Climate Controls for Wine Storage

Like most perishable items, the quality (and taste) of wine is strongly influenced by the basic environmental conditions in which it is kept. Unlike most perishable items, wine tends to be stored over long periods, and so its quality and taste can be affected by the most minor variations in that environment. As such, the standards for wine storage tend to be higher than for most other cold storage applications.

Creating the ideal climate for storing, preserving and maturing fine wine requires the following:

an amenable location;

an extensive retrofit of the base building;

an advanced (zoned) cooling system strategy;

proper humidification and dehumidification controls;

a good power supply, equipment redundancy and regular maintenance;

professional monitoring and oversight of the cellar environment.

The Location

Professional cellaring requires a suitable location. The base building must have specific thermal and design characteristics. The composition, configuration, and design of the cellar perimeter are all critical factors when evaluating whether the proposed location will ever be capable of providing long-term temperature stability, humidity control and security. Then in preparation for the retrofit, the building's owner must also be amenable to having the interior of their building stripped completely down - to a raw and unfinished state.

Proper base level: Provided there is good drainage, basement level space is definitely preferred. Ground level cellars are possible provided there is no infrastructure or open space located below the cellar, all perimeter walls are massively insulated, and there is a back-up generator installed for the climate control system. Locating the cellar on solid ground versus open space is absolutely critical. Fine Wine Reserve's cellar is ideally situated in sublevel space eight feet below the ground. The cellar floor is concrete slab and sits on undisturbed soil.

Proper external shell: The majority (70%) of the perimeter of the Fine Wine Reserve cellar is in fact enclosed within another larger structure, and that larger structure is situated below ground. This layout provides excellent buffering from direct sunlight, temperature extremes, and severe weather events - all of which cause drastic thermal variability on what is a very large cellar perimeter. At the Fine Wine Reserve there is an even and constant heat load on the majority of the walls which significantly reduces the potential for temperature fluctuations in the first place. Although this type of configuration is fairly easy to find, finding one that meets all the other design requirements including perimeter security is difficult. Simple brick or drywall partition walls are not acceptable due to the ease at which these walls can be penetrated. Our perimeter walls, interior or otherwise are all high security - composed of 22 to 48 inches of solid brick and masonry, plus a custom-designed portion (insulation and vapour barrier) that adds another foot of thickness.

Proper ceiling heights: Too low and air flow from the evaporators is restricted and temperature stability lost. Too high, and the large air to liquid ratio reduces temperature stability and blackout protection levels. Proper ceiling height partly depends on how high the wine is to be stacked in the cellar. Our stacking height is 8 to 10 feet. Optimal ceiling height for that storage configuration is 12 feet, and that is what we have at the Fine Wine Reserve.

Other non-engineering-related location factors also come into play such as lease term length. Professional cellaring providers must either own the building or be able to negotiate a solid, long-term lease with a large corporate landlord. It's too risky to deal with "small landlords" due to the associated security concerns and lease stability. Should the landlord sell the building or otherwise create a problem with the site, expensive retrofitting makes having to relocate a professional cellar an unfeasible proposition. (The Fine Wine Reserve's property is under a long term lease with options to renew with a large public corporation operating a publicly traded REIT.) If your storage provider can afford to relocate his cellar, it is a good indication that they are not investing the capital required to convert basic warehouse space into a professional wine cellar.

After an 18 month search and 107 property inspections, the Fine Wine Reserve found its home. Once the location was determined to meet the basic design criteria, engineers, architects and contractors were sent in to further investigate the building envelope. Site surveys and heat load calculations were conducted. A comprehensive plan to construct, renovate, and retrofit the space was proposed and mechanical and architectural drawings produced. A budget was drawn up, and the costs determined to be feasible. Only then was the prospective space deemed suitable for professional cellaring.

The Retrofit

Having identified the proper location, an extensive retrofit is still required. No warehouse or building (fur storage or otherwise), comes ready-made for the wine storage application. Over a seven month construction period, $600,000 was invested into retrofitting our space to bring it up to professional cellaring standards.

