• Overall Rating

  : 5 out of 5

For camping in sub-zero temperatures a warm sleeping mat is essential. That means one with an R-value of at least 4, preferably higher. The R-value is the measure of the heat flow through a given thickness of material, so it tells you how well a sleeping mat resists heat loss. Sleeping on snow or frozen ground you can lose a great deal of heat with an inadequate mat. The Alpkit Radiant mat has an R-rating of 7.2, which means it should be warm down to -32°C.

This is lower than the coldest temperature ever recorded in the UK (-27.2°C). This means the Radiant should easily be fine on the coldest UK winter nights. I’ve slept on frozen ground at 1100 metres in the Cairngorms on a night when the temperature fell to -5.5°C and the mat was warm. I expect it will be at colder temperatures.

Of course, a mat needs to be comfortable as well as warm for a good night’s sleep and the Radiant is excellent. It’s rectangular rather than tapered and wider than most mats at 64cm rather than 51cm. This means you can spread out and move around without an elbow or foot slipping off the mat onto the cold ground. Fully inflated the Radiant is thick too, keeping you well off the ground.

Alpkit Radiant in use. Credit: Chris Townsend

The Radiant is made of recycled nylon with a layer of reflective material, “like a thin aluminium coating” says Alpkit, that reflects body heat back towards the sleeper. The mat is also constructed with a series of small chambers that restrict air movement in the mat, which also helps with warmth. The air chambers can be seen as a diamond pattern. I like this design as it also helps keep me on the mat compared with tubular designs, where I find I can roll off more easily. The mat does crackle a little when you move about but I only noticed this when sitting in the tent. It didn’t bother me when sleeping.

The Radiant comes with a 20-litre pump sack. Inflation with this is quick and easy. The pump sack adds 104g to the weight but is big enough for a winter sleeping bag as well as the mat so you don’t need a separate dry bag for the former. The pump sack has taped seams and a buckle closed roll top.

The Alpkit Radiant packs down small. Credit: Alpkit

Rolled into the pump sack the mat measures 38 x 11cm, which is reasonable for a mat this warm. The weight of 644g the Radiant is good given the warmth too. As we’ve come to expect from Alpkit, the Radiant mat is great value for money.

How Chris tested

Chris Townsend used the Radiant on high- and low-level camps in the Scottish Highlands in temperatures ranging from +10 to -5°C. Compare these with other options in our sleeping mat gear guide.