Breathable Car Covers
Why is using a breathable car cover so important? For Car Covers to function properly and as intended, they must be able to breathe. Of course by "breathe" we mean to allow water vapor or moisture in gas form to pass through the cover itself. We consider this one of the most important properties to look for in a Car Cover, especially an outdoor car cover.
Breathable Car Covers vs Waterproof Car Covers
Breathable car covers allow trapped moisture and condensation to evaporate quickly, thus shortening the amount of time your vehicle is exposed to wet, humid conditions.
Why not just use 100% waterproof cover to keep the water off?
When you have a 100% waterproof cover, you sacrifice breathability. For a completely waterproof cover, the seams are sealed closed with an ultrasonic machine instead of sewn (sewn seams have small holes from the needle, which can cause some water to seep through), allowing the material itself to prohibit water passing through, regardless of the precipitation's velocity.
While a 100% waterproof cover protects from external moisture, it unfortunately is more prone to moisture condensation beneath the cover. Under humid conditions, water droplets will form (like dew) underneath the cover itself. Once there, the water droplets remain trapped for extended periods of time because of the moisture's inability to evaporate through the cover, thus compromising the vehicle's paint job. However, the breathable car cover's allowance for quick evaporation enables the cover to continue protecting your car's finish with little compromise to moisture.
Another factor to consider with moist conditions, is the increased likelihood of rust and corrosion, as well as mold and mildew. It only takes a small pit or scratch in the car's paint to allow the start of rust and corrosion. With a breathable car cover, if water gets through or forms due to condensation, you have nothing to worry about as the water will evaporate before any corrosion can begin.
The covers breathability and water repellency are usually inversely related. What this means is that... the higher the water repellency is, the lower the breathability will be, and vice versa. With some of the high-performance materials that are available now, there is less of an inverse correlation - but the principle still remains true. Keep this in mind when selecting your outdoor car cover material.
Car Cover Materials Comparison chart for more details.