Waterproof Truths

November 9, 2008

Reading Time: 13 minutes.

I’ve been writing gear articles for magazines for years, covering almost all areas of technical outdoor gear and I like to think that I offer readers an alternative view on these subjects. Yet there is one red hot topic I’ve never really dared tackle: breathable waterproofs.


Well if you are potentially going to undermine one of the cornerstones of the outdoor industry you’re guaranteed to upset a lot of powerful people because many millions of pounds have been invested in the ‘waterproof and breathable’ concept and those advertisers who use such materials don’t take kindly to anyone undermining their message. What companies want are simple ideas that provide amazing results and, if neither is possible, then often the only option is clever marketing, which can take the complex ideas and mediocre results and give them some spin with a few good phrases, convincing diagrams and solid gold guarantees. Yet it’s not only down to the big manufacturers. 

On the other side, you have the bona fide users – the people who read this magazine. You can and do make your own judgments and aren’t tricked into believing the impossible is possible. This can lead to hostility towards breathable waterproofs, often with the greater the marketing the bigger the backlash, which is counterproductive, as people start talking about the stuff as if it’s made by the Devil himself (you’d imagine that George W Bush and Donald Rumsfeld were running the stuff up in Guantanamo Bay the way some people talk about it). The result of all this is that many users are just far too critical of these fabrics, meaning it’s often me who’s the one defending the companies who produce them, something I never thought I’d be doing. In a way, this article is just as much a defence against this criticism as criticism itself. The simplest thing would be to join these dissenting ranks by ranting on about how disappointed I am with shells, how they underperform, how I was led into believing I could be 100% comfortable and wasn’t and, in the process, champion the cause of the disaffected. Well, I’m not going to do that, because both the fabric manufacturers and their detractors only talk in extremes and absolutes and it’s time to look at the whole issue in a level-headed fashion and in doing so maybe find the middle ground.


Let me start by offering everyone the chance to dump their eVENT, Gore-Tex, Conduit and other types of breathable shells for a piece of gear which is everything you ever wanted in a shell. Light and compact, this beautifully simple piece of outdoor gear can be easily stowed away in a rucksack when not used or carried in the hand ready for instant action should the clouds open. It’s very cheap, ranging from a couple of pounds for a basic design, to maybe a hundred for a sturdy mountain model. It’s both 100% waterproof –even though the fabric is just uncoated nylon or polyester – and 100% breathable. At a push, you can use this piece of gear to protect more than one user, plus it’s also 100% UV proof, keeping you cool as well as dry. Guessed what it is yet? If I told you it could also be used to fight off rabid dogs and children, assassinate Bulgarian dissidents (actually they used a pin) and allow nannies to fly over rooftops, would you be any warmer? Yes, you guessed it, the humble umbrella – by far the best and only piece of outdoor gear that is 100% breathable and waterproof. Sure if it’s windy you might get a bit wet as rain is blown under its protective shield but no wetter than wearing a shell probably and I know it’s not ideal for mountaineering – after all, having one hand holding onto an umbrella may make climbing a tad harder – but if you want the ultimate in performance then that’s a sacrifice you’ll have to make because high performance always comes at a price – if it doesn’t then it’s simply just performance.

Why am I telling you this? Well, I believe that this is the level of performance users expect from modern fabrics, be they Gore XCR or eVENT or some super new wonder material. The reality is that once you put any kind of clothing on you are going to reduce your breathability, the greater the barrier/level of protection the lower that breathability becomes, whether it’s a jacket made out of newspaper or a pair of pants made from gaffer tape. So if an umbrella is out of the question and you have to use a shell, then here are a few new ways of thinking that may allow your shell to meet your expectations.


A shell must be waterproof

Pretty obvious really, but what does waterproof really mean? Well, there are several standards by which the term ‘waterproof’ is measured, designed to make sure that customers aren’t misled into buying products that ‘aren’t fit for the purpose’. These tests and standards are monitored and carried out by various bodies, be they CE, BSI or MOD, but all of them are based on water pressure tests on the fabric, basically increasing the water pressure until water molecules get through. Clothing manufacturers will also test these fabrics in their own labs, using long term testing (flex tests, abrasion, contamination, etc.) in order to see how they will stand up to long term use. The result is that when anything says that it’s waterproof, then it almost definitely will be.

