Mark Rhodes Protect by Dehum


5 Types of Dehumidifiers: The Most Effective Garage Dehumidifier for Your Car

When it comes to researching the best garage dehumidifier to help protect your car, it can be a challenge to even know where to start. Not only is there an array of dehumidifiers on offer that come in all shapes and sizes, but aspects like cost of running, efficiency and the method of dehumidification will vary from unit to unit, so there’s a lot to consider before you commit to investing in a dehumidifier that you will be running for years to come.

Why does your car need a garage dehumidifier?

It’s a common misconception that storing a car in a garage or bubble equates to protecting it from coming into contact with water.

However, just because your car’s garage is ‘weather-proof’ does not mean that your car is fully protected from other environmental factors- even if you choose to store it in a product such as a car bubble, which only works to keep your car clean. Ultimately, whatever the weather looks like outside, there’s one thing you can count on being there: humidity.

This is a problem, particularly for UK-based car owners who have to deal with the adverse impacts of high relative humidity year-round. As a result of poor storage, we believe that many car owners end up paying much more for costly repairs, refurbs and replacements than it would cost to purchase and run a garage dehumidifier.

Dehumidification as a solution to protect your car

Using a garage dehumidifier is really the only effective way to entirely remove the risk of corrosion, rusting, leather interiors cracking and mould growth in your garage environment.

Some of the most common types of dehumidifiers include:

  1. Desiccant
  2. Car dehumidifier bags
  3. Refrigerant
  4. Whole house
  5. Heat pump dehumidifier


Each of these serves the same purpose of removing moisture from your environment, but some are better suited to your car garage than others. In this article, we’ll take a closer look at how each works and which would be best suited for your garage dehumidifier. But first thing’s first: what exactly is relative humidity and what kind of damage can it cause your car?

What is Relative Humidity?

Relative Humidity (RH) is simply a measurement of how much water vapour is present in the air relative to how much water-holding capacity the air has at that temperature. The higher the temperature, the larger capacity the air has to hold water vapour.

In the UK, the average RH sits at 80%, one of the highest global averages. The result? High levels of humidity combined with fluctuating temperatures can spell disaster for an unprotected car. For example, rust can occur when the RH climbs above 50%, while mould is able to grow and steel can rust when the RH reaches above 70%.

But this is where it can get tricky: too low a humidity can also damage your car. Expensive leather interiors are at particular risk if the air is too dry- leather begins to dry out, leading to cracking, if the RH sits below 30%. As a result, it’s important to not only reduce the humidity in your car’s garage but control it within a preset window that will ensure your car is protected from the adverse environmental damage around the clock.

1. Desiccant dehumidifiers

Desiccant dehumidifiers work using synthetic adsorbents including silica gel, activated alumina and molecular sieves. As the dehumidifier draws air in, the adsorbent actually produces a physical change-of-state, where the hydrogen and oxygen atoms that make up the water molecules dislocate, removing water vapour from your surroundings.

So that’s how it works, but how will it fare as your garage dehumidifier? Desiccant units make up all of the best options for car storage.

Some of the key benefits include:

  • They’re quiet and low impact- they don’t include clunky compressors or coils.
  • They don’t cost the earth- they’re efficient and cost-effective to run.
  • Reduced risk of overheating- as drying can be achieved at -20 degrees celsius.
  • It stays effective around the clock- silica gel regeneration stops it from becoming saturated.
  • They can work on any scale

Over the past 3 decades in the UK, the average coldest day was -4.5 degrees Celsius, but temperatures do fluctuate. The Met Office predicts that we will begin to see warmer and wetter winters in the UK from the effects of climate change, meaning more moisture in the air, and more chance of it condensing on and damaging your car.

So as well as making a great all-round choice for most car owners passionate about protecting their car around the work, desiccant dehumidifiers are particularly suited to UK drivers, as they work effectively in cooler conditions and can deal with an array of fluctuating conditions better than the other options.

2. Car dehumidifier bags

Car dehumidifier bags aren’t exactly a powered dehumidifying system like the rest in this article, but they do deserve their own mention as they use some of the same techniques as a desiccant dehumidifier and use a method known as passive dehumidification.

