When it comes to outright warmth for weight, ducks and geese are the undisputed insulation champs, thanks to the fluffy down plumage hidden beneath their feathers. That’s why down is used for the warmest and priciest insulated jackets. Sheep have also got it covered for daily life on claggy hills and mountains – particularly the antipodean super-sheep that is the merino. Hence why superfine merino wool is the yarn of choice for performance base layers.
But one man-made fabric still reigns supreme when it comes to mid-layers, and that is polar fleece. First developed in the late 1970s, this new synthetic wonder fabric was lighter and softer than wool. It was also much cheaper and more versatile than down. If it got wet, fleece was quicker drying than a heavy woolly pully or a soggy down jacket. Made from polyester pile, it was warm and comfortable. Ok, it wasn’t particularly windproof but on the flip side, it was very breathable.
Fleece proved to be a big hit, and soon every brand started making fleece jackets, making the leap from technical outerwear to an everyday wardrobe staple. Today, they come in multiple variations, from lightweight, breathable gridded microfleece tops to uber-cosy, high-loft fleece hoodies. Everyone’s got one, from Alex Honnold to your granny.
Fleece and the environment
Of course, in these more enlightened times, we’ve now realised that a fabric made from petrochemicals is not so great for the planet. Similarly, disturbing research has shown that these fluffy synthetic fibres also release tiny strands and particles called microplastics into the environment, mostly when they are chucked into your washing machine. The outdoor industry is trying to find solutions to these problems and many fleeces are now made from recycled polyester, which is something but more needs to be done.
However, innovation continues to amaze. In 2021, multi-national New Zealand outdoor gear brand Kathmandu launched a world-first range of fleeces made from Primaloft Bio. This fully recycled fabric looks and performs the same as traditional fleece, but it breaks down at an accelerated rate in oceans, wastewater, and landfills - the three places fleece fibres usually end up.
Key features to look for in a fleece jacket
Weight: There are three weights of fleece: 100g/m², 200g/m², and 300g/m². Naturally, it depends on what activity you'll be doing in regards to suitability.
100g/m² fleece is the most breathable and the lightest - it's ideal for fast hiking, climbing, and other high-output activities.
200g/m² fleece is a great mid-layer on a hike underneath a hardshell waterproof layer. It strikes a good balance between warmth and breathability.
300g/m² is best for very cold winter hikes. In most cases, 200g/m² is fine for cooler UK conditions unless you're embarking on an expedition that plunges well into the negatives. This weight is also quite common in everyday-use, relaxed-fit fleeces.
Breathability: The design of the fleece matters here. A common method used to achieve this is to use a grid pattern on the inside of the fleece. It looks like a chequered pattern, with the thin channels in between the squares allowing for perspiration to evaporate easily.
Fit: Slim-cut fleeces with extra stretch are the best shape for wearing while being active because they allow for the best movement and breathability. They are lighter fleeces and can be worn over a base layer and beneath an outer layer. Heavier fleeces tend to have a more relaxed fit in order to accommodate layers underneath them comfortably.
Hood: This simple addition is a great way to gain a lot of extra warmth in a fleece without sacrificing breathability. Some may find a tucked away hood annoying and that's fair enough.
Zips: Quarter, half, or full-length? Quarter-length zips are lighter and are warmer but the hardest to take off; full-length zips are the easiest to remove but are heavier and compromise warmth due to a longer seam and half-length is a good in-between.
Pockets: Hand pockets on the sides are very useful, just make sure that if you are going to use a harness, the pockets are well above the hip line so you still use them. You might want to consider a chest pocket too, for some extra and secure storage space.
Thumb loops: These aren't a necessity at all but they are useful at keeping sleeves down.
The best fleece jackets for hiking
Black Diamond Factor Hoody
Verdict: Great for tough winter adventures, this fleece finds an optimum balance between warmth and breathability. But it would benefit from significant sustainability improvements.
Features 4/5 | Fit 5/5 | Comfort 5/5 | In use 4/5 | Value 4/5 Sustainability 2/5
Overall score: 80%
Pros: Great fit and comfort , nice warmth-breathability balance, suitable for most seasons
Cons: Poor sustainability, no thumb loops
Like a lot of US brands, Black Diamond kit is sized generously, so you may want to drop down a size. Once we’d done that this proved a great-fitting layer, with a trim silhouette but plenty of length in the arms and body.
The fabric has good in-built stretch for first-rate freedom of movement, making this an ideal hoody for scrambling and mountaineering. The fabric is a smooth jersey knit, which means it slides easily underneath a shell or a windproof and doesn’t ruck up when you’re trying to pull on your waterproof just before the heavens open.
The soft microfleece inner offers good comfort levels, with vertical channels to aid breathability. This strikes a great balance since the heavier fabric offers increased warmth over lightweight gridded microfleece, without sacrificing too much breathability. That makes this a fleece you can wear all day as a winter mid-layer, using the full zip for venting if needed – as well as the chest and twin hand pockets since these are all mesh-backed to aid cooling. Pockets are placed high enough to avoid a rucksack hipbelt, and you also get a good hood. It doesn’t hug the face quite as closely as some, but there is a generous chin guard at the top of the zip to minimise irritation.