Do they deliver? Yes, your shell should be so waterproof it can withstand the same water pressure as a nuclear submarine’s hull cruising along the bottom of the ocean, but the question is, is this a good thing, after all, do you need your shell to be that waterproof? Or to put it another way, your average shell is far more waterproof than your standard tent groundsheet, whereas a Paramo jacket – which thousands of users will attest to being the driest garment on the market – is, technically, as watertight as a sponge? The thing is that rain just isn’t as bad as all the manufacturers make it out to be, in fact, rain in itself is pretty puny stuff. Maybe it’s just part of the modern fear culture, but the rain has been built up all out of proportion as if even the slightest drop signals flash floods or The Day After Tomorrow special effects. This is probably due more to our modern way of living, which means we are barely exposed to the elements and the marketing which promises to protect us from this insidious moisture.

In fact, the actual number of hours spent in real rain for most outdoor people – ignoring showers, mist and fog – is actually very low and increasingly low what with global warming (perhaps the next big push will be on UV-proof clothing?). For those who climb in the Lakes (which has the highest rainfall in England at 330cm per year) this may sound like rubbish, but ask yourself how many times have you been out when it’s really been hammering down? Even when it does rain, those raindrops are actually pretty pathetic, hitting you at around 5mph (or about one metre per second) and although in really heavy rain they can reach 20mph, most of the time even a light waterproof layer is more than a match for this. What about if this rain is forced against the fabrics, such as when you’re wearing a pack, or if you’re sitting in a big puddle? A shell with very low waterproofing may well leak (i.e. Paramo), but this is offset by the fact it will then dry out faster. Even if rain is as bad as you’ve been led to believe, there is one thing that’s always going to be a top trump: your skin is 100% waterproof and breathable. If you accept this truth all of a sudden that dreaded rain isn’t such a big deal after all. What you need is a new mindset that buries the idea that water is bad and must be resisted at all cost, but one based on what to do when it does get in – because it always will. This is where one of the major obstacles to the waterproof-breathable concept lies, in that it builds up the shell as being the central component of your layering system when, in fact, it’s actually the least important, with the base layer coming first, followed by your insulation layers. This focus stems from the cost of these shell fabrics and because they’re worn on top, rather than underneath.

I have no doubt that although it would be possible to produce a base layer that would make shells almost redundant, to do so would be pointless – who would pay £200 for a thermal top? Due to this reliance on the sanctity of the shell, many people are unable to cope when it doesn’t deliver (we chill, we get miserable, we complain to the retailer) because they’ve put all their eggs in one basket and their primary layers only work really effectively when dry. Shell fabric manufacturers cannot trade on ‘we will keep you comfortable’ because they only sell part of a system, whereas people like Buffalo or Paramo can, as they sell an all-in-one system.


If we leave the fact that most of the water getting in is coming from you, not the weather, then there are a few ways it can get in. One of the factors in scoring a goal against your shell is the wind, which can accelerate the rain, snow or hail and blast you like a fire hose, which may force some water through zip flaps, down hoods and into pockets. Another factor is that your body creates holes for the weather to sneak through, sending it cascading down your wrists when climbing, down your neck when looking up etc. If you were making shells for snakes, it would be easy, as they would only have one opening (although you would still have trouble with the drawcord), but human anatomy just makes for leaky clothing. This problem is designed out in survival clothing, or for activities where the maximum temperature must be maintained (due to the fact that heat cannot be generated easily, or because the water is so cold as to overpower the insulation worn underneath), but for outdoor use rubber seals would just be impracticable because 99% of the time it’s not the rain that’s the problem. Also, the fact that you’re probably wearing wicking layers means that moisture may wick into the shell as well as out of it, soaking up sleeves, down necks or from sweat-soaked backs. One other reason for leakage is that waterproof fabrics do wear out or may be faulty (bored or brain dead shop staff stick security tags through the middle of jackets, for example) or the membrane or coating may not have been correctly applied, being too porous and just letting the water through. In fact, there are many people out there with 20-year-old Gore jackets that are undoubtedly no longer waterproof but seem so because rain is just so rubbish, or because in reality they never use it in aggressive weather.


The most classic outdoor clothing you can buy is heat porous (Polartec 200 fleeces, Powerstretch, woolly jumpers) meaning that air held within its construction is not locked in, so convection (wind) will move this heat away into the atmosphere. By placing a windproof barrier over this clothing, you effectively reduce outside airflow, greatly increasing your clothing’s heat stability and warmth. As far I know there is no standard for windproofing. Does it deliver? A shell does this well, and this is perhaps the role it fulfils most of the time for most users, keeping their insulation stable, along with repelling the odd shower. The question is, are they taking a sledgehammer to crack a nut? Do you need something with such a high level of waterproofing to do this job? In fact, as most users of wind-resistant mid-layers know, using such layers means you don’t need to depend on your shell as much, saving it 10% of the time when a lighter top can’t cope. Doing this means that you can reduce the weight, bulk and price of your shell and perhaps even increase breathability in the process.


