Waterproofing and breathability explainedUpdated 43 minutes ago
Waterproofing and breathability explained
When you're choosing a performance jacket, waterproofing and breathability are the two biggest things to think about. One keeps the rain out, the other lets sweat escape, and getting the right balance between the two is what keeps you comfortable and dry on your ride, run or commute.
Waterproofing
What does a waterproof rating mean?
A waterproof rating tells you how much water pressure a fabric can handle before water starts to get through. It's measured in millimetres (mm), and the higher the number, the more waterproof the fabric is.
What do the numbers mean?
- 0 to 1,500mm: fine for light drizzle or a short trip out, but not built for heavy or long-lasting rain
- 1,500 to 5,000mm: handles moderate rain, good for everyday use in mild weather
- 5,000 to 10,000mm: proper protection against heavy rain and wet conditions
- 10,000 to 20,000mm: serious protection for intense weather, ideal if you're out in the rain a lot
- 20,000mm and above: top-level waterproofing for the wettest, most extreme conditions
Breathability
What is breathability?
Breathability is a fabric's ability to let moisture vapour (like sweat) escape, while still keeping water out. It helps regulate your body temperature, so you don't end up feeling clammy and damp from the inside when you're working hard.
What does a breathability rating mean?
Breathability is measured in grams per square metre over 24 hours (g/m²/24h), which tells you how much moisture vapour can pass through the fabric in a day. The higher the number, the more breathable the fabric is.
What do the numbers mean?
- Above 15,000g/m²/24h: excellent breathability, ideal for intense activities
- 10,000 to 15,000g/m²/24h: good breathability, suitable for moderate activities
- 5,000 to 10,000g/m²/24h: moderate breathability, better for less strenuous activities or cooler weather
- Below 5,000g/m²/24h: limited breathability, more suited to casual use
My jacket's breathable, so why do I still feel wet inside?
This is one of the most common things people get caught out by. A breathable jacket helps sweat escape, but it can't stop you sweating, and there are a few reasons you might still feel damp inside:
- Sweat: if you're working hard, your body can produce sweat faster than any fabric can let it out
- Condensation: in cold or very wet weather, moisture from your body can turn into condensation on the inside of the jacket, which can feel like it's leaking when it isn't
- Fit: if a jacket's too tight, there's less room for air to move, which makes it harder for moisture to escape
- Fabric saturation: during long spells of heavy rain or hard exercise, the outside of the fabric can become saturated, which reduces how well it breathes
All of this is completely normal and happens with every waterproof jacket, however breathable it is.
Layering properly
What you wear underneath your jacket makes a big difference to how dry and comfortable you feel:
- Base layer: wear a moisture-wicking base layer, such as a technical sports top or merino, next to your skin. Avoid cotton, as it soaks up sweat and holds onto it, leaving you damp and cold
- Mid layer: on colder days, add a light fleece or insulating layer for warmth, and take it off if you start to get too hot
- Outer layer: your waterproof jacket goes on top to keep the wind and rain out
- Adjust as you go: open zips or vents, or take a layer off, if you start to warm up. It's much easier to stay dry by not overheating in the first place
Getting the balance right
The best jacket for you depends on how and where you'll be using it:
- Activity level: the harder you're working, the more breathability matters, so you don't overheat
- Weather: if you're regularly out in heavy rain, look for a higher waterproof rating
- Seams: even with a high waterproof rating, water can sneak in through the seams, so look for taped or sealed seams for the best protection
- Fit: choose a fit that gives you room for your layers underneath
Looking after your jacket
Over time, the waterproof coating on any jacket will naturally wear down, which can also make the fabric saturate more quickly. Take a look at our re-waterproofing article to find out how to keep your jacket performing at its best.