Chris Townsend reviews this compact and ultralight mid layer option from Berghaus

This is an astonishing jacket. It’s the equal lightest garment tested yet also the warmest. It packs down into a much tinier bundle than any of the others too yet still has a hood, pockets and full-length zip. The HyperTherm Hoody really deserves the description ultralight. Berghaus has achieved this by sandwiching a thin layer of its Hydroloft insulation between two very thin layers of nylon. The tangle of polyester that makes up Hydroloft is far lighter and more compressible than the thinnest fleece or wool.

It’s also non-absorbent so although the HyperTherm isn’t waterproof it dries very quickly and keeps most of its warmth when wet. The shell fabrics are different on each side with one being more windproof than the other and the jacket is reversible, the idea being that wearing the less windproof side on the outside makes it cooler by allowing more warmth to escape. I can’t say I’ve actually noticed much difference though.

The HyperTherm is soft and comfortable. However the material doesn’t stretch and I needed a size larger than usual to allow free movement. The smooth fabrics don’t bind with other fabrics and the jacket works well under a waterproof shell.

The hood is close-fitting too and doesn’t feel bulky under a waterproof jacket hood. It’s not adjustable but fits snugly enough that the wind doesn’t blow it off. The pockets are on the more windproof side and are just usable when wearing a pack hipbelt though the bottoms are cut off. If weight and bulk are important this is a superb jacket.

Breathability is good, as is wind resistance, and I’ve found it works well both as a mid layer and, in dry cold conditions, as an outer layer. I find it too warm to wear while walking in summer but the low bulk and weight means it’s no hardship to carry it for rest stops and chilly camps. The fabrics are thin and it probably wouldn’t stand up to much rough usage – I wouldn’t use it for scrambling – but for hillwalking and backpacking it’s ideal.

Reviewed in November 2015 issue