Firstly the word breathable is worthless, as fabric –unlike humans and wine – does not breathe. Fabric may be able to transfer moisture vapour (trendy three-letter acronym coming up – MVT – moisture vapour transfer) from the inside to the outside through some process, but unlike a pair of lungs, it cannot suck out the moist air and replace it with dry air – even though over keen marketing people would like to make you believe it can. There are CE standards by which you can measure breathability, but unfortunately, it seems that fabric manufacturers choose the ones which show the best results for them and again, like the waterproofing tests, these tests are lab-based.

Do they deliver?

How much more breathable are these fabrics compared to non-breathable? Well, I don’t believe most of the tests I see as they are based on lab testing, so a while back, I decided to do my own little test. I took a non-breathable waterproof, and an old breathable waterproof cut them both in half and sewed them together. I then used this several times, on all occasions trying to dress accordingly to reduce the chance of sweating. The first thing was that the non-breathable side quickly became sweaty – although, with good layers underneath, this wasn’t too uncomfortable. The breathable layer stayed mainly dry when not active, but once I began to move some moisture did appear, but again wearing the right clothing underneath made this bearable. The big difference was that the breathable side would eventually dry out, as the warm but damp insulation dried and pushed the moisture out of the shell. The nonbreathable side, on the other hand, held the moisture in the fabric and it was only able to dry out when taken off. This test showed that the breathable side was only perhaps 20% more breathable, but this was offset by the fact that this breathability gave the fabric the ability to bail out the sweat – which is vital for extended wear. But how big a problem is this?


Just as you need to accept that rain will get in your shell, you also need to accept that you will get sweaty. Your skin temperature is 34°C and when it reaches 37°C (core temperature), receptors signal that you’re getting too hot, with the result being that you begin to sweat. Sweat is produced so as to increase evaporative heat loss and so cool the body. If you’re walking naked from John o’ Groats to Land’s End without anything but your trusty umbrella, then this works brilliantly, as the light wind takes away the heat of your sweaty buttocks and you cool off. If, on the other hand, you’re wearing a typical layering system of a base layer, fleece and shell, conductive heat loss from all body parts that are covered can only happen by the sweat soaking into the fabric and lowering its insulation properties – a very slow and dangerous way to lose heat. Ideally, this sweat will also be moving out along with this heat to your shell.

Now before I continue, say the word ‘sweat’ and see what images it conjures up? Are they positive – like when you say taste, touch or smile? Or are they negative, like the words puke, thirst and hunger? Like rain, sweat has been much maligned and used to scare us into believing that we have to rid ourselves of this terrible stuff at all costs. In fact, sweat is just the body’s way of telling you that you’re wearing too many clothes and that it’s looking at a loss of performance if you don’t do something about it. It’s no different from your body telling you it needs a drink by signalling that it’s thirsty. Like thirst, sweat is an important signal, but we’ve been educated to view it as a nuisance and led to believe we can engineer it out of the equation when most of the time we just need to take some clothes off.

What if someone invented a gadget that stopped us from getting that horrible thirsty feeling? People would die because they didn’t hydrate. Yet many people in the outdoors ignore their sweating and end up getting hypothermic. So this sweat is being pumped out into your clothing and ideally, via the process of capillary action, moved out towards your shell. If the sweat isn’t able to escape, it will build up and saturate your insulation, causing conductive heat loss to increase (wet fabric conducts your heat 25 times faster than air).

Once this heat loss allows your skin to return to 34°C you will stop sweating, but the conductive heat loss will carry on and so it’s the next-to-the-skin fabric’s ability to stop conduction that proves vital, otherwise, your temperature will continue to drop (causing you to put on more clothes or increase energy output). So your shell is there to ‘get rid of the sweat’. But how important is the shell in doing this? I’d argue again that you need to put the shell to the bottom of the pile and look at your base and mid-layers first when it comes to being ‘dry’, after all, dryness is measured on your skin, not on the inside of your shell. You need to look at how the combined insulation of your layers will work over the full spectrum of energy expenditure and temperature.

