Photo credit: Sylvain Côté
Photo credit: Sylvain Côté
The very first rule is that these natural wine cellars are not for the finicky customer or the guy who wants to be in complete control of the temperature and humidity level to a precise standard. You’re a bit less in control with a naturally cooled cellar. That said, there’s no doubt in my mind that these are better designed, better thought-out and better built cellars than conventional ones. They are free, as free from energy bills and from cooling equipment breakdowns, noise pollution and power outages. They also are carbon footprint-free as well.
To make a passive wine cellar, you first need a basement. Using a corner of your foundation here is a must because you need two exterior walls for ideal cellar temperature. These two walls, along with the floor, are essentially your cooling devices. They should be as dry as possible so if your home is not fairly new, you may have to address excessive moisture or perhaps even water issues.
You must also consider the grade on the outside. How deep in the ground is the basement, meaning how high or how low is the grade outside? The deeper, the better. At a certain depth, which varies depending on the season and where you live, the ground is always around 55 F, which is the ideal temperature connoisseurs want to store their wine. Southern-facing exposures can be an issue in summertime due to heat gain through the foundations. That side should be shaded by planting shrubs. Even if the cellar is well-insulated, the sun hitting the foundation will still affect the interior temperature.
Speaking of insulation, it is your most crucial step of this whole process. Start with the foundation insulation where it is most vulnerable to variable temperature fluctuations. Here we use 2-inch-high density rigid insulation boards glued right on the concrete. This insulation needs to go further down the grade line by roughly 2 feet. It is important to remember that you are cooling your cellar mainly via these walls, so you don’t want it too far down. The next big thing is to insulate the framed walls. These walls should be approximately 6-inches thick at the most and staggered, double-framed and really well insulated. A few inches of closed-cell spray foam here will do. The rim boards and the ceiling should be addressed in the same manner as well. As far as ventilation, if you are concerned with air quality, then I would recommend installing an energy recovery ventilator.
We are now ready for the finishing touches. We like to use French glass doors so you can see into the racks and your bottle collection. For these, we prefer to use a double-pane, 12 or 15 lite slab and make it weather tight, just like an exterior door would be treated. You should do your lighting with LEDs to minimize the heat gain. You don't need anything too bright; LEDs are cool and use very little energy at around 9 watts per bulb. The floor could be left as concrete. If you’re the artist type, you could acid stain it and then seal it for a more creative finish (this process is a nice alternative because it is inexpensive). Alternatively, you could install limestone or flagstone tiles. If you have to pour a new concrete slab, you then have a new opportunity and the option of stamping the concrete while it’s still wet.
We prefer to design and fabricate our own racks made out of antique wood, such as old posts and beams that we sometimes purchase at specialty suppliers or reclaim the lumber ourselves from local old barns, usually at a lesser cost. We then clean it up and make our own wine racks from scratch. For the lack of reclaimed lumber you can use plain pine 2 by 4s, rip them in half on the flat side and finish them with an antique stain (as we did in my own cellar, the “Vintage Cellar”). Done right, and under the proper dimmed lighting, it looks like antique wood. Because too much of a good thing is usually a bad thing, I like to break up all that wood with a bit of stones (after all, we are below grade) where we basically used the unusable space in the corners to erect two stone pillars.