2, 2.5 or 3 Layer: Choosing Waterproof Breathable Construction
Over the years, the construction of waterproof-breathable garments has evolved, but the elements that any garment needs are still the same: The first layer is the face fabric, the durable fabric that is the outside layer of protection against the elements (it is also the layer that sports the design and colors that make you look cool). The second layer in is where the magic happens, the waterproof breathable part of the fabric. The final inside layer is the layer that protects the waterproof coating or membrane from abrasion and pore-clogging contaminants and helps the jacket feel good on your skin. The methods of construction are named for how many of these elements are fused together in the final fabric, and there are three main types:
2 Layer Construction
In this type, only the face fabric and the waterproof-breathable layer are laminated together. The inner protective layer is a separate fabric or mesh liner that hangs on the inside of the jacket. This was the original waterproof-breathable construction. The principle benefit is comfort, as that hanging liner forms a nice interface with the skin. The drawbacks are weight (the added layer adds ounces), bulk (the hanging liner makes the garment harder to pack down, and breathability issues (the liner is one more layer moisture needs to get through). This is most commonly seen in casual and fashion jackets, and some rain pants.
2.5 Layer Construction:
This was introduced when Gore-Tex Paclite first hit the market in the mid-90s, and is now the most common type of construction for lightweight rain gear. The face fabric and waterproof-breathable layer stay more or less the same, but the protective fabric or scrim gets eliminated in exchange for a printed or sprayed-on partial protective layer. This is the lightest, most flexible, most packable, and often least expensive construction available. The main drawbacks are durability, because reducing the protective layer increases wear on the waterproof-breathable layer, and breathability, because the spray-on protective layers do not reliably breathe as well as hanging mesh or laminated scrim. 2.5 layer construction is ubiquitous in lightweight and ultralight gear.
3 Layer Construction:
This came along to answer the needs of alpinists and hardcore users who wanted to address the drawbacks of 2 layer construction. A very lightweight scrim fabric is laminated on the back side of the waterproof-breathable layer, effectively making a sandwich between the scrim and face fabric. This made the fabric lighter, more packable, and more durable (because the waterproof-breathable layer was never exposed, even to the inside of a hanging liner). The drawbacks to 3 layer construction are that losing the liner decreases comfort, laminating three layers together decreases the flexibility of all three, and more intensive production drives up the cost. You find 3 layer construction in the top of the line gear from most companies.
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