Waterproof technology

Well Summer is on its way out and Fall is waiting in the wings, bringing with it the likelihood of wet, rainy conditions. So it is time to dig out those rainshells, rain pants and waterproof shoes and boots again. Or maybe its time to upgrade or replace your old ones. We get lots of questions in the store about waterproofs so I thought now would be a good time to look at the different technologies available to keep us dry while enjoying the great outdoors here on the Island.

Waterproof layers have to have two functions, firstly to keep us dry on the outside and secondly to keep us dry on the inside. If their sole function was to keep us dry from rain falling on us we could simply make a layer out of thick plastic and we would be kept dry from the rain. Plastic unfortunately doesn’t allow our sweat to escape and so as soon as we started being active we would get wet from the inside. This ability to allow moisture caused by perspiration to escape is known as breathability. Lightweight rainshells can improve breathability in their construction by the addition of pit zips or torso zips, by having pockets made of mesh so that when the zipper is open air and moisture can escape from the jacket. But the most dramatic increase in breathability comes from the material that is used in the construction of the jacket.
Before we get into the different technologies lets just examine one technology that all rainwear has in common and that is a Durable Water Repellancy (DWR) finish that is applied to the outside of the jacket. This is a chemical treatment that causes water that lands on the jacket to “bead” or to form a droplet that will fall off or can be brushed off to allow the outer fabric of the garment to stay dry.

This DWR treatment is the primary barrier to rain and if maintained helps to improve the garments breatheability. However over time this DWR finish will break down and cause the outer fabric to absorb water, or wet out. If this happens the breatheability of the garment will fall and you will start to get a build up of moisture inside the jacket making people think that their jacket is no longer waterproof. So it is critical to maintain this DWR finish by periodically cleaning the jacket with a suitable cleaner such as Grangers cleaner and then reapplying the DWR finish with a wash in or spray on treatment like Grangers proofer. Washing the garment in regular detergent can strip off this DWR treatment.

Ok so why are some rainshells 3 times the price of others? This comes down to the materials and technologies used to make them. All rainshells will have a facing fabric, the outside layer that has the DWR finish applied to it and this is there to give the jacket its durability. More expensive garments will have a heavier but more durable fabric on the outside and this makes them suitable for mountaineering, climbing, backcountry skiing and bushwhacking where a lighter fabric would be in danger of being ripped or torn.

The part of the garment that alters the performance and price of the garment is the next layer. This is the waterproof/breathable layer and it may be applied as a laminate or as a coating and we’ll now look at these in more details.

The waterproof breathable component of a rainshell is made up of an ePTFE or PU derived material and it can be found either as a laminate, a separate layer applied to the inside of the outer fabric or as a coating to the back of the outer fabric. If it helps think of a laminate as wallpaper applied to a wall and a coating as a layer of paint applied to the wall. Laminate construction is usually found on more expensive pieces and coatings generally on lower price point pieces. Examples of a coated layer would be The North Faces Hyvent material and examples of a laminate would be Goretex, eVent or Polartecs new Neoshell. The waterproofing abilities of both laminates and coatings are pretty similar but the laminates generally have the higher breathability ratings. At present there is no industry standard to compare breathability ratings and you may see seemingly impressive numbers given for how breathable a jacket is 10-20,000 being typical but that doesnt mean that a 20,000 jacket is twice as breathable as  10,000 jacket as the numbers may be been derived by different testing conditions, however it may be an indication that one jacket is more breathable than another. The breathability of most jackets is based on the membranes ability to transfer smaller water particles from the inside to the outside without letting larger rain drops  come in, to do this there has to be a temperature and pressure gradient across this membrane which causes the inside of the jacket to get warm and damp at times. Some newer fabrics, such as Polartec neoshell are more air permeable allowing the material to breathe without needing to build up that warm perspiration climate inside the jacket and the manufacturers claim improved breathability over other materials. However the downside is that these jackets are not as effective at blocking the wind as a traditional laminate.

The construction of the garment, as well as the membrane used, will affect the price of the garment. There are 3 basic constructions. The cheapest uses a 2 layer make up, here a coating is applied to the outer fabric making one layer and then the second layer is a hanging layer often a mesh material to protect the membrane. This mesh layer can bunch up and also makes the garments heavier. The most typical construction method is a 2.5 layer. Here the lightweight outer fabric has a second layer applied to it, typically a PU based coating and then this is overlaid by a very thin layer often in the form of dots or a patterned film that protects the membrane material. These garments tend to be lightweight and have good breathability but may be not as durable as the next method. The final construction method is a 3 layer construction. This sandwiches the breathable membrane, almost always a laminate layer rather than a coating, between the durable outer layer and a softer inner layer. This construction method is typically found on the higher price point garments which have the best breathability and durability.

So when looking for a new waterproof garment it is important to consider the use that you will put it to, a 2 layer jacket is perfect for gentle hiking, walking the dog etc whereas if you are putting it to use in more demanding terrain and conditions and under more aerobic activity then a more breathable 3 layer jacket may be more suited to your needs or if lightweight is a key consideration then a 2.5 layer jacket may be best for you. Take the time to come in and talk to us about your needs and we can help find the best jacket for you.