Custom-building a cellar becomes cost efficient if you plan to store 1,000 or so bottles. That’s because the same chiller used in an 800-bottle wine cabinet can cool a 1,500 bottle walk-in cellar. The rest of the materials—2x 4-inch or 2×6-inch framing, a plastic vapor barrier, insulation, wine racks, and insulated doors—can be purchased relatively inexpensively.
Many northern hemisphere residents who have homes with basements have an ideal location for a walk-in cellar. These can often be passive cellars with no additional cooling required. If the open room temperature in the basement is in the range of 55–68ºF a passive cellar could well be a workable option.
… The electronic book “How To Build A Wine Cellar” contains full instructions for building your own wine cellar.