Car humidity control: Why it’s essential long term protection

Some car owners can be forgiven for neglecting such things. After all, humidity is something that is usually out of sight, out of mind- and if you’re someone who replaces their vehicle with a brand new car every few years, you probably won’t have to deal with the humidity damage that is likely to occur down the line.

However, if you have a classic car in your collection or want to maintain the value of a big investment, such as a supercar, that’s when you need to take the effects of your car’s environment much more seriously.

This article lays down the case for why car humidity control should be at the top of your priority list, as well as the solutions that work (and the ones that don’t).

What is relative humidity?

Relative humidity is a means of measuring how much moisture is in the air relative to how close it is to saturation. The level at which the air becomes saturated will depend on the temperature, as warmer air can hold more moisture than cooler air.

100% RH means the air is saturated and can hold no more moisture. If the temperature drops, the air can no longer hold the same level of moisture, which means it will begin to deposit the moisture as condensation.

So what does this mean for car owners based in the UK? In the UK, the average RH sits at 80%, one of the highest averages across the globe. However, problems really begin to unfold when vapour is combined with our fluctuating climate.

We can owe this to our geography- the warm air we receive from the gulf stream and the cold air that arrives from subarctic weather systems, amalgamated with our island status (resulting in significant rainfall year-round), is a recipe for high quantities of moisture that is ready to condense on your car at the drop of a temperature.

What problems does it cause for your car?

High humidity and fluctuating temperatures are no friend to your car.

Problems caused by a high RH include:

• Iron corrosion and rust (50% RH and above)
• Steel corrosion and rust (70% RH and above)
• Mould growth in interiors (70% RH and above)
• Rubber degradation (65% RH and above)

This may lead you to think that the solution is to completely remove the presence of moisture from your car’s garage or storage space but that introduces other problems, such as dehydrated and cracked leather interiors (below 30% RH).

Ultimately, if you want to keep your car in the best possible condition, you’ll require a system that regulates humidity levels with accuracy and efficiency.

What are the commonly used solutions?

If you conduct a quick online search for ‘car humidity control’, you’ll be faced with plenty of budget products including the likes of dehumidifier bags, which are intended to sit inside your vehicle, as well as analogue humidity sensors.

Dehumidifier bags aren’t a bad option if your car sits outside year-round and you’re not too interested in protecting it long-term, as they do nothing to protect your car’s exterior. Not only that, but these bags will only have a marginal impact on your car interior’s humidity levels. This is because they are also usually single-use, meaning its effects is short-lived and less moisture is absorbed as time goes on. This makes it’s all-too-easy to forget that such products need replacing regularly.

Meanwhile, while analogue humidity sensors may serve the purpose of highlighting the fact that humidity is a very real threat to your car, they do nothing to actually deal with the problem.

If you take your car care seriously and already keep it stored in a garage, a dehumidifier will be the most effective option, as it allows better control over the environmental conditions that surround your car while it’s sitting inside. There are many different types of dehumidifiers on the market, but there’s only one obvious choice when it comes to car humidity control: the desiccant dehumidifier.

Why are desiccant dehumidifiers the best option for car humidity control?

The ideal conditions for most cars include maintaining an RH between 40-55%. This prevents corrosion, mould, cracked interiors, degraded rubber and the risk of electrical faults. To achieve this, you’ll need a system that can efficiently monitor and regulate the humidity of your environment, which is where a desiccant dehumidifying system comes in.

Desiccant dehumidifiers are made with synthetic absorbent materials which absorb moisture from their surrounding before recirculating the air to lower the RH. Unlike single-use dehumidification bags, this active system involves silica gel regeneration to keep the absorbent material working at all times and stop it from becoming saturated.

But how do they operate? With a Protect desiccant dehumidifier, you can program the system to keep the RH regulated within a window of your choosing. As the RH reading approaches the lower end of your ideal humidity window, the system will shut down automatically until starting back up when the RH climbs back to the higher end of the window, minimising energy output and running costs.

Desiccant dehumidifiers are also particularly well suited for colder temperatures such as the ones we experience in the UK compared to their counterparts, as they can operate effectively at temperatures as low as -20 degrees celsius without running the risk of overheating.