The ultimate guide to waterproof ratings and breathability
Welcome to the ultimate guide to waterproofing and breathability. If there’s anything you ever wanted to know about this subject, you can find it right here.
If you’ve ever wondered what’s the big deal about waterproof ratings and breathability when it comes to outdoor and ski gear, then you’re not alone. What at first may seem like a black and white subject, can be all at once overwhelming when you dive beneath the surface. But that’s why we wrote this guide, and why you’re here. This is the ultimate guide to waterproofing and breathability. Everything you need to know to make informed decisions about your ski jackets and ski pants. And lots of super interesting facts, too.
Quick find navigation
Mastering the science of ski gear
As snow enthusiasts, being informed about waterproof and breathability ratings of your gear is essential. This guide serves as your resource to smartly navigate the myriad options in outdoor clothing, specifically when choosing items like ski jackets and ski pants Equipped with this knowledge, you'll be ready to hit the slopes in every condition. Plus, we have sprinkled in some fascinating facts to enrich your understanding. Enjoy the adventure and stay warm out there!
What is waterproofing and how is it measured?
Waterproofing is the sliding scale of how much water a fabric can endure before it lets any moisture through. Wait… what? Surely a fabric is either waterproof or it isn’t? Uh, you’d think so, but no. Anything about 3,000mm is rated as ‘waterproof’. But why is it measured in ‘mm’? This is a rabbit hole situation, so let’s backpedal and take it from the top.
Waterproofing is measured in ‘mm’ because of the hydrostatic head test. We’ll explain what that is below, but before we get onto that, let’s get down to brass tacks, and explain what the numbers mean in real-world terms, because they’re likely what you’ve come across on your shopping travels.
Waterproof ratings: what do the numbers mean?
While ‘waterproofing’ begins at 3,000mm, anything up to 5,000mm is only going to stand up to a light shower, maybe some drizzle. Some outdoor jackets with this rating might be things like super lightweight and packable jackets. Snow jackets that have this rating are likely meant for the park or fairweather riding, not for snowstorms or ploughing through powder!
Between 5,000mm and 10,000mm things are getting a little more stable. A lot of generic brand items will be in this range. They’re okay for resort skiing or boarding in good weather, but won’t stand up to much punishment and won’t be much use in the rain.
10,000mm or 10k is often the industry standard for branded snow goods. Very rarely will you see a branded piece of snow gear with less than 10,000mm of waterproofing if it’s designed for general use. This range has good resistance to the elements without breaking the bank, and is usually where the entry-level or standard gear from most brands slots in.
15,000mm is quickly becoming the benchmark for many brands, and thanks to better technology, it’s more attainable than ever at an affordable price. 15,000mm is reliable and solid for use all over the mountain, in all weathers. 15,000mm is more waterproofing than most riders will ever need.
As we get above 20,000mm, you’re looking at serious performance. Most brands’ ‘performance’ or technical ranges tend to be in this category. Mass produced (ie. generic, rather than patented brand specific) technical membranes usually top out at this kind of figure, but it’s more than enough for riding in even the worst weathers!
25,000mm is when you start to get into that more ‘black and white’ level of waterproofing, ie. if it’s above 25k, then it’s never going to let water in. Gore-Tex offers a dryness guarantee, and it’s rated at 28,000mm, for reference! Anything sporting a 25,000mm water column or more is a serious piece of gear ready for the toughest adventures. Blizzards, hurricanes, you name it, let’s go!
Gore-Tex is the brand that single handedly took waterproofing from non-breathable plastic sheets to breathable membranes. Heated and rapidly stretched PTFE creates a microporous synthetic fabric that keeps water out, but lets vapourised sweat through, for industry leading performance, decades on from its original conception. Their range now contains many different iterations, but all possess the same great performance.
FUTURELIGHT is The North Face’s answer to Gore-Tex, and is a lightweight membrane that they pair with their DryVent fabrics in order to provide an extra layer of performance on their top of the line backcountry gear.