Within the already bunker-like structure, our first step was to "build another building within the building". This was to upgrade the structure's insulating and humidity retention performance and achieve the standards of temperature stability and humidity control one should expect from a professional cellar. Leaving a 2 inch air barrier, 6 inch stud walls were erected around the entire inside perimeter of the stone walls. The walls were then filled with 5.5" of mineral wool insulation. We then wrapped the entire facility with 6 mil vapour barrier, and a half inch of waterboard. Total R-value of our interior perimeter walls now exceeds 25.

The ceiling is made up of heavy timber planks laid side by side to achieve 6+ inches in total thickness. To the underside of this, we added a continuous vapour barrier, and a three inch layer of mineral wool insulation with a black matt facing. Total R-value of the ceiling now exceeds 20.

Steel I-beams supporting the ceiling were wrapped with three inches of mineral wool insulation, and then framed with waterboard. We did this to prevent even the slightest transfer of heat or cold along the beams from the exterior of the building which could possibly upset cellar temperature stability.

Partition walls between the cellar and administrative facilities (mechanical room, electrical room, security room, etc.) were also built six inches thick and insulated to R-20+ to maintain temperature stability in adjacent cellar areas.

Egress into the cellar area was separated from the non-climate-controlled zones by an air-lock or buffer zone so that on-going operations does not adversely affect temperature stability in the cellar.

All windows along the exterior perimeter wall and behind the cellar infrastructure were covered with three-quarter inch plywood, followed by 6 inches of concrete to increase security and temperature stability in the cellar.

The doors have an insulated core, heavily weather-stripped, and outfitted with state-of-the-art drop down seals at their base to prevent the transfer of air in and out of the cellar. Doors have heavy-duty LCN closer mechanisms, closers used only in the most rugged applications. Where required, automatic closers/openers and door ajar alarm systems are employed. All these steps are taken to reduce the effect that operations have on the integrity of the barriers (thermal, vapour, and security) that protect our cellar.

Facility lighting is low voltage (9 or 13 watts), low lumens, and virtually non-heat generating. Half the cellar lighting is designed to shut down automatically when it senses the area is vacant. This reduces temperature stratification and increases temperature stability. Floor to ceiling temperatures vary less than 1.5°F at the Fine Wine Reserve even during heat wave conditions.

Although time consuming and expensive to complete, the renovated facility is now a highly "insulated box" providing precise, stable temperatures and excellent blackout protection. Temperature is maintained within a very narrow range (0.5°F) both diurnally and seasonally. This level of temperature stability is the most difficult thing to achieve and the Holy Grail for the wine storage provider.

Cooling System Strategy (Zoned Cooling)

Long-term aging of wine requires a unique environmental condition. It is a low temperature, high humidity application. Above all, the air temperature must not be allowed to fluctuate, but be maintained within a very narrow range. Temperature stability is perhaps the most important factor in long-term wine cellaring. It is a difficult condition to provide, particularly on a commercial scale. It can only be achieved with a well designed climate control strategy.

The Fine Wine Reserve is kept at a constant 55°F (12.8°C) using seven independent cooling systems totalling over 60,000 BTU's or five tons of refrigeration. The entire system is computer controlled. Capacity or supply is 250% of the peak load, meaning we can maintain operating temperature using less than 1/3 of our equipment during heat wave conditions. This high margin of over capacity was installed on purpose. It is a necessary feature of the zoned cooling system strategy.

Zoned cooling is a technique in which a high number of smaller cooling units are used versus using a fewer number of large units. Using multiple smaller units ensures each individual area of the cellar only gets the cooling it needs. This strategy prevents any individual cooling unit from having to expel refrigerated air, which is lower than cellar temp, for more than a few minutes at a time. Facilities that do not employ zoned cooling will have units running on long cooling cycles. This will overcool all the wines located in areas adjacent to the unit as it works hard to cool the areas located far away from the unit. These same wines will then warm up between cooling cycles. It costs a great deal more to install a zoned cooling system, but is the only way to avoid wine temperature fluctuations, particularly in a commercial-sized cellaring facility.

