Are Down and Insulated Jackets Waterproof?
While we’ve said synthetically insulated jackets are better at handling moisture, these coats, like down filling, are not waterproof. They are much more likely to be water-resistant, meaning that they can stand up to showers. In heavy rain, down jackets will lose their loft, becoming wet and heavy and taking a long time to dry out.
This is why you may have heard of hydrophobic down, where the down is treated with a water repellent coating. This doesn’t mean the jacket will still work when soaked but it will dry quicker, won’t absorb as much water. It will also retain its warmth much better than regular down.
The reason why these jackets aren’t waterproof is that down insulation needs to be able to breathe. A waterproof membrane would make you very hot, making you open the jacket to vent. Then, you’d cool down quickly and end up repeating this all day. Plus, down is designed mainly for snowy conditions rather than heavy showers.