planter around it to try to reduce the temperature of the concrete. That would shade the wall and, hopefully, cool that foundation wall substantially.
I’m not going to freak out if the cellar ends up running at 60F over the summers. It was in the low 50s in the winter. I think that will be fine for the wine, and I’m happy not to have to resort to mechanical cooling.
Excellent report John, thank you!
The tip about the heat gun is a good one. I did not realize they were that inexpensive. I may have to pick one up to test my own passive cellar.
I started loading up my passive cellar at the end of last summer. I am quite interested to seeing what happens when the heat of the summer comes.
Like you, I am a bit surprised by the changes already. I am not really seeing that much in-day variation. But, in the past 30 days, the temperature has risen from about 53.5 to almost 57. I was hoping it it would be a little more gradual, and not sure what that portends for the summer.
I am interested to find out if you come up with a method to keep the basement floor heat from seeping into the cellar…
If it is 60 in summer your job is done and you can crack open the champagne!
Do you have wine in there already? (sorry, I haven’t read all you’ve written.) That will keep the temperature more stable (to state the obvious…)
If you worry about temperature fluctuations over the year, you could always let some heat in during the winter! 60 degrees year-round would be fine IMHO.
50 degrees all year and your big wines might not be ready in your lifetime!
Hard to do without building an entire floor over the slab! I think the best you can do it put in some subflooring and flooring with a bit of R-value. The good thing is that the ground under the slab is pretty close to the temperature you want anyway.
I used a subfloor of DriCore (you can find at home depot) and cork flooring above that. The theoretical r-value is about 3. But only took up about 2 inches, and provides a moisture barrier (although in center of basement that’s not a major issue unless I have a disastrous flood).
I understand that some people use them for cooking, which makes that $35 an even better value!
This would really just be a minor change at the margins, but it’s easy to achieve. I’ll try to work in another 1" R-Max (R-6.5) board behind the cabinets, too.
I’ll be happy if it fluctuates between 50F and 60F over the course of the year. My concern is that summer hasn’t really arrived yet and the basement is running at about 67+F and the wine room is a tad over 60. I’m very surprised at the fluctuation given all the insulation and that relatively small temperature differential.
In addition to the boiler down there (only for hot water in the summer), I suspect a lot of the heat buildup in the unenclosed basement is from four smallish windows. I plan to cut plywood to cover them. I’ll put handles on the plywood so I can pull off the covers when I want daylight down there.
I have maybe 10 cases in there now, so not enough to create any great thermal mass. When I have 50+, that should help.
I trust you’re talking about adding flooring/insulation on the areas outside your cellar. That’s what I’m considering with the cabinets on the outside.
Just so no one is confused. With a passive cellar, you don’t want to insulate the floor inside the wine room at all because that’s the primary cooling surface. The walls are, at best, neutral and will likely be above 55F, as mine are.
No, I was talking about in-cellar flooring, but my cellar isn’t passive.
For passive I wonder how effective insulating the floor outside the basement is when the ground/slab is effectively an infinite heat/cool sink.
Appreciate the clarification John. I agree: DO NOT insulate or add anything to the floor inside the passive cellar.
It’s probably not that effective, but the outside floor immediately adjacent to the wine room is substantially cooler than other parts of the basement floor, according to my temp gun. Gold says that concrete is a reasonably good conductor, so I’m assuming the outside perimeter of the wine room is somewhat cooled by the floor inside and the inside perimeter is somewhat warmed by the floor outside. If I can insulate an 18"-24" band of floor on the warmest bordering floor area outside, under the cabinets, it might reduce the transmission of heat into the wine room a little. And it’s easy to do.
None of this theorizing would be possible without that infrared gun!
^ That’s good data!
Cool info. I’m looking at this myself right now actually. So should I leave the floor bare concrete, or is it ok to put some type of flooring? Right now there is a rubber type flooring in there. How much difference does it make?
In a passive cellar if the floor is adding too much heat then you are toast. You’ll simply need to add active cooling in that scenario. Insulating the floor in a passive cellar is the opposite of what you want to do. The floor is your cooling so if that is too warm you simply must add active cooling.
Active cellars you can pretty much do what you want with the floor. I’ve seen active cellars with insulated floors many times but most don’t bother. It raises the floor which is a bit of a PITA when going in and out carrying heavy items like wine.
You need to read the previous posts, mine and and John S’s.
The floor is the only surface likely to be much below 60F, unless your exterior walls are entirely, and well, below ground. So you don’t want to cover the concrete floor in any way. In a passive cellar, it is your only ally.
I am with James, it appears that your cellar is preforming admirably. My passive cellar is in my crawl space in Alaska and I get approximately the same temperature ranges that you are seeing. I have had my cellar for 20 years and I have noticed no ill effects from small daily fluctuation in temperature. I actually have greater fluctuation in the winter because there is heat ducting in the crawl space. Of course the wine temperature fluctuation is less than the air temperature fluctuation.
As I said, I’m not sweating it. I stored wine in an uninsulated basement storeroom in San Francisco for 10 years, where temperatures did get over 70 in September and October (the warmest months in SF). I still have wines from the 80s that I stored there and have never seen any signs of advanced age.
There are radiator lines around the outside edge of my new cellar, and a high-BTU radiator and fan under the kitchen sink immediately above. I’ve put extra insulation around them, but I figure that when the heat’s on a lot, it wouldn’t be bad if a little penetrated the cellar, since the rest of the basement was holding around 50F across the winter.
John, I don’t think it’s an issue if your cellar gets to low to mid 60s for a few months.
I think the average temperature over the year is the key factor as long as your cellar never gets too hot (say over 70) or fluctuates wildly.
Does anyone else agree with my [Edit: not exactly radical] theory about wine development being mostly related to average storage temperature (given no extremes nor rapid fluctuation)? For example 60±5% ?
That’s my hunch. But, so far as I know, there’s virtually no research on this.
The only relevant thing I’ve ever seen was some charts about how brett multiplies rapidly over some temperature (high 60Fs, as I recall). That illustrates that there is not a single line for development. Oxidation may have a different temperature curve than polymerization, which may be different than brett and VA growth.