How To Choose A Synthetic Jacket

We stock a massive range of synthetic insulated jacket. From breathable wear all day layers to big, burley Scottish Winter belay jackets we've got it all, but which one is right for you?

Starting with our Facewest Warmth Rating: choose the rating that matches how cold it'll be and how much you'll be moving, then pick the insulation type and shell that suit British weather. Every jacket in our synthetic insulated range carries a rating from 1 to 4, and you can filter the collection by it.

Synthetic insulation keeps working when it's damp, dries fast and breathes better than down, which makes it the natural choice for wet, windy UK hills and for warm layers you wear while moving. We will explain what each rating means, which activities it suits, and which jackets sit where.

Scottish Winter, the ultimate jacket test.

 

The Facewest Warmth Rating

The Warmth Rating is a 1–5 scale for how warm a jacket is overall, so you can compare across brands and insulation types. That matters with synthetics: brands quote insulation in grams per square metre (g/m²), but 60g of one fibre isn't as warm as 60g of another, and a windproof shell or fleece panels change the picture again. The rating gives you one number to compare.

Rating	Facewest label	What it means in practice
1	Midlayers & 2 Season use	Light, breathable "active insulation" to wear while moving, alone or under a shell.
2	3 Season Belay & Hiking	A warm outer layer for cool days, summer alpine belays and stops on hill walks.
3	Winter Hiking & Everyday	Proper UK winter warmth for walking, travel and daily wear, often with a weather-resistant shell.
4	Winter Alpine & Mountaineering	A belay jacket for Scottish winter and alpine climbing: high warmth, helmet-compatible hood, tough shell.
5	Polar & High Altitude	Expedition warmth. There are no rating 5 synthetic jackets in the current range, so look at down for this.

Many synthetic jackets span two ratings (1–2, 2–3, 3–4). Breathable designs work as a midlayer when you're moving and as an outer layer when you stop, so they genuinely cover both uses.

Two rules of thumb when choosing a rating:

• The less you move, the higher you go. Standing on a belay needs far more insulation than walking uphill at the same temperature.
• Layering counts. A rating 1–2 active layer under a waterproof, plus a rating 3–4 jacket in your pack for stops, is the classic UK winter system.

Patagonia NanoAir, the kind of breathable warmth where synthetic excels. 

 

Which rating for what you do

For moving in cool weather, pick a rating 1–2 active layer; for UK winter walking and everyday wear, a 3; for winter climbing and belays, a 4.

What you'll do	Rating	Type of jacket to look for
Running, fast hiking, ski touring, climbing on the move	1	Breathable active insulation, stretch panels, often a vest or light hoody
Spring to autumn hill walking, summer alpine, cragging stops	1–2	Versatile hoody that works under a shell and on its own
3-season belays, cold camps, cool-weather travel	2	Packable puffy with a light windproof shell
UK winter walking, dog walks, commuting, everyday cold and damp	3	Midweight jacket with a weather-resistant shell, or a pile shirt worn next to skin
Scottish winter, alpine climbing, long belays in wet snow	4	Belay jacket: high warmth, weatherproof shell, helmet-compatible hood, two-way zip

Active insulation (ratings 1–2)

This is where synthetic beats down outright. Air-permeable insulations (Polartec Alpha, FullRange, PrimaLoft Active, Octa) let heat and sweat escape while you work, so you can leave the jacket on all day instead of stopping to swap layers. Expect less wind protection than a puffy; wear a shell over it in poor weather.

Puffy jackets (ratings 2–3)

Classic quilted jackets with a light, windproof shell. They're the synthetic equivalent of a down jacket: pack small, go on at stops, and cope with drizzle and damp far better than down.

Pile systems (ratings 2–3)

Pile-lined shirts and jackets (like Buffalo) are worn next to the skin with no base layer. The windproof outer and pile lining move sweat outward, so they stay warm in wet, cold weather. They're heavier and bulkier, but a favourite for Scottish winter and wet-weather work.

Belay jackets (rating 4)

The warmest synthetics in the range, built to go on over all your layers when you stop in wet snow. They're the right choice over down when conditions are damp, because they keep insulating if the outside gets wet.

Other things to weigh up

Once you know your rating, these details decide which jacket in that band suits you.

• Insulation type. Continuous sheet insulations (PrimaLoft Gold, Coreloft) are durable and reliable when wet. Loose-fill or down-like insulations (PlumaFill, Aetherm, Polarloft, ThermoPlume) pack smaller and feel more like down. Air-permeable active insulations (Polartec Alpha, FullRange, Octa, PrimaLoft Active) breathe best for high-output days.
• Insulation weight. Quoted in g/m² (for example 40g, 60g, 100g). Within one brand and fabric, more grams means more warmth; across brands, trust the Warmth Rating instead.
• Breathability vs wind protection. The more air-permeable a jacket, the better it vents sweat, and the more wind it lets through. For windy, exposed days, pair an active layer with a shell or choose a jacket with a windproof face fabric.
• Shell fabric. Light Pertex Quantum shells save weight; tougher fabrics like Pertex Quantum Pro and Drilite Loft add weather resistance for belays; a waterproof shell (like Pertex Shield) lets the jacket double as outerwear in rain.
• Hood or no hood. Belay jackets need a helmet-compatible hood. For an active midlayer, a close-fitting hood that fits under a shell hood, or no hood at all, works best.
• Jacket, hoody or vest. Vests keep your core warm without overheating your arms and layer neatly under a shell.
• Fit. Active layers fit close to wear under a shell; belay jackets are cut roomy to go over everything.
• Synthetic or down? Choose synthetic for damp conditions, high-output activity, easy care and lower cost. Choose down for the best warmth-to-weight in cold, dry conditions, and for rating 5 expedition warmth.

Quick checklist

1. Pick your rating from how cold it'll be and how much you'll move.
2. Decide active layer or stop layer: breathable insulation for moving, a puffy or belay jacket for standing still.
3. Choose the style: vest, jacket or hoody; belay cut if it goes over your shell.
4. Check the shell for wind and weather protection.
5. Get the fit right for the layers you'll wear with it.

Still unsure? A jacket that spans two ratings (like 1–2 or 2–3) gives the most flexibility across the year.

Looking after your synthetic jacket

• Wash with a technical wash (not standard detergent or fabric softener), following the care label.
• Tumble dry low if the label allows; synthetics dry much faster than down.
• Store uncompressed to keep the insulation lofty.
• Reproof the shell with a DWR treatment when water stops beading.