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Thursday 21st June 2007
Introduction
What jacket should I buy?
Snow sports
Mountaineering / winter climbing
Moderate outdoor activity
High aerobic activities
Making a final selection
How waterproof is ‘waterproof’?
How breathable is ‘breathable’?
Durable Water Repellency (DWR)
Fabric testing information (technical)
Mountain marathons, adventure races, backpacking, alpine climbing, skiing, mountain biking, mountaineering, or simply walking the dog – all have different requirements that will affect your clothing choices. So if the time has come to get a better waterproof, how do you choose from the myriad products now available on the highstreet and internet?
This article is designed to help you make an informed choice. It focuses on jackets because this will probably be the main waterproof purchase you make. However, a lot of the information provided here is transferable to other garment purchases such as overtrousers and gloves. More specifically, this article will help you:
What Jacket Should I Buy?
This article only deals with jackets considered ‘hard shells’ that are fully taped. While there are several ‘soft shells’ that would be more than adequate in wet weather, let’s keep this guide simple for now.
If you take part in outdoor activities regularly throughout the year, you need to consider buying two or more jackets: one for fair weather, generally light, simple, breathable; and a more substantial jacket for longer use in less clement conditions (rain, wind, snow), such as for winter walking and climbing, or skiing.
It’s not uncommon for people to own five or more waterproof jackets (one for every occasion!) especially if you work outdoors. However, for most people two will suffice – you just have to compromise in some situations! So, first of all, think about what outdoor activity you enjoy the most, how often you do it, and then consider what you can afford.
If you can only afford one jacket for the time being, or you are relatively new to outside adventure, go for a jacket that will protect you against the worst weather you’re likely to encounter. If that means wearing a top-end jacket to stroll to Tesco, then fine, but at least when you go on your annual winter pilgrimage to the Scottish Highlands, you will be sufficiently protected from the elements.
If the only activity you do outside is skiing or snowboarding, then buy a dedicated winter sports jacket, pants and gloves. But select garments that are still waterproof… Just because you’re going skiing doesn’t mean it won’t rain, and sitting on a chairlift is miserable if you’re wet. Skiing or snowboarding clothing may not need to be as breathable as for hill walking, but it will still require good durability from falls, and close encounters with sharp ski or snowboard edges. Perhaps some integrated insulation, a pocket for lift pass, goggles or snacks, and a snow-skirt to stop powder and drafts reaching your lower back. Packability is not such a problem, because unless you’re skiing in spring-like conditions, you will be wearing it all day.
Mountaineering / winter climbing
Generally, mountaineering or winter climbing will require a garment that is a balance of high waterpoofness, breathability and durability. This is especially important if you are in a remote area, or exposed for long periods without shelter. Might you be on a high mountain plateau, or wading through snow, or battling up a Scottish gully with spindrift whipping into every crevice? Other questions to ask yourself are:
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The great thing about top-end mountaineering jackets is that they offer the best outer shell protection available. But the disadvantage of all this armour is that they tend to be heavier/bulkier and therefore less suited to fast-paced activities where ‘light is right’, such as adventure racing and mountain biking. There are lightweight mountain jackets available of course, but this will mean compromising on some features such as durability or the number of pockets.
Look to spend in the region of £150–£300
Hill walking, hiking, trekking, rambling… All outdoor folk are likely to do a bit of this – i.e. travel in non-urban areas with few opportunities for shelter or to dry off. For this purpose, your jacket needs to be waterproof and breathable enough to maintain comfort all day. On multi-day trips, you may only have one set of clothes so it is vital that you stay as dry as possible – and that means dry from sweat as well as from rain! An entry level waterproof may be fine for popping to the shops/pub or walking the dog, but if you get wet on a mountainside your body heat will escape 25 times faster when you’re wet. Best outcome, a miserable day, worst outcome, hypothermia.
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Moderate activity: Marmot Women’s Cloudlight Jacket |
The key point about this type of jacket is that it is fairly light and packable enough to carry, yet substantial enough to offer suitable protection for the worst weather you’re likely to encounter. Breathability is still very important in this category, especially if you like to slog up big hills! But if you just need the jacket for easier walks where you are unlikely to perspire much, then there is no need to go overboard. Equally, if you only hill walk in reasonable summer weather then you can get away with something even less substantial (see jackets for high aerobic activities, below).
