Marmot Isotherm Hoody – Climbing Gear Review


Marmot Isotherm

CGR tests the Marmot Isotherm using the new Polartec® Alpha filling.

In outerwear’s natural selection, our award-winning Isotherm Hoody is evolution at its best.


Style ****


Marmot have been busy, earlier in the year we tested the Nabu Jacket using the new Polartec Neoshell® fabric, this time they have devised a breathable insulation jacket using the new Polartec Alpha® fabric.

So, let’s look at the filling: Polartec devised an insulated filling for the US Special Forces which could insulate yet be breathable in cold, active conditions. It provides all the benefits of a traditional synthetic insulation piece, compressible, light and warm when wet and yet is breathable.

The filling works because the fibres are vertical and not horizontally positioned like a traditional insulation jacket. So imagine a waffle like netting with the insulating fibres pushed through the small squares to look like a brush. The fibres then act in a direct wicking action to deliver sweat through to the outer fabric.

The Marmot Isotherm Hoody is a wear all day jacket, you can wear it on the approach and then climb it. You will need another shell for rain, snow or very windy days but it did perform well in all the climbing situations I put it through. In fact it has become my jacket of choice for all mountaineering activities. I often have to put a jacket on and leave it on, when I’m out training for my MIA I’m in a jacket all day so having a jacket that could breathe was really helpful.

Of course, it didn’t keep me dry when sweating. Many people think that modern breathable fabrics act like a string vest and will keep you  dry even when you are charging up the side of a mountain. But that’s not the object because we know that it doesn’t work that way. What we want is for the garment to dry out quickly when we arrive at the route or stop for a while. The Marmot Isotherm Hoody was designed for just that. The inside of the jacket was perforated in all the main sweat areas, the back and under the arms. This allowed the moisture to be wicked away very efficiently.

The perforated lining helped shed moisture on those sweating approaches.
The perforated lining helped shed moisture on those sweating approaches.

The outer fabric is made from Pertex Quantum, a very light fabric with a micro ripstop weave. It was stretchy on the shoulder area to help in climbing situations. The fabric seemed robust enough and I’ve been climbing in it solidly throughout the autumn and it isn’t showing any signs of piling or have any bobbles. The Pertex Quantum was also inside where it wasn’t perforated.

It was reasonable at shedding a shower or light snow but soon began to get wet. You would need to definitely wear a hardshell over the top. I wore it with both a lightweight hardshell and the Marmot Nabu softshell jacket over the top and was fine. It didn’t feel too bulky under a shell and compressed nicely whilst still keeping it’s insulating properties.

The fit was standard belay jacket. It was fine to wear over a midlayer top when on a belay or on a colder day when hiking. It would also be great for skiing or any active wintersport, although it isn’t a full winter parka. It was great for those chilly rock climbing belays when you need an extra layer. It would have been nice to have an integral stow pocket so that it could have been clipped to a harness so you need to have it stowed in a pack, this did affect it’s portability. I must say though that it is very light and it stuffed into any small space in my pack.

The cut was great for climbing in
The cut was great for climbing in and warm on cold climbing days.

The sleeves worked well and the cut meant there was minimal rise when reaching for those high hand holds. The hem was elasticated with piping which gripped around gloves. There were three pockets, two hand warmer pockets that were accessible when wearing a harness and a neat chest pocket that was big enough for a phone, ipod, some energy bars or even a ski pass. The YKK zips all worked well and zip tags worked well enough although they could have been more glove friendly.

One of the real advantages of synthetic insulation garments is their ease of washing. No special treatment or pure soaps needed just pop it into the machine with everything else. No need to add fabric conditioner and a leave it to either dry naturally (with a good shake when dry) or my preference is to pop it in a tumble dryer for 30 mins when it’s almost dry and this really brings back the loft. The Marmot Isotherm washed and dried really well, the loft was good in both situations; this was also true when dried in a drying room.

The hood was adequate for over helmet belays.
The hood was adequate for over helmet belays.

The hood worked well, it adjusted with a toggle situated at the back. I really liked it when wearing a peaked cap and I never felt cold when it was cinched up. It fitted under a helmet very well and the front of the hood did not interfere with vision. It just about fitted over a helmet for belaying but it didn’t fit well enough for climbing.

All in all the Marmot Isotherm Hoody has been a great all mountain jacket, just as good as a lightweight belay jacket as a full climbing midlayer. Warm on those breezy days and it drys out as quick as a flash.

Marmot offer a full range of sizes from Small to Extra Large and four colours to choose from. There is also a women’s specific version in sizes from XS to XL and more details of that jacket can me found here.

SRP £180.00


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