Other brands also have their own versions of high-performance waterproof membranes. Patagonia have their H2No fabric, while the brands Pertex Shield and Sympatex also produce technical membranes that are widely used. eVent might also not be a household name in the sportswear industry, but their fabrics have been used for years by lots of top brands, too.
How is waterproofing tested?
When it comes to representing waterproofing, we use a measurement in millimeters. But what does length have to do with waterproofing? Well, it’s a bit of a strange method, but it’s one that’s now used as an industry standard, and it’s called...
The rating you see on fabrics and gear (25,000mm, for example) is actually what’s known as the hydrostatic head of that fabric. In laymans, that’s waterproofing, but the science behind it is interesting. Waterproofing isn’t measured over time — ie. how long will this fabric endure rain? But rather by using water pressure in the form of weight. Eh? What does that mean? Well, let’s look at how the test is administered.
A piece of the fabric being tested is spread flat, and a one-inch diameter tube is placed on top of it (standing upright). Now, water is poured into the tube, and as more water is added, the weight increases, and so does the water pressure pressing down on the fabric. This tube is of an indeterminate length, but has measurements on the side. 1,000mm (which is one metre), 5,000mm, 10,000mm… you get the picture.
More and more water is poured in, and as it begins to rise up past these measurements, if the fabric continues to hold the water back, then it achieves that ‘rating’. Once water begins to seep through the fabric, the test is over, and whatever milestone it reached, that’s it’s rating.
Of course, this test is repeated multiple times on the same fabric piece and different fabrics, and they average the scores, and then usually choose a round rating below those averaged scores. Otherwise you might get a jacket with a label saying 17,382mm waterproofing, and then you’d be even more confused.
Why is waterproofing important in outdoor clothing?
This may seem like a strange question — er, to keep you dry, right? But when we’re talking about ‘modern’ waterproofing, we’re talking waterproofing and breathability, and we’re talking about the science of why staying dry is vital. This can be condensed into one simple chain of reasoning — water conducts heat away from the body around fifty times faster than air. If you’re wet, you get cold. If you get cold, well, it sucks. So dryness equals warmth. Or at least the ability to retain warmth more efficiently.
And that’s why waterproofing is prioritised for backcountry and adventure clothing, because the further you are away from civilisation, the more dangerous it is to get cold and wet. And as you might guess, if you get wet, it’s probably because of rain or snow, and if you got wet, then it’s probably going to be impossible to dry off. So, staying dry is better than trying to dry off. You know, to avoid hypothermia, and, uh, death, we guess…
Waterproof fabric construction: laminated layers
Waterproof fabrics, however, don’t achieve ‘performance’ with just a waterproof membrane. The membrane is the powerhouse of the fabric, sure, but they can actually be quite fragile. Membranes need to stay protected to work correctly — and things like abrasion and friction, oils, dirts, contaminants, they can all adversely affect the way that a membrane functions. A membrane works because it’s microporous. A micro-pore might be several hundred times smaller than a liquid water droplet, so it can get clogged really easily. That’s why waterproof fabrics sandwich the vulnerable membrane between inner and outer layers through what’s called lamination.
Lamination is the process of pressing these fabrics together under heat to bond them at a molecular level. The outer fabric, or ‘shell’ fabric acts as a barrier to external contaminants and abrasion, while the inner fabric or ‘liner’ protects the membrane from the oils, sweat, and friction produced by your body.
How a shell fabric works
A shell, much like on a snail, is a protective layer. Shell fabrics on outdoor clothing are abrasion resistant, malleable, and are synthetic. Synthetic fibres are derived from plastics which are extruded into ‘threads’ and then woven together. These fabrics offer great durability and longevity, and importantly, the ability to hold a DWR coating.
Synthetic materials can be bonded to a membrane, too, which is vital when creating a waterproof fabric. They are also much more resistant to absorbing moisture or oils, and can be wiped clean easily when compared to something like cotton or wool! Their versatility makes them ideal for use in high performance outdoor clothing like ski and snowboard wear.
What is DWR and how does it work?
