How Can a Jacket Be Waterproof AND Breathable?
Because many waterproof jackets tend to get drenched with sweat on the inside, there’s a belief that a waterproof material can’t also be breathable.
But how true really is this? Is it possible for a jacket to be waterproof and breathable?
We’ll take a look at this below, as well as what breathability and waterproof IP ratings mean, what ‘waterproof breathable’ means and how this fabric works.
Why Does My Rain Jacket Get Wet Inside?
There are two main causes of this. This first is perspiration – i.e. sweating. This produces water vapour and will condense on your jacket’s interior.
The second is condensation – when water changes from its gaseous form (water vapour) into a liquid after hitting a colder surface. Humid air contains a great deal of water vapour, so if the outside of your rain jacket is colder than the inside, condensation will occur, dampening it.
What Does ‘Waterproof Breathable’ Mean?
As it happens, not every waterproof jacket is lacking in breathability.
Perspiration droplets are smaller than that of normal water, so if a material’s stitching has holes too small for rain but larger than sweat drops, it should be pretty breathable.
That’s where ‘waterproof breathable’ jackets come in.
How Does Waterproof Breathable Fabric Work?
Specifically built for releasing the water vapour building up inside your coat, they have a breathable layer with tiny pores, which can simultaneously vent out the water vapour and act as a barricade to rain drops.
A jacket with waterproof breathable fabric will normally find this layer sandwiched between its other materials due to how thin and fragile it can be.
These must remain clean, though – if not, it could affect the passage of water vapour through the waterproof breathable fabric. To do this, wash frequently and coat the jacket’s exterior with durable water repellent (DWR).
With DWR added to the jacket, rain will run off it far more efficiently, allowing the waterproof breathable to prevent water from sinking in to it more effectively. Though, it’s worth bearing in mind that the DWR coating will disintegrate over time through basic wear and tear.
What Material is Waterproof and Breathable?
There are two parts to this. Firstly, Waterproof breathable materials are often made of an outer layer – known as the ‘face fabric’ – often made of nylon or polyester.
But they also boast a laminated membrane or coating, which is typically made of ePTFE (expanded Polytetrafluoroethylene, also known as Teflon) – the like of which you find in Gore-Tex products – or PU (Polyurethane).
What is the Most Breathable Waterproof Jacket?
We love the Rapha Lightweight Commuter Jacket – not only for its waterproof breathable functions, but also for how portable it is and how much it offers in terms of visibility.
But while you’re here, be sure to check out out top three lightweight packable waterproof breathable cycling jackets for both men and women too (click here for our favourite waterproof cycling overtrousers).
Waterproof IP Ratings: Explained
An IP (Ingress Protection) rating determines the level of protection offered against foreign bodies – so in the case of waterproof jackets, how well they guard against water.
As a general rule, waterproof IP ratings range between IP65, IP66 and IP67, yet it’s not always the case that items used outdoors frequently require the highest numerical IP rating available.
The first digit refers to the level of protection against solid objects and dust, while second concerns how well it guards against ingress of liquid.
- If the first digit is six, it totally protects against dust and protects against access with a wire.
- If the second digit is five – ‘Protection from water jets. No harmful effect of water splash from all directions’.
- If the second digit is six – ‘Protection from strong water jets. No harmful effect of strong water jets from all directions’.
- If the second digit is seven – ‘Protection from water dip. No harmful effect of water dip in certain level of pressure and length of time’.
What IP Rating is Fully Waterproof?
An object with an rating of IP68 is fully dustproof and fully waterproof.
This means that you can submerge it in water of up to 3m in depth for more than 30 minutes.
Breathability Ratings: Explained
There are more variables to a jacket’s breathability – temperature, humidity number of layers you’re wearing; these will all affect how much we sweat and how quickly we transfer water vapour (i.e. how breathable it is).
The most common and probably best way to measure breathability, then, is by a Moisture Vapour Transmission Rate, which concerns the amount of water vapour that can pass through a square metre of material over the course of 24 hours. Using this method:
- < 5,000 g/m² = not very breathable
- Between 8,000 g/m² and 20,000 g/m² = good level of breathability for general outdoor use (e.g. walking)
- > 20,000 g/m² = best level of breathability for highly aerobic use
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