The typical baggy, long-sleeved base layer and equally baggy fleece (Polartec 200), worn beneath a shell, is totally useless for any performance activity, in my opinion, generally leading to overheating and chilling. The problem is that standard weight fleeces may make great leisure jumpers, but for active use they give far too much insulation, creating a very hot and sweaty microclimate. Your base layer should provide minimal actual insulation (being low density and thickness), with the ideal being – dare I say it – a string vest (look at Brynje underwear). That isn’t to say that this layer shouldn’t be warm, but this warmth comes from the fact that it isn’t conducting your heat away from you – as it’s the insulation layers that should do the real warming). Building up a good ‘comfortable and cool when dry’ yet still ‘warm when wet’ is the ideal system for active use.

The term ‘system’ shouldn’t give the impression that you get one clothing system that covers any eventuality – the most important thing is to regulate it so that it works. As for suggestions – having a very thin but close-fitting base layer is ideal, as this kind of fit will speed up the base layer’s drying speed helped by its low water-holding ability. The insulation piece you wear should be ‘active insulation designed to maintain a comfortable skin temperature yet be able to dump the heat before overheating (full zip, sleeves that can be pulled up to your elbows). A very thin windproof micropile top (Marmot Driclime, Rab Vaporise etc.) is ideal for this, creating a true softshell, worn as both the base and mid-layer – which makes heat dumping easier and the chance of overheating much lower.

A secondary insulation piece held in reserve for ‘passive insulation’ is also required – perhaps a thin, high loft, shelled ‘puffball’ type synthetic duvet, which would be worn when static, or when warming. This type of clothing puts much lower demands on your shell – it will increase the shell’s effectiveness in many ways – plus is much more able to cope when moisture does appear within the shell (the speed bump concept), either stopping it from getting any further or keeping you comfortable and drying quickly if it does.


Your shell’s fabric should be able to keep out most of what the weather throws at it – but you can’t depend on its moisture vapour transfer getting rid of everything you throw at it from the inside. So what do you do to extend or improve on the results you can expect from its 20% breathability?

Don’t wear it: Pretty simple really, if you have the right layering system, then your dependence on your shell is much reduced. Think back to those days before modern shells to the age of neoprene and PU cagoules; people just didn’t wear them unless they had to (they wore cotton or nylon windproofs unless it was raining). Remember that even the most breathable shell isn’t actually that breathable, yet people wear them all the time. Learn to vent your exertions – Heat rises, and so does the moisture it contains. That’s why the top half of your shell is always much sweatier than the bottom half. Ideally, you should try to play on this effect, unzipping the neck slightly and loosening your chest strap so that the shell can billow out and the moisture escape. This is one good reason for wearing a Tilly type hat, as you can leave the neck of your shell open without worrying too much about water getting in (which, of course, would increase the moisture level within the shell). It’s often advised to get closer fitting shells, as they help to increase the moisture differential (the same amount of moisture but in a smaller space) but having a looser style can also help to get rid of moisture as convection plays a bigger part, especially with a bit of manual pumping of the chest fabric, which will expel the moist air. It also may sound obvious but just unzipping your jacket for a few seconds and letting the wind in can dump a lot of that troublesome moisture. Pit zips, although much maligned, can provide an escape route, but because the moisture rises you are probably better off unzipping your neck a few inches and using a jacket with very large, vented pockets.

Strip off: The clothes you’re wearing are probably about right for your current exercise before it’s raining, allowing your body to remain at a comfortable temperature. When you throw on your shell, you’re effectively pushing your insulation level to a point where you cannot help but sweat (unless you slow down). This is very noticeable if you’re wearing heat porous mid-layers as the lack of convection will increase the insulation dramatically. If, on the other hand, you’re wearing thinner, more active layers that are already windproof, then the insulation difference may be much smaller.


When I first got into the outdoors, I was a serious Buffalo user and thought all shells were evil and the people who used them weak and pathetic. I was, in fact, one of those radical doubters as far out in my views as the global marketeers. Now I can see the advantages of shells and how, when built into the right system, they can prove vital in staying comfortable. The leaps in fabric technology have never been as great as we were led to believe, but the leaps in design and engineering have. These days we can buy 100% waterproof shells that weigh very little, with seams that are welded and with face fabrics that are both tough and water-resisting. Hoods are better, pockets are better and so are zips, the cord pulls and every other component. As outdoor people, we are spoilt for choice, and although maybe they aren’t as breathable as an umbrella, they are a dammed sight more practical.