After converting their under-the-stairs closet into a wine cellar that holds 350 bottles— and patenting a rack system—Carlos and Kristi Davalos launched Closet Wine Cellars (closetwinecellars.com). Their tips for DIY:
Climate Control Install a small cooling unit, like one from koolspace.com.
Flooring Lay porcelain tile, slate or limestone to maintain a constant low temperature.
Lighting Use low-watt lighting (40 to 60 watts): Even a single bulb can heat up a small space.
Door Include thermal-pane glass in the door so guests can peek inside.