Marmot Astrum Jacket – The Fill

Nestled inside the Astrum’s understated, slightly stretchy, olive-green shell is something called Thermal R Active. It’s a synthetic, but more importantly, it’s one a new generation of synthetic fabrics that have been designed to be non-migratory.

‘You can use more air-permeable/breathable materials, which in turn ups the overall breathability of the garment’

In simple terms, that means they don’t try to work their way out through the fibres of the fabric encasing them and that in turn means, you can use more air-permeable/breathable materials, which in turn ups the overall breathability of the garment and means it can be used more on the move without the familiar steamed pudding feel.

The fill also has characteristic damp-tolerant properties. Bear in mind that the ‘active’ bit is all relative. The fibres are quite a passive medium and our overall take is that it’s not as effective solution as Polartec’s pile-based Alpha insulation. Our testing bore that out.

Synthetic Sandwich

The jacket’s certainly more comfortable on the move than an old school traditional synthetic with the fill sandwiched between two layers of completely windproof fabric, but we found it had to be seriously cold for us not to overheat quite fast with any sort of serious pace on.

That’s all going to be relative both to your personal steam rating and the outside temperature and humidity, but we suspect it’s best suite to cold-blooded folk in cold, dry conditions. As ever, your mileage will almost certainly vary.

Marmot Astrum Jacket – Verdict

‘Active’ insulation is a bit of a buzz-word at the moment. As well as the Astrum, we have the single-minded Black Diamond First Light, the VauDe Bormio, the Rab Alpha Direct and Alpkit’s new Katabatic Jacket.

Marmot’s offering is nicely designed, generously cut and works well up to a point. It’s not a jacket we’d recommend if you run hot, but for steady use, by colder-blooded folk in winter conditions and for more static stuff it works reasonably well and has the traditional synthetic water-resistant virtues too.

More Information

See marmot.com