The sleeves lack thumb loops, but they are at least long enough and tight enough to cover the wrists. There’s a small amount of natural wool (2%) in the fabric blend, but no recycled fabrics.
Fabric Stretch 265gsm jersey face fleece (92% polyester, 6% elastane, 2% wool) | Weight 391g | Sizes men's S-XL, women's XS-XL
Alpkit Keeshond Jacket
Verdict: A super-fluffy fleece that delivers in the warmth stakes, so it’s a great value pick for winter hillwalking. But its poor sustainability credentials let the side down.
Features 4/5 | Fit 4/5 | Comfort 4/5 | In use 4/5 | Value 5/5 Sustainability 2/5
Overall score: 77%
Pros: Great warmth for its weight, breathable, anti-odour treatment
Cons: Poor sustainability credentials, baggy hood, short sleeves
Thanks to its high loft construction, this fleece provides very effective warmth for its weight. In conjunction with the trim fit and the ample body length, it makes for a close-fitting, cosy and comfortable layer. There’s also a hem drawcord to help you lock in more warmth, plus a hood, though this is a little baggy.
There are two well-placed hand pockets, a small zipped chest pocket and thumb loops at the cuffs, plus a chunky, smooth-running main zip that is backed with a small baffle to help block draughts. It all makes for a warm winter mid-layer that works well underneath a shell, with low profile cuffs and flatlock seams to add comfort.
It’s also more versatile than you’d think. On test, we didn’t overheat except on one sustained uphill climb, thanks to the use of generous stretch fleece inserts that run up the sides of the body and extend almost all the way down the sleeves. These fleece panels have a smooth outer face and a gridded inner to aid breathability. The high loft’s open weave pile is also good at trapping warm air while letting moisture vapour escape. Lastly, the Keeshond has a Polygiene anti-odour treatment, so it’s a layer that you can wear over and over without needing to wash it too often. That means it shouldn’t lose too much fluff, which both extends the garment’s lifespan and helps to reduce its negative environmental impact.
The hand pockets lack zips and the sleeves are quite short. It’s also very disappointing to see no recycled fabrics used. And it does have the capability to make you look a bit like the Cookie Monster...
Fabric High loft 280gsm fleece (100% polyester) with 210gsm stretch grid fleece panels (97% polyester, 3% spandex) | Weight 502g (men's M) | Sizes men's s-XXL, women’s 8-16
Patagonia R1 Techface
Verdict: This light and breathable fleece isn’t designed to offer maximum warmth but regulates temperature very well, even when working hard.
Features 3/5 | Fit 4/5 | Comfort 5/5 | In use 4/5 | Value 3/5 Sustainability 4/5
Overall score: 77%
Pros: Fantastic breathability, very comfortable, can also be a base layer, good eco credentials
Cons: Not that warm
Patagonia’s Regulator fleeces, the R1 and R2, have become cult favourites among outdoorsy types, particularly stateside. The R1 is the lighter of the two, designed for active use in cool conditions.
The fabric is a blend of recycled polyester and elastane, which gives it plenty of stretch, making it extremely comfortable on the hill. It has a gridded microfleece inner that is designed to deliver modest warmth while maximising breathability. It makes the standard R1 an understandably popular mid-layer for high-intensity mountain pursuits, and some even wear it as a standalone base layer.
However, this Techface version is a little different. Patagonia calls it a ‘crosslayer’, and it can be used as either a mid or a lightweight outer layer in mild to moderate conditions. It has a tougher face finish for better resistance to abrasion, and we found it would even stand up to a bit of classic North Wales drizzle. It also boasts an array of features, including a drawcord adjustable hem, zipped hand pockets and a small inside pocket, as well as a good hood with three-point adjustment and a stiffened peak.
It’s nice and long in both the arms and the body, giving ample coverage, and even though our test sample was a size larger than we’d normally take, the fit still wasn’t baggy. We liked it a lot, not only for its versatile performance but also for its high-quality feel and good eco-credentials.
It’s only really warm enough if you’re staying active – stop for longer than a few minutes and you start to feel chilly (the R2 steps in here). And it’s not cheap either, especially since this is only a lightweight layer.
Fabric Regulator gridded microfleece with Techface outer (69% recycled polyester, 8% elastane) | Weight 326g | Sizes men's XS-XXL, women's XS-XL
Berghaus Pravitale Mountain 2.0 Hooded Fleece
Verdict: If you often wear a fleece as an outer layer, this is a great option for UK hillwalking that is soft, warm, comfortable and a little more protective than most.