Price varies immensely depending on what conditions you’re protecting against, but, generally speaking, expect to spend £70–£250
If you’re the type of person who can’t sit still then you need clothing that’s extremely breathable, lightweight, easy and comfortable to move in, simple and compact. Jackets for ‘high aerobic’ activities are stripped to the bare essentials, and can easily be stored in your pack until needed. They provide adequate protection from showery rain, or in situations when shelter is not far away, but the downside is that they are not as durable. And bear in mind that when you’re whizzing around, even the most breathable waterproof jacket in the world can’t keep up with the rate of moisture evaporation from the human skin.
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Lightweight jackets are also popular with day walkers and summer backpackers, who might have no intention of being in the rain but sometimes get caught out. A word of warning though – if you choose this over a dedicated hill walking/mountaineering jacket, when the heavens open, don’t expect it to offer the same protection!
Though lightweight, breathable fabrics can be expensive. Because these jackets are stripped down, expect to pay only £60–£140. Paying more money does not necessarily mean it will last longer!
Making a Final Selection
Ok, let’s say you’ve identified two jackets that have the characteristics you want… but how do you know what one will perform the best? If they both claim to be ‘waterproof’ and ‘breathable’ why does one cost three times as much as the other?
When buying a waterproof it’s no good asking simply ‘is it waterproof and breathable?’ because the answer will invariably (in quality outdoor stores) be ‘yes’ to both the £50 jacket and the £300 one next to it. However, quality of build and features aside, the price difference is influenced greatly by how waterproof or how breathable it is…
How waterproof is ‘waterproof’?
For a jacket to be deemed waterproof, the fabric and seams must keep out a minimum amount of water in laboratory conditions. Depending on the test method, the results are shown as PSI (pounds per square inch) or mm (millimetres) of pressure. For more information on tests go to the Fabric Testing Information section below.
All garments sold in the UK that state they are waterproof have had to meet the British Standard of 3 PSI, which is approx 1,500mm of pressure. Falling rain generates about 2 PSI (approx 1,000mm), however an 84kg person can generate about 8 PSI (4,000mm) when sitting and 16 PSI (approx 8,000mm) when kneeling, so your bargain waterproof may not be as waterproof as you think!
Marmot set their minimum at 20 PSI (10,000mm) and so should you. For more extreme, windy and extended conditions adjust that to 40 PSI (20,000mm).
Bear in mind that keeping out the rain is more down to the design of the jacket, rather than how much water pressure the material can withstand. So even a 40 PSI jacket is no good if rain easily seeps in through the main zip! Always ask yourself: Are any zips exposed? Can the hood be adjusted to help prevent water going down your neck or absorbing into your hair? Can the cuffs be adjusted? Are the seams sealed in some way?
How breathable is ‘breathable’?
Staying dry is not just about keeping the rain out, it’s also about letting water vapour escape. In this context, breathability is the ability of the fabric to transfer moisture vapour (not air) and is generally stated in terms of:
The human body can expel over 4 litres of moisture a day – you just don’t notice it until you wear a significantly less breathable material over your skin. The best breathable yet waterproof barrier is perhaps human skin; it stops fluids getting in, yet opens up when fluid needs to get out. The higher the activity/aerobic level and outside temperature the more the body sweats, so the more breathable your jacket needs to be. Just remember that even the most technologically advanced garments will not be as efficient as human skin at transporting moisture away.
High activity outdoor sports like trail running, cross-country skiing, mountain biking and mountaineering require a breathability performance of at least 20,000 gr/24hrs/m² (≤6 Ret). So go for jackets that have a Gore-Tex XCR (2 and 3 layer) or Marmot’s own, more affordable MemBrain 2L. If however, weight and packability take precedence, coated technologies such as Marmot PreCip Plus (e.g. Marmot Essence Jacket) or Gore’s own Paclite are your best bet.