DWR stands for Durable Water Repellent, and is a chemical treatment that is applied to the outer shell of a fabric. At a molecular level, DWRs are slippery. They have a low friction coefficient, which means water can’t ‘cling’ to them. Put this substance on the fabric of a jacket, and you make it so water doesn’t soak into the fabric, it just rolls off. The surface tension on water, or the meniscus, causes it to bead or pearl up on the surface (like a droplet of water on a non-stick pan, which is pretty much the same material as a DWR), and then roll off.
While this doesn’t increase the waterproof rating of the membrane or fabric, what it does is stops as much water from reaching it. In essence, it repels moisture, giving your membrane a chance to work for longer. The jacket isn’t therefore ‘more waterproof’, but will keep you dryer for longer versus a jacket with no DWR coating.
Shell fabrics
Polyester is one of the most common and versatile synthetic fabrics in the world. Used to produce a wide array of materials like chiffon, velvet, and even some denims, polyester is everywhere; including outdoor gear. Polyester is an extremely durable material, is naturally moisture resistant due to its low friction coefficient which makes it wicking (draws moisture away rather than absorbing it). It’s also resistant to stretching, can be woven in a variety of ways, and in different textures, too, making it possible to craft rough, smooth, or textures fabrics for different reasons and desirable. Fleece, for example, is rough polyester and is a great insulator. A ski coat on the other hand, is likely to have a smooth outer to prevent it from getting dirty or snagging on things.
Nylon is quite like polyester, and is becoming more popular to use in outdoor clothing due to its extremely durable characteristics. Nylon is also stretchy, where polyester isn’t, so it’s very useful when creating ‘functional’ fabrics that need to move, flex, or have a degree of elasticity. Nylon can be worked in a variety of ways, too, but results in a smooth, soft texture when woven. This makes it perfect for outer shells where durability is key, but not so great for fleeces or base layers, where polyester is still very popular due to its versatility in regards to feel and comfort.
Some companies are beginning to use polyamide fabrics. These are actually just nylon, in essence, with nylon being the generic name for a family of aliphatic or semi-aromatic polyamide polymers. As such, all nylons are polyamide, but not all polyamide is nylon. Does that make sense? Polyamide, therefore, is the overarching term used for any polyamide fabric. These can have specific characteristics tailored to the use, but generally possess the same level of durability and functionality as nylon.
How a waterproof membrane works
As we covered above briefly, a waterproof membrane works by way of micropores. A synthetic material is heated and then stretched quickly, creating a thin membrane. This membrane looks solid to the eye, but contains millions of microscopic holes. Water molecules that occur in nature, ie. rain and snow, will be too large to pass through this membrane. However, when we sweat, our body lets out vaporised water molecules, which are much, much smaller. Small enough, in fact, to pass through the micropores. Which is why water is kept out, and sweat is let out. When this happens, it’s called ‘breathability’, but we’ll discuss that in more detail below!
Membrane materials
Material science has come a long way in the last five decades, and now, technology has moved on from the standard PTFE membranes to more environmentally sound alternatives.
The original super material, polytetrafluoroethylene is a long-chain polymer created accidentally by the DuPont corporation. It’s water-repelling properties were quickly identified and put to work as coatings for non-stick pans. Unfortunately, it became quickly apparent that the process of creating PTFE released a lot of harmful chemicals which ended up being terrible for the environment, and the people who worked there. It’s a whole big legal and environmental thing (which is still ongoing and can be looked up) but the things made possible PTFE have raised the bar massively for waterproof clothing.
Processes have come on, and are now much less harmful, and some companies still use PTFE for their membranes and DWR treatments. Gore-Tex was the company to champion PTFE and put it to use in activewear, but now they are making a push towards environmentally sound alternatives. Though you can still find this substance fairly commonly used. Don’t worry, in its processed form, it’s completely harmless.