Much like the desiccant dehumidifier, car dehumidifier bags rely on desiccants- where a hygroscopic substance, like silica, is used to change the state of it’s sealed container by drawing moisture from its surroundings. They’re essentially a larger version of the small gel packets you’ll find in sealed containers, such as shoe boxes.

However, the benefits are pretty limited to price alone- car dehumidifier bags are not a big investment, but they fall short of what their electrically powered counterparts can achieve for your environment.

Some of the biggest issues include:

  • They’re single-use- while a desiccant dehumidifier will dry its hygroscopic substance so it can continue to operate just as effectively. Dehumidifier bags just become saturated and ineffective.
  • They’ll only impact your humidity inside the car- making them an acceptable option if your car sits outside throughout the year, but only the interior will receive the benefits of dehumidification- leaving the rest of your car at risk of corrosion and rust.
  • The overall cost/benefit ratio for passive dehumidification is extremely poor.

Overall, dehumidifier bags do not make the best choice of garage dehumidifier. There are far more options that work as a full solution, not just a supplement to a solution, like the gel bags.

3. Refrigerant dehumidifiers

Refrigerant dehumidifiers are usually recognised as the most commonly used dehumidification model. To remove surrounding moisture from the environment, a refrigerant dehumidifier creates a cold surface using coils, over which air is passed, when the air hits that surface the moisture contained within it condenses before being collected and removed.

The reason these units are so popular is that they’re known to be efficient and can be inexpensive to run- but this low cost depends on where you are and its intended environment.

While they may be a contender for climates that are hot year-round, they don’t make the best garage dehumidifier for your car because they work best in warm conditions. If you invest in a refrigerant dehumidifier for your UK garage, you could find yourself with the additional cost of having to run a heater alongside it throughout most of the year in order to get the vapour to condense on the cold surface of the unit. This can result in big yearly energy bills, especially if you have a larger garage that requires more than one heater- however, that cost can easily be avoided with a unit like the desiccant dehumidifier.

Refrigerant dehumidifiers summary:

  • Noisy- get one of these and it could be worth investing in some noise-cancelling earplugs!
  • Functions best in warm conditions- making it appropriate for summer temperatures
  • Does not alter surrounding temperature- you may find yourself with an additional heating bill
  • Better suited to in-home environments
  • More appropriate as a temporary humidity solution


Overall, these models are generally better suited to an in-home environment- but be aware of the level of noise they generate- they can be significantly more loud and clunky than the desiccant dehumidifier options.

4. Heat pump dehumidifiers

Heat pump dehumidifiers are a type of refrigerant dehumidifier, as they use an electrically driven refrigeration cycle. The cold evaporator coils in the unit condenses the surrounding water vapour, while the warm condenser heats the cooled dehumidified air before it’s reintroduced into the environment.

However, these units can become very expensive to run and aren’t as efficient as many believe, especially when it comes to aspects such as ‘sensible cooling’, which is the process of removing heat from the air.

As a result, when compared to a desiccant option as a garage dehumidifier for your car, heat pumps have a big question mark over sustainability. Not only that, but cold weather can actually damage the system, and so housing it in your garage is probably not the best application.

5. Whole house dehumidifiers

Last but not least, a whole-house dehumidifier is more or less what it sounds like- it’s a dehumidifier that’s fitted into your home with the goal of managing the humidity levels across the property. This makes it a great solution if your humidity issues extend outside your car’s garage. However, the application is in the name: these models are better suited for in-home applications. They are more efficient than a single-room dehumidifier- but regulating the humidity of a whole house, including the garage, is probably going to land you with a large energy bill, as well as being expensive to install and move.

Which is the best garage dehumidifier for your car?

Out of the 5 dehumidifiers discussed, there is one clear winner for your garage dehumidifier: the desiccant dehumidifier. Already perfectly suited to efficiently and cost-effectively managing UK conditions, investing in your own will see you save on the costs of repairs, refurbs and general upkeep over your car’s lifetime. Our team can provide you with a sleek, low impact bespoke model that’s specific to your individual needs and is perfect for protecting your car- so what are you waiting for? Click here to get in touch to find out how we can help to protect your car today.

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