How should I insulate a 10 x 14-foot basement space for a wine cellar I’m building?

How should I insulate a 10 x 14-foot basement space for a wine cellar I’m building? Three walls face soil and a rec room is outside the fourth. All walls are currently insulated. The door is hollow wood and I’m aiming for a 13ºC temperature year round.

As you probably already know, storing wines optimally involves not only the correct temperature, but also a stable temperature. It’s this need for stability that ultimately leads to the need for some kind of energy input for your wine cellar. Seasonal outdoor temperatures vary so much here in Canada that you’ll either need to add a little heat in the winter or a little cooling action in the summer, depending on the insulation strategy you follow. Let me explain how all this works in a real-world example.

I use my unheated, stone basement as a root cellar and its masonry walls are completely uninsulated. Even in the hottest summer weather, temperatures never get warmer than 15ºC. That said, temperatures in the basement regularly sink to 2ºC or 3ºC during the coldest winter weather. That’s ideal for storing root vegetables, but too cold for wines. Adding insulation to the exterior walls of your basement cellar will boost wintertime temperatures closer to ideal, but it also means that summertime temps will probably be too warm.

If you’ve got the patience, your best option now is to watch temperatures as winter unfolds. Plot cellar and outdoor temperatures on a graph until the end of spring and you’ll learn a lot. I suspect that your best option will be to remove the insulation on exterior walls, adding the little bit of heat necessary to bring the temperatures up during winter. The other alternative is to retain the insulation and use electricity to cool the cellar in summer.

Either way, you’ll benefit by replacing that hollow wooden door you’ve got now with an insulated door meant for exterior use. These seal well, and that’s important. It’s always an advantage to keep heated basement air out of your wine cellar.