Thermoplastic polyurethane and polyurethane (respectively), are basically the same material, except TPU is a ‘thermoplastic’, meaning that it can be heated and made soft and malleable again, whereas PU is thermoset, which means that once it’s been processed and cooled, it cannot be reshaped under heat. What does this mean, then, for waterproof membranes? Not much in regards to the differences. PU and TPU don’t have a big environmental footprint, and don’t produce harmful by-products in the same way PTFE does, but they do possess the same performance and waterproofing and breathability characteristics as PTFE, which is why TPU and PU membranes are taking precedence over their more polluting forebearer. For you, the consumer, the difference in performance is nil, but you may still wish to know what you’re wearing on your back!
How a liner works
A liner fabric is designed to put a barrier between you and the waterproof membrane. We spoke earlier about how oils and dirts can contaminate a membrane, and a liner is the main line of defence against that happening. The soft material will be comfy against the skin, but forms a barrier to stop the membrane getting damaged by friction or dirt.
Liner fabrics
Polyester is used as a liner fabric because it doesn’t absorb moisture, is wicking (draws moisture through it), and can be made soft and smooth, or rough and fleecy. This means that a jacket can be fully lined with polyester, and it won’t get wet with sweat, and can be super cosy and comfortable, too. It also won’t absorb sweat over time, so will stay fresher for longer versus something like wool or cotton. Polyester is used pretty much by every outwear and activewear company due to these great properties!
What is breathability, and how is it measured?
Breathability, simply, is the amount of water vapour that can be let out through a fabric. Water vapour is what your body produces when you sweat. We release it continually — and when we’re working really hard, it turns into sweat because our body exudes so much of it that it globs together. Our body does this on purpose as a form of heat management.
As such, a jacket with a high breathability rating won’t stop you from sweating — but what it will do is make it so that the water vapor your skin releases can pass through the fabric and be released. This helps to keep you dry, and prevents clamminess and dampness all over. Which is what happens when this vapour gets trapped. High breathability is key for staying dry during long days on the mountain.
Breathability ratings: what do the numbers mean?
The higher the number, the more breathable a fabric is. Breathability is often measured in a ‘g/m2/24hrs’ measurement. This is the amount of moisture by weight that can pass through a square metre of fabric over the course of 24 hours.
Jackets in this range are likely going to be fairly ‘casual’. Off-brand or generic brand ski and snowboard wear, or low-end wet-weather gear will be sub 10k, and offer little in the way of functional breathability.
Getting more useful, between 10k and 20k is going to be pretty usable. More often than not, fabrics will have matching waterproofing and breathability ratings. 10-20k is standard for the industry and will do a decent job of getting rid of excess heat and moisture.
Getting into the performance range, 20k-30k of breathability will stop you from getting damp and clammy unless you’re really pushing the pace and working up a sweat.
30k and above is pretty much as breathable as things get without sacrificing waterproofing. You likely won’t notice too much difference from a 20k-30k rating at this stage, so don’t go out of your way to look for something up here, because as we said above, if you’re sweating, you’re sweating, and no amount of breathability will prevent that.
How is breathability tested?
There are several breathability tests that produce different types of ratings, so let’s look at what they are below.
This rating is the standard used by most companies, and is the g/m2/24hr figure we’re used to seeing. This rating represents the amount of water (or sweat) by weight that can pass through a square metre of a fabric over the course of a day. A higher rating means better breathability.
Method one is called the Upright Cup Test. Calcium chloride is placed into a cup, and a piece of fabric is then secured over the top. After a period of time, the cup is weighed to see how much water has been pulled into the cup from the air. This weight is then used to calculate the breathability of the fabric. The higher the number, the more vapour can pass through, and the more breathable it is. This test produces a grams per twenty-four-hour, or g/m2/24hr figure.
A second method is known as the Inverted Cup Test. Potassium acetate is placed into a cup and sealed with a piece of ePTFE film. The tested fabric is then placed over the cup, and the whole thing is turned upside down and placed into a container of water. The cup is then left for a period of time, before being removed and weighed to see how much water has been pulled into the cup itself. Depending on the length of time and the weight, a figure is then extrapolated to produce a grams per twenty-four-hour, or g/m2/24hr figure.
