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The heart of every wine cellar is the cooling unit but you might ask
“Which one should I choose?” Rest assured we can answer all your questions to ensure you receive the cooling unit best suited for your needs. The most important function of a cooling unit is to balance both temperature and humidity within the cellar, but other choices such as noise level and appearance may be important as well. We offer three types of cooling units: through-the-wall systems, split systems and air handler systems in a variety of sizes, styles and models.
Below is a collection of general information compiled by our knowledgeable staff to help you understand wine cellar construction in regards to proper cooling and humidity. You will find this information useful in terms of choosing the proper cooling unit to best suit your wine cellar’s needs. As always, feel free to speak with a representative at any point in time for further assistance by calling us.
Ideal Wine Cellar Conditions
Most experts recommend an average temperature of 55 degrees Fahrenheit for all wine storage. Cooler temperatures won’t damage your wine but will slow its development. A temperature of 65 degrees or more will have a negative effect on wine the longer it’s stored. The ideal humidity in your wine cellar should be 60-70% but anything over 50% is acceptable. High humidity, 80% or more, may cause mold to form on corks and bottles. In addition, ideal long-term wine storage should avoid heat, direct light and vibration.
Relative Humidity Presentation
This is a fairly complex subject and is based on the study of psychrometrics. While the word may be fun to say, the topic is a real headache. In short, relative humidity is calculated from a fraction, where the numerator is the amount of moisture in the air and the denominator is the maximum amount of moisture the air is capable of holding at its current temperature. This fraction is divided and multiplied by 100 to give the answer as a percentage. For a given amount of absolute moisture in the air the relative humidity will vary according to the temperature. The warmer the air the lower the relative humidity.
As a simple way to illustrate this phenomena imagine a clear, sealed box. Inside the box is a thermometer and a hygrometer (a device to measure relative humidity). When the box is sealed the thermometer reads 75° F and the hygrometer reads 50%. Now, place the box in a large walk-in refrigerator. (Remember that it’s sealed, no air or moisture can leave or enter the box.) As the temperature begins to drop the relative humidity will rise. When the temperature reaches 55° F the relative humidity will be 100% and the box will begin to fog up as moisture condenses on the walls. This is because colder air cannot hold as much moisture as warm air; therefore, the bottom of the fraction has become smaller and the percent relative humidity goes up. If the box is removed from the refrigerator and allowed to return to 75° F the moisture will re-evaporate and the relative humidity will return to 50%. Air conditioners and refrigeration units are designed to chill the air to a very low temperature as it passes through the unit. This removes as much moisture as possible for the comfort of people or the prevention of ice formation. If these systems were used in a well-sealed enclosure the relative humidity would be reduced to an extremely low level, very bad for wine. Breezaire cooling units are designed to chill the air only enough to remove the excess moisture, leaving enough moisture to keep the wine healthy.
In the wine cellar, desired conditions are generally around 55° F and 50% to 75% relative humidity. If the cellar is closed and the cooling unit is originally turned on when conditions are at 75°F and 50% relative humidity it will be necessary to not only cool the cellar but to remove some moisture. If moisture were not removed the relative humidity would reach 100%, mold and mildew would form on the bottles and walls and labels would fall off. Additionally, if warm moist air infiltrates into the cellar, the excess moisture must be removed or the relative humidity will rise to unacceptable levels. The cooling unit will be overworked and the excess water could overflow from the unit, making a mess.
Stratification – How a Wine Cellar Warms Up and Cools Down
Most people never think about how a room warms up or cools down, but again it is more complex than most realize. Warmer air rises and cooler air sinks. Old southern homes were built with tall ceilings where the warmest air would rise up above the people. Old homes in the north were built with lower ceilings to keep the warm air at people level. Both are based on the fact that a room warms from the top down and cools from the bottom up. It changes temperature by way of stratification. The top of the room will always be warmer than the bottom. So, how does this happen? Most heat enters the cellar through the various surfaces (floor, ceiling, walls, door …etc.) Molecules of air which are in contact with a surface are warmed up, become lighter than the surrounding molecules and rise to the top of the cellar. These warmer molecules all gather at the top of the cellar making a warm layer against the ceiling. As more and more molecules are warmed and rise upward this warm layer grows down the room. Meanwhile the lower portion of the cellar, under the warm layer, remains at a very stable colder temperature. A thin “stratification” layer that moves down the room when the cooling unit is off and up when the unit is cooling separates the upper warm air layer and the lower cold air.