Waterproof Construction (Layers)
Laminates and coatings are relatively delicate, and abrasion can damage the laminate or coating. Thus waterproof fabrics employ some type of skin-facing on the inner and outer of the laminate or coating for protection and are described as 2-layer, 3-layer or even 2.5-layer fabric. Here is brief description of each type of fabric.
There is an assumption that while 3 layer offers the greatest durability, 2 layer is the more breathable. Under laboratory conditions this is certainly the case. In practise however, the lining and the air gap between the lining and the outer fabric on the 2-layer garments inhibits the transfer of moisture vapour. Effectively, the breathability of a 2-layer garment if the same waterproof membrane is used is similar to the breathability of a 3-layer. So, if breathability is comparable why specify on over the other? The deciding factor between 2-layer and 3-layer is durability. For mountain sports where maximum durability is required, 3-layer is recommended.
2-Layer: The Most Affordable
These are comparatively basic garments, where a membrane or coating is applied to the interior of the face fabric (outer protection) creating two layers within the fabric. Often a loose-hanging liner, usually mesh, that is stitched into the interior of the jacket which protects the laminate or coating on the inside of the jacket. This suits many people, though some find hanging linings a little too loose and bulky-feeling. Two-layer jackets are usually a touch heavier than other designs, include more pockets and are primarily intended for day trips or urban activities. 2lyer is typically lighter and softer handle and is ideal for where comfort rather than durability is the requirement.
2.5-Layer: The light weight and packable.
These use a low-weight face fabric (first and outer protective layer), a polyurethane-based WP/BR laminate or coating (second layer membrane ) and a bare-minimum protective inner layer (more like a sheen than an actual layer, which is why it is considered a half-layer). Typically this inner layer is little more than a series of dots, a grid pattern or a spray of resins that provides a touch of slickness and abrasion-resistance. These garments, typically 500grams or less, are intended for ultralight weight travel and spacesaving for travellers. Walkers who favour more breathable soft shells as their principal outerwear often toss a 2.5-layer jacket into their packs just in case a deluge hits and they need full waterproof protection. If abrasion-resistance is not one of your key concerns, 2.5-layer garments deliver high performance for a comparatively modest price.
3-Layer: The Most Durable
Jackets in this category offer rugged yet low-weight WP/BR protection. No coatings in general are used here, primarily laminates, with a membrane tightly sandwiched between the face fabric and a body-facing liner. Designers here seek to shave grams and add refinements as minute as rounded zipper pulls to avoid any angular edges on the finished product. Jackets in the category offer a sleek, athletic fit and face fabrics that can handle less-than-gentle treatment. This makes them well-suited for serious climbers and backpackers. Products in this category aspire to high breathability, high durability and relatively low weight, but can be a more pricy.