Features 5/5 | Fit 3/5 | Comfort 4/5 | In use 4/5 | Value 4/5 Sustainability 2/5
Overall score: 73%
Pros: Very warm and comfortable, looks great
Cons Relatively heavy, no women's sizes, poor sustainability credentials
Berghaus has been kitting out British walkers since 1966, so by now, it knows what we like to wear on the hills. And given many UK hillwalkers’ general mistrust of any jacket that isn’t properly waterproof – like windproofs and soft shells – it also knows that the majority of us will normally be wearing or carrying four layers at most: a base layer, a fleece and a waterproof shell, with maybe an extra warm layer stashed in our packs. And since you only really want to be wearing your waterproof if it’s raining, that means most of us spend a lot of time wandering around the mountains in a fleece.
The problem is that if it’s windy, you get cold. Berghaus’ solution is the Pravitale Mountain 2.0 hoody - a sort of super fleece. It’s made from a comfortable stretch fabric with a soft, warm inner and a tough, tightly woven face that offers better wind protection than most rivals, aided by a full-length fleece baffle behind the main zip. It’ll even shrug off a bit of light drizzle. As such, it’s an excellent all-day jacket for the colder seasons that will work as an outer layer on cool but mostly dry days. Thoughtful design features include a decent hood, stretch-bound cuffs with thumb loops, two sensibly placed hand pockets and an upper arm pocket (perhaps not that useful, but looks cool!).
It’s pretty heavy and bulky, so this is one you want to be wearing, not carrying. The fabric is tougher and more wind resistant than most, but also a little less breathable and not as fast-drying as some. And there’s no women’s version.
Fabric Stretch hard face fleece (93% polyester, 7% elastane) | Weight 480g (L) | Sizes men's XS-XXXL, women's n/a
Rab Syncrino Mid Fleece Hoody
Verdict: Superlight and very breathable, this is a superb active insulation layer for all-day comfort on the move, in cold or mild conditions.
Features 4/5 | Fit 4/5 | Comfort 4/5 | In use 4/5 | Value 3/5 Sustainability 3/5
Overall score: 73%
Pros: Great design, effective use of body mapping, versatile
Cons: Relatively expensive, no recycled fabric
You know those mountain days when it’s warm in the sun but chilly in the shade, and you’re warm enough if you’re moving but get cold if you stop? Those are the days for a jacket like the Syncrino Mid. This hybrid layer isn’t quite a fleece. It uses synthetic and merino fibres, so you can wear it when moving fast and working hard, while also keeping you warm across a range of temperatures. Sounds too good to be true, right? We thought so too, but on test we were impressed.
The jacket uses two fabrics with varying blends of merino and polyester. The main fabric on the torso is a 69-31 polyester-merino, while the lighter panels under the arms use more merino (44%). While both stretchy and comfortable, this second fabric is designed to be even more breathable than the slightly heavier fabric on the torso.
The hood is more comfortable than most, especially when not in use because it doesn't bunch so much. We also like the full-length zip because it makes taking the jacket on and off so much easier.
While the jacket itself doesn't use recycled fabrics, Rab is a Fair Wear Foundation member and a certified climate-neutral company.
Fabric Main fabric, 69% 230gsm polyester and 31% 18.9 micron merino; secondary fabric 56% 160gsm polyester and 44% 17.5 micron merino | Weight 283g (men's M) | Sizes men's S-XXL, women's 8-16
Salewa Tognazza Polarlite
Verdict: This soft and cosy fleece mid layer is ideally suited for winter ridge walks and summits.
Features 3/5 | Fit 4/5 | Comfort 4/5 | In use 3/5 | Value 4/5 Sustainability 1/5
Overall score: 64%
Pros: Excellent in winter, good fit
Cons: Short in the arms and torso, made from virgin polyester, too warm for anything milder than alpine treks
In terms of warmth for weight, high loft is about as thermally efficient as fleece gets. As a result, the Salewa Tognazza delivers a welcome boost of warmth almost as soon as you zip it up. The two-sided Polarlite fabric traps plenty of air, while its furry fibres are also super soft.
It can be a bit too warm when working hard on uphill ascents, but for exposed summit plateaus and long ridges, it is the ideal mid-layer. We used it during Snowdonia’s first snow of the season, and it proved a stellar performer. And while we did find its limits, it was more breathable than expected, thanks to the lighter weight stretch fleece inserts under the arms and down the sides of the body. These also enhance the fit, resulting in a tailored cut that feels close without being restrictive. It has a useful hood too, with a stretch binding for a close fit around the face. Cuffs and hem are also elasticated to lock in warmth. Two angled hand pockets have easy-grab zip pulls, though they are slightly obstructed if wearing a rucksack hipbelt.
A feature that’s lacking is thumb loops, and we’d like a little more length in the arms and body too. But our main complaint is that it is not very eco-friendly. Salewa uses recycled wool in some of its jackets, but this fleece is made from virgin polyester.
Fabric Polarlite two-sided striped 270gsm high-loft fur (100% polyester) with 250gsm stretch inserts (95% polyester, 5% elastane) | Weight 480g (men's L) | Sizes men's S-XXL, women's 6-14