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Why regulating humidity is a balancing act for prestige and classic car storage

5 min read
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For any prestige or classic car owner, rust, mould and corrosion will cause sleepless nights while their treasured vehicle is in storage. The older a car gets, the more precious it becomes, and the more susceptible it is to unregulated humidity levels.

In this article, you’ll discover some of the hidden dangers of fluctuating moisture levels in the atmosphere, and why every automotive enthusiast can rest easy with their vehicle in the safe hands of a high-quality dehumidifier.

Why is humidity such an issue?

Even in pristine garages with the most fastidious mechanics on-hand, moisture in the air can cause extensive damage to vehicles. This could be because of outside temperatures, heating or air conditioning systems, cars returning from a drive in the rain, or people coming and going.

With an ever-changing environment, damage to interiors, exteriors and mechanical parts is inevitable. That’s why maintaining optimum relative humidity levels is a key factor in keeping a garage in check.

Relative humidity (RH) is the amount of moisture that the air can hold at its current temperature. Because warm air can hold more moisture than cold air, an environment’s relative humidity percentage is not a direct measure of the amount of water vapour present. For example, there will be more moisture in the air at 50% RH when the temperature is 25°C than there would be at 10°C.

Sudden changes in temperature will alter RH levels dramatically. When the air rapidly cools, RH levels can reach 100%, or dew point, causing the water vapour to condense. Any material that’s colder than the dew point of the surrounding air will be susceptible to condensation.

When RH levels are too high

  • Rust and metal corrodes at a faster rate

  • Musty odours develop in interiors

  • Wood paneling can swell or rot

  • Engine performance deteriorates

To create a safe environment for your piece of automotive history, RH levels should be kept below 60%

For some context, the table below shows how fast high RH levels can corrode the steel components of a vehicle.

Corrosion of steel chart

How to keep humidity under control

When garages and storage facilities notice condensation, heating is often the first solution they turn to. Unfortunately, this will only increase the amount of moisture that the air can hold. Aside from adding to expensive energy bills, there is a greater risk of water droplets settling on surfaces when the temperature drops.

Unlike heating, dehumidifiers will circulate air throughout a space and physically remove the moisture as it flows through the system. In colder climates or during winter months, a Calorex system can convert 2.5 times the amount of energy it uses into usable heat. Compared to traditional heat and ventilation, a garage or storage facility could see costs savings of up to 75%.

Find the best dehumidifier for your facility

The first thing to consider before choosing a dehumidifier is the size of your facility. Calorex supply bespoke systems for everything from private one-car garages to multi-level storage facilities.

The table below is a quick reference for common garage sizes, but you may also need to make the following adjustments depending on your facility:

  • For unsealed buildings (e.g. spaces in constant use or with poorly fitting doors), halve the building volumes per unit selection.

  • For buildings extremely exposed but well sealed, divide building volume per unit by 1.6.

Garage size (m³)


Up to 150m³

DH 30

Up to 350m³

DH 60

Up to 1000m³

DH 150

*Larger units are available

With over 20 years of experience developing dehumidifiers specifically for prestige and classic cars, Calorex dehumidifiers can be optimised for any sized collection or storage facility. To learn more about the options available, don’t hesitate to get in touch with our team.

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