Knowledgebase Page - Choosing a Shell Jacket

Oct 11, 2023

Choosing a Shell Jacket

Select Your Activity

If you want a jacket to keep you dry when running, this will be a very different jacket to one suitable for backpacking or trekking.


Waterproofs designed for running will be very lightweight so that they won't slow you down. It needs to pack very small so you can carry it when you don't need it, and the best examples will be highly breathable. Also, consider a smock to save weight.

A Backpacking Jacket needs to be quite durable and probably won't be the lightest jacket in the range. The reason is that you will have hip-belt and shoulder straps pressing down on the fabric forcing water through it, and if they move as you walk they will wear the fabric.

Waterproof Jackets for general purpose use will probably be mid range in terms of weight (400-500 grams) because of durability ad have a wide range of pockets to suit all tastes. Winter weight shell jackets need to survive a Scottish whiteout with hail like bullets! You can get away with lighter weight jackets but you can't beat the protection of a category heavyweight at around 550-750 grams.

Choice of Fabric

There are three characteristics to consider when choosing a jacket based on its fabric, Waterproof Performance, Breathability and Durability. Lighter weight jackets will be a compromise on durability and heavier jackets are often less breathable. Waterproof performance is crucial, but the highest-rated waterproof jackets may not be necessary for your activity. Breathability often becomes the most important characteristic if the jacket is for Adventure Racing when the user will be running or walking fast uphill.

- You can use this waterproof performance is usually measured by Hydrostatic Head (HH), this is a measure of how much pressure there needs to be for water to penetrate the fabric and is expressed as a water column in millimetres (mm). The higher the figure the better the performance. Typical figures range from 10,000mm to 30,000mm... Read more about Hydrostatic Head.


- Branded fabrics dominate the production of waterproof shell jackets, The most common fabrics are Gore-Tex, eVent and fabrics by Polartec and Pertex. There is also a full range of in-house fabrics by key brands such as Haglofs, Marmot and Mountain Hardwear. We research the fabrics and where possible quote the key statistics for Hydrostatic Head and Breathability - the combination of which should allow the comparison between garments - however, remember the rating given is for the fabric, not the jacket - so a jacket with a load of pockets may be less breathable than one without even if the fabric statistics suggest otherwise.

- Breathability is usually measured in Moisture Vapour Transmission Rate (MVTR), the higher the value for MVTR the more breathable the garment is... Read more about MVTR and Breathability.


- Durability is partially a function of weight - heavier jackets will tend to be heavier because they have a heavier and more durable face fabric. This is true when comparing a 200gram shell with a 400gram shell - but if the weights of the garments are close to each other the extra weight may be due to features and not due to a hardier fabric. Some jackets have patches of more durable material where rucksack hip belts and shoulder straps make contact, thus keeping the garment lightweight but adding durability. Also, 3 Layer fabric will be more durable than 2.5 Layer.


Hoods: A well-designed hood is critical if you will be using one often. Many are helmet compatible, which means they can be large, but this need not be a problem when you are not wearing a helmet if the adjustment of the hood is good. Look for a 'round the head' cinch cord which, when tightened grips your head so that when you turn - so does the hood. You should also be able to cinch the hood around your face for windy conditions and it should have a peak. Peaks can be 'soft foam' or quite stiff with a wire brim - the wire enables you to set the peak shape without it moving, this is the best type - but on the lightest jackets, a foam peak will work quite well if the hood is cinched in.

Pockets: The pocket arrangement that will be best for you will come down to personal preference but there are a few things you should take into account. More pockets will reduce the breathability of the jacket because there are more layers of fabric for perspiration (in the form of water vapour) to get through. Jackets designed for high-energy activity will often have pockets lined with mesh - this is to maximise the breathability of the jacket without allowing the pockets to compromise its performance.


Also consider how much you will use pockets - if you're wearing a shell jacket then presumably it's raining, therefore it's unlikely you will be putting your hands into your pockets other than to get things in and out. Also pockets around the hip area will be inaccessible if you are wearing a rucksack hipbelt so they are not necessary - more useful will be 'Napoleon' chest pockets which open vertically either side of the main zip. It's just these pockets that I normally use - with most rucksacks having some pockets accessible whilst on the move there isn't masses of gear to put in jacket pockets - I normally limit it to compass, gloves and a hat at the most.

Zips: Will either be the water resistant type or will be protected by a flap. If a jacket has the water resistant zips as the main zipper it will usually have a flap inside as extra security against water penetration. Older designs have an external flap secured with velcro - these are effective at keeping water out but add a lot of weight and are not necessary.


Pit Zips: Some jackets have Pit zips - these are under the arms and can be used to ventilate the jacket while limiting the exposure to rain. Its surprising how little water gets in even with pit zips fully open - the underarm area is a great place to vent excess sweat.

Cuffs: Require some method of closure, this is usually velcro, or it maybe just gathered with an elastication in lighter garments - the important thing here is that the fabric is gathered round the wrist to minimise water wicking up the arm.

Size & Cut

- Shell jackets are sized to fit over midlayer garments - so you should buy your normal size - it shouldn't be necessary to buy a 'size larger' to accommodate a fleece underneath. Having said that most garments will also have 'Fit' information as well as a size chart. Garments designed for running or moving fast will have an 'Athletic' fit or 'Slim' fit (manufacturers use different words) because the wearer is not expecting to be wearing much underneath.

- More traditional shell jackets will have a 'Standard' fit, or 'Mountain' fit, which will allow more space for midlayers.

If you want a jacket to keep you dry when running, this will be a very different jacket to one suitable for backpacking or trekking. Waterproofs designed for RUNNING will be very lightweight so that they won't slow you down. It needs to pack very small so you can carry it when you don't need it, and the best examples will be highly breathable. Also consider a smock to save weight.