The primary function of a wine shelf is preservation. Ensure the design allows for horizontal storage, which keeps the cork moist and prevents oxidation. The spacing between tiers should accommodate various bottle shapes, including Bordeaux, Burgundy, and Champagne bottles (typically 3.5 to 4 inches of clearance). For long-term storage, look for open-air designs that promote proper ventilation to prevent mold growth on labels, and ensure the finish is low-VOC (Volatile Organic Compounds) to avoid chemical odors tainting the wine through the cork.