The RET rating is often used by GoreTex to represent the breathability of their garments. This rating is the inverse of the MVT in that a lower rating means better breathability. Ratings will often be shown as a less or more than figure, ie. RET <9, which means that the fabric has a RET rating of less than 9. Which is quite good, for the record. This figure is produced by way of the sweating hot plate test, and is derived from the measurement of the amount of energy required to keep the plate at a specific temperature while water evaporates from it, through a fabric.
A piece of fabric is placed over a porous or sintered metal hot plate. Water is then channelled into the plate and evaporates from the surface to simulate perspiration. As water evaporates through the fabric, it causes Evaporative Heat Loss. Higher heat loss means more evaporation and higher breathability. This produces the RET figure, which is the measurement of the resistance to heat loss in the plate (not the fabric). The lower the RET the more evaporation there is, with more vapour moving through the fabric, which means higher the breathability of the fabric.
Why breathability is important in outdoor clothing?
Outdoor clothing generally means clothing that you would wear when outdoors for activities like hiking, mountain biking, skiing, snowboarding, or anything else of that nature. Much like when a car gets going, the engine generates heat. The higher the engine revs, the more heat it puts out, the more fuel it uses. Your body is the same thing — you process food, turn it into energy, and that energy is used to power your muscles. Now, if you paid attention in school, you’d know energy doesn’t get used up, it gets converted.
All that heat has to go somewhere, and while lots of it is exhaled in your hot breath, your skin puts out a lot of it, too. Breathable clothing allows that heat to escape. The problem isn’t the heat, though, but the moisture. On its own, it’s not a problem. But as it begins to build up, it cools, condenses, and then clumps together into moisture. This then makes you damp, and we already know water conducts heat away faster than air! Which means you get cold. So, weirdly, you need clothing that’s breathable and can let heat out in order to stay warmer.
Synthetic materials are best when it comes to breathability because they don’t absorb moisture. Polyesters and nylons can be highly breathable because their synthetic makeup doesn’t allow the fibres to hold onto moisture efficiently. A dry material will breathe much more efficiently than a wet material, so materials which resist moisture perform better for longer.
The term ‘wicking’ also gets thrown around, but all a wicking material is is one that’s moisture resistant — so moisture passes through, rather than sticking to it, which allows for consistent breathability. This is why materials like cotton or wool can be breathable to begin with, but their efficiency drops once they begin to get moist. As such, synthetics are the way to go when you’re talking about breathability!
Other breathability factors
When it comes to breathability, it’s not just the rating that helps you let off steam. Jackets and pants are designed with other elements to help reduce moisture and sweat build up to keep you riding at your best.
Linings are designed to help wick moisture away and be highly breathable, lightweight, smooth polyester fabrics can work to pull sweat from the skin and push it towards the outer shell so it can be efficiently released. This extra layer helps you stay drier for longer.
Zips, vents, and mesh panels are another addition to winter clothing especially. Zippers in the armpits, at the collar, and in the groin/thigh area allow circulation of air. And because of how diffusion works, a more dense gas will move into a less dense gas, so that water vapour coming out of your skin will naturally push towards colder air. This is why getting a jacket or pants with vents is essential for those looking to work up a sweat!
How waterproofing and breathability work together
While they may seem like opposites, waterproofing and breathability work in tandem to create a functional jacket. Waterproofing is essential to keep the snow from soaking through to your under layers and body when you’re skiing or boarding, while breathability is the thing that keeps you dry inside. Unfortunately, our bodies never got the memo that humans wear clothes, and our biology is still firmly rooted in the stone-age. So when we head up the mountain all layered up, naturally our bodies will try to keep us cool and thermo-regulate for optimum performance. Which is most of the problem!
It’s only natural to be cold before you start and then hot when you get going, which means those layers will work against you. On the mountain, the sun may feel warm, but the air is actually really cold. And when you consider that your body temperature only needs to drop a couple of degrees for you to be in serious trouble, staying warm is always priority one.