Activities that produce less heat, such as walking, climbing, and lift skiing, need breathability in the range of 10,000 to 20,000 gr/24hrs/m² (6 to 13 Ret) – though, generally speaking, the more breathable, the better! Buy the most breathable you can afford; jackets with Marmot’s PreCip coating are good choices for those on a budget.
Marmot do not recommend buying anything less breathable than 13 Ret unless your hobby or work involves standing still.
Also, bear in mind that all technologies mentioned so far will have a range of performances due to variations in the face fabrics they are applied to. Furthermore, jackets with a liner either bonded or hanging loose on the inside will in fact be less breathable, but give the impression they are better because the fabric soaks the moisture away from your skin.
Tip: To help minimise moisture buildup under your waterproofs, use your vents and front zippers to allow moisture vapour to quickly exit your clothing system. Think about the layers you have underneath, and perhaps take one off (remember, sweating is your body’s way of getting rid of excess heat). Alternatively, think about slowing the pace down a bit, or anything to reduce perspiration rate.
Durable Water Repellency (DWR)
DWR is an often overlooked but extremely important feature in the performance and comfort of rain gear. DWR is a chemical treatment that bonds to the outer material and increases the surface tension so that water droplets bead up and roll off your garment. It does not make your garment waterproof, but it can affect your comfort by providing a buffer between the inside and outside of your garment. It reduces condensation on the inside and aids in water vapour transfer.
If a fabric does not have a DWR finish, or the DWR is no longer working, water will saturate the outer surface making the garment feel cold with increased condensation. Sometimes this cold feeling makes us think the jacket is leaking, when in fact it is not. The DWR finish can be affected by: washing, dirt, oils, smoke, and other contaminants. These contaminants will ‘mask’ the DWR and break down the surface tension of water droplets, allowing them to penetrate the outer textile. To rejuvenate the DWR, wash your jacket with a dedicated outdoor garment cleaner (as regular detergent is anti-DWR!) and put into a medium heat tumble dryer for about 20 minutes. The heat is necessary to ‘refresh’ the DWR and get it working again.
With time, it will be necessary to reapply the DWR. Granger’s makes some excellent DWR products. Go for the spray applications as opposed to the wash-in product, especially if you have a wicking lining in your garment (a DWR layer on the inside will turn your wicking lining into a water repellent lining, just the opposite of what you want!).
Fabric Testing Information (technical)
For most of you, the information above will be enough to help you make an informed purchase. But to learn more about how some manufacturers test fabrics and about specific treatments used for waterproof jackets, read on!
No lab test will replicate exactly what a jacket undergoes in real life situations. However, they do give a general indication of final performance which can be illustrated numerically.
Waterproof test:
Warning: not all test methods are the same, even though they show results in PSI or mm. The best laboratory based test currently is the hydrostatic head test. Either ISO 811, BS EN 20811 or Japanese Industry Standard L-1092 (virtually identical) or the British Standard Suter Test / WEP (Wet Entry Pressure) test – similar to the aforementioned tests, but with a very low increase of water pressure.
Hydrostatic head test: Simply stated, it is where a sample of the fabric is spread over a hollow cylinder. Water is then pumped into the cylinder below until the water pressure is high enough to come through the fabric.
Breathability test:
There are several different ways to test breathability of a waterproof garment. The main ones you will come across are the Upright Cup (A), Inverted Cup (B), and the Ret test. It is important to note, however, that the results do not correlate with each other and therefore this should be taken into account if you are comparing jackets that have been tested in different ways. This is because it depends on the type of coating or lamination and how it moves the moisture. Typically, hydrophobic coatings perform better than hydrophilic laminations on the A1 test, and visa versa for the B1 test.
The Upright Cup (Japanese Standard Test L-1099 A1) method: A desiccant, calcium chloride, is put into a cup (to absorb all moisture). A piece of the test fabric is then secured over the cup and placed in a controlled environment. Then after period of time the cup is weighed to see how much water has been ‘pulled’ into the cup through the fabric. The weight is then extrapolated to show the number of grams per 24 hours per sq metre (gr/24hrs/m²) of fabric that will pass through the fabric.
