Base, Mid and Insulation Layer
Water conducts heat away from your body 25 times faster than air so a quality base layer is vital. The fabric used generally is ‘hydrophillic’ which wicks away moisture from your skin to be picked up by the next layer or taken away by the wind. Of the various fabrics, polyester, polypropylene, polymide or merino wool are used in base layer construction.
Polypropylene is thin and a can really smell after a day on the trail, polyester has a low wicking ability and doesn’t feel good on the skin, merino wool is natural, absorbs 35% of its weight in water before it gets overloaded, it doesn’t smell but depending on the weight and weave can sometimes be too warm. Polymide, although the most expensive, is light, stretches to conform with the skin which helps wicking, doesn’t smell and feels great on. Certain materials also have UV benefits and close reading of the technical details of each garment is important.
Various thickness are available to suit your activities. They can be round necked or have a neck zip. During cooler weather the latter is good for venting. Usually with long or short sleeves some have longer lengths than others, which help the comfort when backpacking, running or cycling. Merino wool base layers are usually about 200 gms/sqm and have the additional feature of keeping you warm when wet.
The middle layer of clothing is designed to keep you warm when on the trail. This layer has to deal with the moisture transferred from the base layer, so it needs to wick that moisture away or absorb it without losing much of its insulation properties.
Traditionally this has been the thicker standard fleece based garments around the 300 weight. However the garments people use these days have changed to a 100 fleece or the 250+ gms/sqm merino wool product. Ultimately the lightweight backpacker, not only carries less, but also moves faster. When doing so we all generate heat, and a lighter mid layer, has been found to be perfect when moving. It is only when stopping a windshirt, or additional insulation layer is required to prevent the chill factor.
Fleece is made from recycled plastic bottles, insulates well, wicks moisture away efficiently, is lightweight, hard wearing, non-absorbent and dries quickly.
Pertex stretch equilibrium shares all of the same properties, but has directional stretch and more wind resistant. Thermaskin also shares wind resistance, is light, stretchy and dries very quickly.
Unlike a mid layer, which you use when active, the insulation layer is more ‘camp wear’ or ‘warm wear’ in low activity times. Time waiting at the crag, watching a clear starry night in Glen Feshie, or hopping on a bus in Cusco, is greatly improved when the wind is kept out and the warmth kept in.
Without question ‘down’ is the most efficient warmth per weight material you can get for insulation purposes, however it has one drawback. Once wet, is loses its fabulous properties and takes a while to dry. However these products all have excellent DWR skins these days and will take a reasonable amount of damp weather before the water penetrates.
Primaloft is the synthetic alternative.
The fill power has improved these days and depending on manufacturer and the quality of the Primaloft used, it is comparable to a quality down or a 300 fleece. When wet it will still have insulation properties. However like down, it does take time to dry, but unlike down you can still use it during this time. It is 10-20% bulkier than down to pack, but has other advantages as generally the insulation is put within more ‘active’ clothing. Whereas ‘down’ is more camp wear or high altitude, Primaloft is generally found in hardwearing outdoor clothing.
Both ‘down’ and Primaloft are warmer than a standard 300 fleece, without the packing bulk. Generally they are used in garments which have a highly wind resistant outer skin too!
Look after any of these products by airing them and storing them ‘un-stuffed’ and they will last you for years.
Part 2 - Windproof smock and jackets, waterproofs, the all-in-one approach, headwear