Now we’ve already gone over this, but just to quickly recap — moisture is the enemy of heat. Your skin is really good at holding on to heat when it’s dry, but pretty bad at doing it when it’s wet. Water will suck heat from your body, and if your base layers, mid layers, and jacket are wet then that heat is just going to radiate off you.
It’s nearly impossible to get dry on the mountain, so staying dry is a necessity. There’s no point having breathability if your jacket lets water in at the first sign of slush. And there’s no point having a waterproof shell if all your sweat is going to make you wet anyway! So realistically, it’s a symbiotic relationship. Neither can work without the other, which is why they’re both just as important as each other.
FAQs about waterproof and breathability ratings
Waterproofing doesn’t always mean watertight because modern waterproof fabrics use a semi-permeable membrane which allows for water vapour to be let out. This is called breathability, and means you don’t get wet with sweat. This is super important on the mountain because if you get wet, you get cold really quickly. As such, waterproof fabrics aren’t totally waterproof, otherwise you’d get damp and clammy inside regardless of the weather.
This is often a case of quality when it comes to the membrane. Higher quality membranes will be made with more care and better materials. In these cases, the micro-porous makeup of the membrane will be better structured for higher performance. As such, more waterproof membranes are more breathable because they’re just better quality!
DWR stands for Durable Water Repellent, and is a type of treatment applied to fabrics to enhance their wet-weather performance. They have a low friction coefficient which prevents water from holding on. Water will ‘bead up’ and roll off the fabric rather than sinking in. So DWR isn’t the same as waterproofing, as ‘waterproofing’ is handled by the waterproof membrane inside the fabric. But, DWR does help the waterproofing of a garment by preventing as much water reaching that membrane.
The seams are the weakest part of any garment, and is where water will get in because there’s a ‘gap’ in the membrane there. Taped or sealed seams means that a waterproof tape or substance has been applied to the seams on the inside of the fabric to make them as waterproof as the rest of the garment.
If your DWR has worn off, this can be replaced with spray-on or wash-in treatments by companies like Nikwax or Grangers. These can be bought online and easily applied for renewed performance. However, if your membrane is damaged via a tear or abrasion, then it cannot be repaired. Though, saying that, while you can’t repair a membrane, you can apply a waterproof patch to your garment to cover the damaged area. This is a good solution for small nicks or cuts where the rest of your garment is still functional!
Using the handy descriptions above is one way! Another way would be to check out the kind of riding or activity you’ll be doing, and then look for clothing suited or made for that. Backcountry gear will have high ratings, while park gear will have lower ratings. Gear made for the whole mountain will have mid-level stats. It boils down to how much you want to spend, and what you need it for. Reading descriptions, comparing products, and doing some research will help you get a handle on things. But for most resort riding, or vacation skiing and snowboarding, 15k of waterproofing and breathability is likely to be plenty!
Unfortunately, the waterproof rating of a jacket or pants is going to be directly tied to the membrane inside the fabric. As such, improving it isn’t really possible. Though it may be possible to apply a new or improved DWR treatment which could help! We’d recommend buying good quality gear suited to the type of activity you’re doing, rather than simply for looks or price!
Sweating is your body’s natural way of cooling itself down. While breathability is important, if your body is exuding so much moisture that it condenses right on your skin, there’s little that a breathability rating will do for you. Breathability only works with vaporised moisture, so once it’s liquid, breathability won’t help. If you find this is a problem, then experiment with layering, insulation, and ventilation to find the right balance. Layering and warmth are different for everyone!
In a word, yes. Higher ratings mean better performance. But high ratings usually come with a high price tag! Where you will find ‘value’ is individual, and again, dependent on your kind of riding or activity. If you need a super high rating, then can you put a price on staying dry? If you’re walking in the spring, or riding the resort on a ski trip, you’ll likely be paying for waterproofing you may not use.
Need to learn more about the waterproofing and breathability of Dope or Montec gear? Reach out to our CX team here for advice!
Related reading