Temperature
Ideally, the interior of a wine cellar is cool and breezy. At the same time, you want to avoid too much mold and moisture building up in your cellar. This may be harder in naturally humid areas. While your wines mature, or after they are ready and you are waiting to enjoy them, the temperature and humidity of your cellar should remain constant. Temperature extremes can harm the wine. Hot temperatures can spoil the bouquet and taste of your wine, while overly cold temperatures will keep it from properly fermenting. An ideal temperature is around 60 degrees with a humidity in the upper 60% range. While having a little fluctuation is alright, you want to make sure that there are no rapid fluctuations. Essentially what you are looking for is dark, cool and moist.
Humidity
The room you choose to make a wine cellar should not be built with drywall. Your new wine cellar has different needs than, say, your bedroom. Wine cellars are typically dark and cold places, with a fair amount of darkness. These conditions are conducive to excessive mold, which will ruin your drywall. It is advisable to use a heavier type of drywall usually referred to as Green board. This is the type of walling usually used behind showers, or near damp areas. green board’s density allows it to withstand excessive moisture.