Zoned cooling is a feature you will only find in the professional cellaring facility. Using a small number of large cooling units is standard operating procedure at less qualified cellaring facilities, such as at the fur storage or the basic cold storage warehouse. These facilities are designed for product that must only be kept below a certain maximum temperature, and how much the temperature fluctuates below that point is of no real concern. The best way to determine whether or not your provider is using a zoned cooling system is to divide the square footage of the cellar area by roughly 500 square feet. Assuming the units are properly sized (and that is a big assumption), the result should approximate the number of cooling units you see in the space.

Another advantage of the zoned cooling system is the large number of evaporator fans that we have operating in the cellar. We have seven such fans that run continuously (24/7), regardless of whether or not the cooling unit is actually in a cooling mode. With many fans running inside our cellar, the air is constantly moving. This keeps the cellar air homogenous and stable, and further improves our temperature stability standards. The Fine Wine Reserve's overall cooling system strategy means we can maintain cellar temperature within the extremely narrow range of 0.5°F.

Humidification & Dehumidification Control

A firm but pliable cork is the only thing preventing your wine from becoming oxidized and/or your bottles ending up with low ullage levels. The integrity or moistness of the cork is critical to the successful long-term storage of wines. Protecting the bottom half of the cork is simply a matter of making sure the wine stays in contact with the cork, and hence the requirement to store your bottles on their side or upside down. Protecting the top half of the cork comes down to proper humidity levels in the cellar. Acceptable levels are defined as being between 60% and 75% RH. Our facility is kept between 65% and 75% RH year round.

n warm southern climates, cellar humidity levels are usually high enough all year round without having to intervene. In temperate climates like Toronto, wintertime humidity levels in the cellar will be too low, unless the operator has some way of getting more moisture into the air. A surprising number of so-called professional cellars don't have any humidification systems at all. Some use steam based systems, but most of these upset temperature stability due to the high heat involved. We use an ultrasonic fogging system.

The fogging system is computer controlled and allows us to dial in whatever humidity level we desire. The fogger is set at 65% RH. When cellar humidity drops to 65% RH, a cloud of cool mist automatically evaporates throughout the cellar raising the humidity back to 70% RH before shutting off again. During the very coldest part of the winter, our fogger runs for about 60 minutes every three or four hours. Each cycle releases about eight litres of water into the air - this water being heated to about cellar temperature before release. This is a large amount of water, particularly when you take into account the fact that our cellar is completely wrapped in a vapour-barrier. Without humidity-retaining infrastructure, as is the case in most non-professional cellaring facilities, these systems would have to operate almost continuously to maintain 60%+ RH during the winter months. That scenario is unfeasible and one of the main reasons why facilities that have not gone through a proper retrofit don't bother with humidity control either. They just hope your corks will make it through a series of dry winters. Wintertime humidity levels at the Fine Wine Reserve are between 65% and 70% RH.

In the summer, the opposite effect takes place in the cellar. Cellar humidity levels spontaneously increase. Although humidity levels above 80% won't harm the wine or the cork, extremely high humidity can lead to condensation, mould and damage wine labels and the cellar. The effect of increasing summertime humidity levels is actually more pronounced in a professional cellar like ours. Professional cellars are so well insulated that there is a lower load on the cooling systems - systems which in fact help dry the air.

To mitigate high summertime humidity levels, we use a special air handling system. First the system draws in the moist cellar air to be "conditioned". The air is cooled down to near freezing, and the water (i.e. humidity) drained off. It then takes what is now dryer air and warms it back up to cellar temperature. Finally the dry cellar temp air is returned to the cellar. With this air handling system, we can maintain cellar humidity levels between 70% and 75% RH during the summer months, with 70% levels breached for only very brief periods (during extended heat wave events coupled with a lot of rain). Using the same air handling system, we can also flip a damper switch and perform the same process with fresh outside air. We can exchange 100% of the cellar air with fresh air in about 3 hours.