The Inverted Cup (Japanese Standard Test L-1099 B1) method: Simply stated: A desiccant, potassium acetate, is put into a cup and sealed with a piece of ePTFE (expanded polytetraflouroethylene). ePTFE is waterproof and extremely breathable so that it has a nominal effect on the test. The test fabric is then placed over the cup with the fabric side to the cup. The cup is then inverted into a pan of water. Then after period of time the cup is weighed to see how much water has been ‘pulled’ into the cup through the fabric. The weight is then extrapolated to show the number of gr/24hrs/m² of water vapour that will pass through the fabric.
| Performance range | Upright Cup – A1 | Inverted Cup – B1 (gr/24hr/m²) |
| High | >10,000 | >20,000 |
| Moderate | 4,000–10,000 | 10,000–20,000 |
| Low | <4,000 | <10,000 |
Warning: The USA ASTM test method for Upright and Inverted Cup has many versions which will have significantly different results for the same fabric. The Japanese Industry Standard Test is currently the most reliable but unfortunately it will be almost impossible to find out from the retailer even though it can make a significant difference to the result.
Ret test – Resistance to moisture vapour transmission – Sweating hot plate ISO-1092:
Since the protocol of the Ret test method includes the comparison of laboratory data to the perception of comfort by people actually wearing the garments and exercising on a tread mill, this is probably the most reliable for the comparison of fabrics and the prediction of comfort in the field. To do the lab test a fabric is placed above a porous (sintered) metal plate. The plate is heated and water is channelled into the metal plate, simulating perspiration. The plate is then kept at a constant temperature.
As water vapour passes through the plate and the fabric, it causes Evaporative Heat Loss which cools the metal plate and more energy is needed to keep the plate at a constant temperature. Ret is calculated by how much energy it takes to keep the metal plate at a constant temperature. The more energy it takes, the more evaporation is taking place and therefore less resistance in the fabric to moisture vapour transmission. Less resistance = more breathability.
Ret 0–6 | = Very good or Extremely Breathable |
Ret 6–13 | = Good or Very Breathable |
Ret 13–20 | = Satisfactory or Breathable |
Ret 20–30 | = Unsatisfactory or Slightly Breathable |
Ret 30+ | = Unsatisfactory or Not Breathable |
All Marmot fabrics perform at the Very Breathable rating or better. Whilst there is not a direct correlation between any of the tests, Marmot have found that fabrics which perform well on the Ret and B1 test have better field test results and more happy/comfortable users.
To see technical diagrams of the three breathability tests described above, click here.
DWR Testing:
Water is sprayed onto the garment’s outer surface. In the ‘Spray Test’ the first number indicates the amount of water sticking to the surface:
100 (ISO 5) – No sticking or wetting of upper surface
90 (ISO 4) – Slight random sticking or wetting of upper surface
80 (ISO 3) – Wetting of upper surface at spray points
70 (ISO 2) – Partial wetting of whole of upper surface
50 (ISO 1) – Complete wetting of whole of upper surface
0 – Complete wetting of whole upper and lower surfaces.
The second number is the number of washings; so, for example, 80/20 means that after washing the garment 20 times, the upper surface at spray points was wetting out.
Don’t get too hung up about one DWR being better than another when choosing a new waterproof. There are far more important factors to consider first. Any decent waterproof will have a satisfactory level of DWR which can be rejuvenated (or in some cases improved) to a certain extent anyway.
Field testing:
There is only so much a lab test and personal testing one can do of course, so Marmot have been sending their clothing and equipment to mountain guides and outdoor adventurers across the globe since the 1970s – from grass roots hill walkers to cutting edge mountaineers. Lab testing combined with user feedback ensures that Marmot kit works, it lasts, it’s easy to use and it looks good of course!
For further information on Gore-Tex technologies:
www.gore-tex.co.uk
For further information on Marmot Outdoor Clothing & Equipment:
www.marmot.com
For information on how to care for your waterproof:
www.grangers.co.uk
www.k2-uk.co.uk (specifically here)
Copyright © 2008 planetFear. All rights reserved. |
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