Outer layer

The outer layer is a waterproof and windproof layer designed to protect you from the effects of rain and wind. Most commonly this is in the form of a hard shell waterproof jacket, often utilising a Gore-Tex membrane or a brand’s proprietary technology. The sole purpose of such a layer is to keep you dry, so it’s important to gain an indication of how waterproof a certain product will be. Do this by checking the hydrostatic head (HH) rating – the technical measurement of waterproofing. If you’re likely to encounter heavy and sustained rain, opt for a jacket with a 20,000mm HH or higher, which means a 20m column of water can stand on the fabric before water penetrates it. For gentler showers, a lighterweight jacket with a lower HH rating will work fine.

The big downfall of waterproof outer layers is that they can feel clammy and sweat-inducing. The solution, in theory, is to choose a jacket with a high breathability rating. Products with a 20,000g/m²/24hr breathability rating or higher – a measure of how quickly moisture

is wicked away from the body and released through the fabric – will offer the best breathability available. But take these figures with a pinch of salt, because it’s annoyingly easy to overheat in a hard shell.

One other option – that diverges from the classic 3-layer system – is to utilise a water-resistant and windproof soft shell jacket or windshirt instead of a hard shell. Such jackets can provide all the protection you need from wind and rain, except in particularly torrential downpours, and may prove lighter, more comfortable and significantly more breathable than a traditional waterproof jacket.

Paramo and Buffalo are brands synonymous with a non-conformist approach to layering. Paramo’s waterproofs – which use ‘directionality’ technology – are warm, windproof, breathable and designed to be used with just a base layer, while Buffalo’s double-p (pile and Pertex) jackets can be worn next to the skin and replace several layers.