Psychrometrics – why understanding it is key to protecting your car




Car humidity control: Why it’s essential for protecting your car long-term

Psychrometrics is a little known term outside of science and engineering. However, having a grasp on what it is and how it works as a luxury car owner will allow you to understand how your car’s surroundings impact its health over time, making you better equipped to protect it. But what is psychrometrics? In simple terms, it’s the study of atmospheric air, including how temperature and vapour interact.

Protect car dehumidifier

Wherever your car is stored, the atmosphere surrounding it will also be interacting with the materials your car is made up of. If the concentration of moisture in the air is too high (or low), your car will be at risk of:

  • Corrosion and rust
  • Mould and mildew
  • Dry and cracked leather interiors
  • Rubber degradation
  • Electrical problems

This is due to relative humidity, which is simply the percentage of saturation at any given temperature. To prevent the issues mentioned above from occurring, you’ll need to maintain a relative humidity of 40-60%RH.

Psychrometric charts

The image below is a psychrometric chart, which shows the physical and thermal properties of moist air. The chart comes in handy for identifying humidity problems in your car’s garage or storage unit. This is because it provides a visual representation of the characteristics of how the air, temperature and moisture interact.

As you can see from the chart, there’s a lot of information. However, if you’re a car owner, you’ll only need to use a fraction of it to figure out the relative humidity (RH) of your environment. If you already have a dehumidifying system to keep your garage in check, you’ll be able to see how effectively it’s working.

If you are yet to invest in a dehumidifier, it should demonstrate the need for one- although these conditions will fluctuate, so if you’re working out the current RH of your garage for this purpose, make sure you complete several checks in different conditions.


How to work out relative humidity from a psychrometric chart

To work out the relative humidity of your environment, you’ll require a dry bulb thermometer and a wet bulb thermometer. Once you have the readings from the thermometers, you will be able to see the current RH.

On the chart, the figures for the dry bulb temperature run along the x-axis. The wet bulb saturation temperature is shown in the light blue figures along the curve. You will be able to see the resultant RH on the red curved line.

For example, if your dry bulb thermometer reads 25 degrees celsius and the wet bulb reads 15 degrees celsius, your relative humidity will be 50%RH, meaning your environment is safe for car storage at that time.

However, conditions fluctuate, and the result of one reading in an uncontrolled environment could be dramatically different when taken at different times.


What’s the best solution to keep your car protected?

A desiccant dehumidifier is by far the best choice of dehumidifier to keep your car’s garage in optimum conditions- but how does it work?

With a Protect system, you can select the RH window you want to maintain and the dehumidifier will consistently monitor your environment and regulate the humidity within that window year-round.

There other types of dehumidifiers available, but a desiccant system is efficient, cost-effective, low impact and quiet, making it a popular solution amongst car owners who are serious about preserving their vehicles.


While you could delve into researching the finer details of psychrometrics for hours, we hope this overview has provided a simple and easy way to work out your garage’s current RH and understand what steps you need to consider to keep your car in pristine condition. If you’re interested in finding out more about how desiccant dehumidification can help protect your car from the damaging impacts of humidity, get in touch.