Waterproof breathable rain jackets are not permanently breathable. Instead, they’re coated with a chemical formulation called DWR, which stands for Durable Water Repellancy, that causes water to bead up on the jacket surface when it rains and roll off.
The problem is that this DWR coating rubs off after a time, so your jacket soaks up the rain rather than repelling it. This moisture clogs the passages that water vapor is designed to pass through causing it to condense back to liquid form inside your jacket and making your underclothes wet.
When the factory-applied DWR coating that a rain jacket comes with wears out, many people simply buy a new rain jacket. Others try to reproof the DWR coating using aftermarket restorative formulas like:
These products can be sprayed onto the outer surface of the jacket to restore the DWR coating or washed-in in a washing machine which is more effective and longer-lasting.
Unfortunately, these aftermarket treatments do not last as long as a jacket’s original factory DWR coating, but they will restore its ability to repel raindrops and vent the water vapor your body generates when it perspires. On average they last about 1/2 the time as the factory DWR coating, but this depends greatly on the frequency in which you use your jacket and how much abrasion the outside of your coat experiences.SectionHiker is reader-supported. We independently research, test, and rate the best products. We only make money if you purchase a product through our affiliate links. Help us continue to test and write unsponsored and independent gear reviews, beginner FAQs, and free hiking guides.