Wine Cellar Cooling 101
At the heart of every wine cellar is the cooling unit. But you might ask, "which is right for me?" 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. IWA offers 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 knowledgable IWA staff to help you understand wine cellar construction regarding proper cooling and humidity. You will find this information useful for choosing the proper cooling unit to best suit your wine cellar's needs.
And as always, feel free to contact us via email or speak with a representative by calling us at 1-800-527-4072.
Ideal Wine Cellar Conditions
Most experts recommend an average temperature of 55° Fahrenheit for all wine storage. Cooler temperatures won't damage your wine but will slow its development. A temperature of 70°F 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 may cause mold to form on corks and bottles. In addition, ideal long-term wine storage should avoid heat, direct light and vibration.
The Concept of Relative Humidity
Relative humidity is calculated as 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. 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). Inside the sealed box, 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 increase. 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. 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 vs Wine Cooling Units
Air conditioners are designed to chill the air AND remove moisture for the comfort of people. Most HVAC systems are designed to maintain approximately 20% relative humidity. If AC systems are used in well-sealed enclosures, the relative humidity will be reduced below ideal levels for proper wine storage and agin.
In contrast, wine cooling units are designed to chill the air WITHOUT stripping moisture from the air (below 70%). Assuming the cellar is well-sealed, when conditions are at 75°F and 30% relative humidity, when the cooling unit is turned on, the relative humidity will rise to 60% when temperatures fall to 55°F inside the cellar assuming the cooling unit doesn't strip out any moisture.
Excess Moisture / Unsealed Wine Cellars
When ambient humidity conditions are high, infiltration of ambient air into the wine cellar will increase humidity conditions in the cellar. If excess moisture is not removed, the relative humidity will rise, causing condensation to occur and mold and mildew to form on the bottles, labels and walls in the wine cellar. Under these conditions, the cooling unit will try to remove the excess moisture from the wine cellar. However, this process of condensing moisture will reduce the cooling unit's ability to generate cold air, and may cause the cooling unit be overworked. In addition, the excess water must be managed or it may cause water damage inside or outside the cellar.
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.
Types of Cooling Systems
Self-Contained, Through-the-Wall Cooling Units
Through-the-wall cooling units are self-contained, fully charged and ready to use out of the box. These cooling units are designed to be installed through a hole in the wall, with the front of the cooling unit inside the wine cellar and the rear of the unit outside the wine cellar in a space that is large enough to provide sufficient ventilation.
Some self-contained units can be partially or fully ducted; however, ducting may require auxilary fans and manufacturer guidelines should be consulted for proper installation.
Through-the-wall cooling units are the most affordable and easiest to install; however, the noise from the unit cannot be separated and will reside at the rear of the cooling unit. Available in sizes ranging from 100 to 2000 cubic feet.
Split Cooling Systems
Split cooling systems separate the evaporator and condensing units, allowing the placement of the condensing unit in a remote indoor or outdoor location. Once installed, these cooling systems are quieter and less intrusive because the condensing unit can be located anywhere you choose.
Split cooling systems must be installed and charged by a licensed HVAC/R technician. Available in sizes ranging from 100 to 2000 cubic feet.
Air Handler (Ducted) Systems
Air Handler cooling sytems are designed to be remotely located for partial or complete ducting, and are suitable for medium to large rooms in residential as well as commercial settings. Unlike other cooling systems, Air Handler systems offer heating options for cooler climates as well as humidification options for dry climates. The discreet air distribution provides a quiet atmosphere accompanied by an attractive, easily disguised appearance.
Some Air Handler cooling systems offer a choice of configurations, include vertical and horizontal orientations as well as self-contained and split systems.
Air Handler split systems must be installed by a licensed HVAC/R technician. Self-contained systems do not require a licensed HVAC/R technician for installation. Available in sizes ranging from 1000 to 2500 cubic feet.
Still have questions about cooling units?
Call us anytime at (800) 527-4072 to speak with an IWA wine cellar specialist.