In the past few years lightweight insulation layers have burst onto the market. To be used either as an emergency insulation layer on the hill by runners or weight conscious climbers or as a mid layer/outer layer for runners in very cold settings, they have pushed the limits in terms of the lightest materials, and the amount of insulation they can get away with whilst still calling it insulation.
Different types of insulation in the test
All the insulation layers in this comparative review use synthetic insulation, generally one of the Primaloft family. Once wet through from rain or sweat the jacket manages to retain the same amount of insulation as it would do when dry, making them a good emergency layer for Britain, as we know, when things get cold here, they tend to get wet as well.
A number of the brands have begun to use double-sided jackets, windproof on one side and breathable on the other, with the insulation sandwiched between them. The theory here is that with the breathable layer out, there is some insulation, but the wind is able to blow through the insulative layer and provide a cooling effect as you travel. With the windproof side out, the wind is no longer able to waft away the warm air that is being trapped inside the jacket, and so you stay warmer.
I’m a size Small. All layers on test here are size Small. Every item of upper body clothing I wear for the outdoors is size small, so I am comparing the sizes against that. (my girlfriend is between a size 10 and 12 and has been nicking all the layers to wear as well).
All tests were conducted using a single synthetic base layer (helly hansen lifa, since you ask), and when really gnarly, this was backed up with an eVent running smock which went over the whole lot. This would be my typical clothing system when running in the hills.
About the author
Tim Budd is a Chartered Physiotherapist, Summer Mountain Leader and keen fell runner. He recently won the MRT Challenge race as part of the Montane Spine Race and along the way he gave a few of these jackets a good bashing.
To check out the jackets either scroll down the page or follow the links to your favourite brands below.