Power Supply, Equipment Redundancy and Maintenance

No matter how well designed the climate control systems, if the operator's power supply is unreliable and/or there is no redundancy built into system, then power outages and equipment failure will result in periods of temperature instability.

The majority of the Canadian population relies on electrical power supplied by an individual feed station. When there is a problem in the line or the feeder station itself, the result is a power outage. There are numerous ways that feed can be interrupted including power surges, lightening strikes, wind blowing a branch on a power line, car-utility pole collisions, and so on. As such, these routine power outages lasting a few hours (and up to a full day) can be quite frequent, even in very urban areas.

The Fine Wine Reserve does not experience these routine power outages. The cellar is located in an exclusive area of the downtown core that is part of a "power network". In the event of an interruption, the power feed instantaneously switches to an alternate feed in the network. The result is very reliable and stable power supply and reliability statistics for our address confirm that fact. Although catastrophic power outages lasting more than 24 hours have yet to occur at our location, should it happen, our power will be quickly restored in this heavily populated and economically important area of the country (i.e. the 2003 East Coast black-out lasted less than 24 hours in our area).

Should there be a lengthy power failure, the Fine Wine Reserve is optimally located and so well designed/insulated that two conditions would have to occur simultaneously before it would be considered a significant power interruption event: 1) the outage would have to occur during peak summer or winter conditions, conditions only experienced less than 8% of the time and, 2) the failure would have to exceed 4 or 5 days in length. We believe that the chances of ever being without power in downtown Toronto for that long is extremely remote.

Should there ever be a catastrophic power outage, those with wine at the Fine Wine Reserve will be very well served. Heat load calculations indicate that power outages of less than 4 or 5 days (and 7+ days during non peak conditions) will have virtually no effect on the Fine Wine Reserve. These calculations were confirmed by actual testing in 2005. All power was shut down to the cellar for a period of 24 hours. The test was conducted during peak conditions, at a time when the outside air temperature differed from the cellar by an extreme amount - by an average of 39°F (22°C) over the 24 hour period. At the end of the 24 hour period, the largest temperature fluctuation recorded in our cellar was less than one degree (0.9°F / 0.5°C). This test was also at a time when the cellar was at less than 30% capacity - meaning we did not benefit from the natural thermal retention effects of 100,000's of litres of 55°F wine we now have stored at the facility. The test was a clear demonstration that our location and cellar construction parameters are sound and that it provides an exceptionally high standard of protection for your wine.

Other than the actual design of the cellar itself, the ability of the wine storage provider to protect your wines long term (i.e. reliability) mainly depends on the equipment systems in place, the operator's maintenance practices, and management's emergency preparedness. The Fine Wine Reserve climate control systems are capable of supplying 250% of the peak load conditions, meaning we can maintain our environment using less than 1/3 of our equipment. This massive amount of over capacity provides plenty of equipment redundancy and an extra level of protection for your wines. Then, the Fine Wine Reserve has a signed contract with a professional HVAC company to perform bi-annual inspection and maintenance of our systems to keep that equipment running at peak performance. Even so, equipment will break down from time to time, and so we keep a good supply of critical spare parts on hand (e.g. motors, bearings, belts, etc), to ensure repairs are done without delay. Finally, management is cognizant that not everything can be controlled. These have been identified and a Catastrophic Event Plan drawn up to minimize the potential effects of such an event on their clients' inventory.

Monitoring and Oversight of the Cellar Environment

The Fine Wine Reserve provides around-the-clock supervision of the environmental conditions around your wines. Our staff inspects the cellar and its systems on a daily basis. But breakdowns are just as likely to happen when no one is around, so the daily check isn't enough at the professional cellaring facility. That's where our sophisticated remote monitoring systems step in. These systems continuously monitor cellar power supply and cellar temperature. Should conditions ever stray from certain pre-determined limits (high or low), or should the power supply ever fail, the system automatically notifies the alarm monitoring company and management, so immediate action can be taken.