Cellar Temperature Stability

When we moved house 9 years ago, I took the opportunity to design and have built my ideal cellar, and insisted on using spray foam insulation as one wall was an exterior wall, plus you can lose a lot of heat through the ceiling and floors. Normal exterior R value is R-22 but the closed cell spray foam kicks that up a bunch. With 4" of closed cell you get R- 28 as opposed to R-20 with fibreglass batts of the same thickness.

Today I had the first opportunity to test it out properly. My fridge was at 52 F., and the fridge freezer was at 25 F. when the power came back on - normal is 40 F, fridge and 0 F for freezer.

The upright freezer was at - 10 F. - normal setting is -23 F

My wine cellar was still at 55 F (13 C.) after being turned off for 8 hours The normal temp in there is....55 f (13 C.)!

I'm posting this as information to anyone wanting to build a cellar and deciding on what sort of insulation to use. Bear in mind that there is a lot of thermal inertia with the wine bottles and the temp would have risen more quickly if the cellar had been empty
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Yeah, closed cell spray foam is great stuff. We used it on some walls of our passive cellar, which has shown almost zero diurnal variation after a full year, and moves very slowly between a low of 54 and a high of 64 over the course of the year, which is about what I hoped for, and perfectly adequate for my purposes.

Sounds like my first cellar - in a room half below ground and I turned off the old style radiator completely. It rose to around 65 F in summer and dropped to 50 something in winter, which was just fine. I 'made' the racks by buying quite a lot of the old wood and wire holders for glass milk bottles - the sort the milk man used to drive around with. I just stacked them on their sides about 7 high and there was never any issue of teetering when the weight was in them.