What Does 2L, 2.5L and 3L in a Rain Jacket Mean?
So you're looking to buy a "waterproof" jacket for walking and hiking or maybe for running the trails. We've all seen a whole host of tech Jargon from manufacturers "explaining" in the loosest terms, the construction and waterproof capabilities of the jacket in question.
One common phrase you will see a lot in respect of waterproofing is that they are either 2L, 2.5L or 3L which simply means layers or ply. So let's try and explain what exactly those three descriptions mean.
DWR Water Repellence and Breathability
The first place to start is what you want the jacket for. No jacket has the capacity to do everything you need. Different jackets serve different functions so do pick the right one that suits your needs.
There are two core functions of a jacket:
1. Weather Protection
Clearly you don't need warmth in the middle of the summer when you are caught in a shower but by the same token, when skiing you are unlikely to ski in a thin L2 run jacket.
The second key element is that the jacket should ideally have some level of breathability.
This means that the material in the jacket is made in such a way so large water molecules can't get in but smaller vapour molecules, from your sweat, can get out. This vapour barrier is like a one-way street.
The layering of a jacket can be applied to any form of jacket so you will see warm wear L3 jackets as well as cool wear L3 jackets out there.
A jacket's rain protection will be denoted by parts per 000's to indicate how much water penetration you may get. The higher the number the more protection you should get.
This tech page focuses on purely the bonding of layers for weather protection and ignores the warmth aspects.
In terms of a rain jacket, it will usually utilise a breathable membrane such as Gore-Tex or Logic from ODLO. These are the breathable membrane technologies that get sandwiched between inner and outer layers to provide a one-way water barrier but are breathable allowing vapour and heat to escape.
This breathable layer is the 3rd layer in construction as it is a more costly production to insert that 3rd layer into the fabric shell.
2 Layer Jackets
When a jacket has two layers it means that the protective inner coating is bonded to a face fabric like Nylon or Polyester.
A 2L jacket is usually treated with a DWR coating on the outer shell. This provides what is referred to as Durable Water Repellency (DWR). DWR enables water to bead on your jacket and roll off and is usually applied using a chemical treatment although more and more manufacturers are using more Organically led solutions these days.
A DWR protective coating is usually used in conjunction with a breathable fabric like Gore-Tex. The purpose of the Gore-Tex is to stop water from getting into the interior of a jacket, whilst the DWR element aims to repel water from ever being able to penetrate the fabric in the first place. NOTE: DWR TREATMENTS WILL WEAR OFF! No avoiding it. But you can re-generate the DWR properties of a jacket with a wash in Silicone based solution such as Nik Wax or Storm. It's basically the same treatment you get on walking shoes and boots.
A 2L jacket therefore has two bonded layers as such. The outer fabric with the protective DWR coating and then an inner layer usually made with some kind of sewn-in lining like mesh or nylon.
As there are two layers, the jacket is usually quite flexible which makes is suitable for running or cycling although jackets of this nature are less breathable than 3-ply jackets and are as a consequence, less protective against wind and rain.
When a jacket is indicated as being 2.5L, the first layer employs a similar fabric as used in a 2 layer jacket, with a coating applied to the inside of that outer layer as the second layer. The half layer refers to a printed or sprayed-on partially protective layer that is applied over the second layer, all in all looking like one complete layer.
This sprayed on layer provides the DWR capability to enable the water to bead off your jacket and roll off.
A 2.5 layer jacket should be quite flexible and is very lightweight and often packable into itself and comfortable to wear. This option is probably the standard make-up of most good quality rain jackets.
A 2.5L jacket is less breathable than a full 3L jacket of course and won't provide the same level of defence that a 3L jacket would.
3 Layer Jackets
When a jacket is three Layer or 3L, it means that the membrane is laminated between the face fabric and a protective knit backing as opposed to on top of it as with a two layer jacket.
The jacket then has three layers as such, the outer fabric or Shell Layer, the protective coating in the middle usually a breathable membrane and then an inner layer usually made with some kind of sewn-in soft lining like Polypropylene mesh or Nylon. However it should all still broadly work, look and feel like one layer.
As there are more layers in the fabric, the 3 layer jacket is usually stiffer and crispier than 2 or 2.5 layer jackets as they usually have a "Hard Shell". Jackets made from 3 layers usually offer much better protection from the elements and they have a longer life but you should expect to pay for this quality. A 3L jacket is rarely packable so expect to either wear it or carry it!
The general rule for most average hikers in most situations is to opt for a standard rain jacket made with a 2.5 layer construction which in most cases should provide more than enough waterproof protection. The 2.5L jackets are certainly the most popular construction in most brand's ranges.
But you may require a jacket that takes a lot of punishment on a daily basis such as if you work outdoors and bad weather is a regular occurrence in which case an investment in the more expensive 3 layer might be the better option for you.
But be aware of one thing......there is no such thing as a waterproof jacket!
No jacket no matter how expensive is impermeable to water and even a 3L jacket will "Wet Out" at some point.
A jacket "Wet Out" happens when it ceases to vent enough heat and perspiration and the humidity on the outside is greater than the inside of your jacket. Unless you stop sweating and producing body heat which we don't advise as you'll probably die...........then this is a price you pay. Just control your layering to maximise comfort.
As a final note on that matter, how you protect your rain jacket, whether it's 2, 2.5 or 3 layer is critical to how long it will last. In short, look after it!
Most hikers should be fine with a standard 2.5 layer rain jacket. They're probably the most economical and you certainly get the most "bang for your buck"! You can check out some rain jackets here.
But if you have the money and you would like to invest in a really tough jacket that should last you a very long time then a 3-ply is a grand option. It will give you a lot of protection and the jacket will have a very long life. Remember though, none of them are invincible and if the rain is heavy enough you will still likely get wet at some point.