Author Topic: What's the best warm jacket synthetic fill?  (Read 386 times)


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What's the best warm jacket synthetic fill?
« on: 21:10:08, 05/01/21 »
A simplistic heading I know but I would like to buy a new full-zip synthetic jacket, hopefully for spring and autumn use in particular but the choice of the filling appears to be a bit bewildering?

I've come up with a list, Primaloft, Gold and Silver, Thermoplume, Thinsulate, Plumafill, Thermoball and Coreloft. Are they all the same, are they more than just tradenames, are they different from each other? If so which filling would I judge as 'the best' and/or 'the worst?'

I think I know roughly what I'm looking for, a jacket that will keep me warm, if I want to be warmer I'll wear a wind jacket over the top, and I don't want it to hang onto my sweat for too long, so which is the fill I should go for? Any ideas or suggestions, please.


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Re: What's the best warm jacket synthetic fill?
« Reply #1 on: 21:58:07, 05/01/21 »
You could look at the Patagonia Nano Air Jacket. Multi function but the blurb seems to suggest you might not need a wind proof. Iím looking at it for me but lockdown is now in the way. Cotswold have limited sizes around £160 I think


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Re: What's the best warm jacket synthetic fill?
« Reply #2 on: 10:46:25, 06/01/21 »
Ah yes, it's lockdown again so it's time for boring people to death with esoteric gear knowledge!  The silver lining of it all ...

You're asking two questions here, but fundamentally 'the best' depends on the metric you use to judge, is it:

- The most cost effective
- The warmest per weight
- The ease of bringing it with you

In general terms I look at how 'cost effective' something is as how much use I can get out of it before it breaks, or is no longer working as it is intended.  When it comes to down vs synthetic the dichotomies are well known: down is vulnerable to losing all its insulating capability when wet but is expensive, versus synthetics which resist this (yet still reduce performance because of fluid convection).

Why choose a synthetic product

Down is better at keeping you warm, but how much better?  It costs a lot more, so it should be a lot better, right?  From studies on Clo value (insulation metric) we have the following:

500-fill down - 0.7
650 down - 1.0
800+ down - 1.68
Climashield APEX - 0.82
Coreloft (Arc'teryx) - 0.88
Exceloft - 0.68
Marmot Thermal R Eco - 0.8
Polarguard - 0.488
Primaloft Eco - 0.68
Primaloft Infinity - 0.57
Primaloft One - 0.92
Primaloft Sport - 0.79
Primaloft Synergy - 0.73
Primaloft Black - 0.65
Primaloft Silver - 0.79
Primaloft Gold - 0.92
Thinsulate CDS 100 - 0.419
Thinsulate CDS 150 - 0.413
Thinsulate CDS 200 - 0.403
Thinsulate CDS 40 - 0.538

In terms of those choices I tend to find myself using either Primaloft Gold (short fibers, packable, lightweight) or Climashield APEX (long fibers, performs as advertised for much longer).

Ways down loses performance:

- Physically lose down from the jacket through seams or tears.  Solution: buy a quality jacket with good stitching or get it 're stuffed/topped up'
- Down holds dirt/oil from use.  Solution: dry clean it
- Won't reloft properly due to being stored compressed.  Solution: store your down gear loose and uncompressed

Ways synthetics lose performance:

- Compression from being packed away, or wearing it with a backpack/sat in it whilst you're driving all compresses the fabrics.  After this is repeatedly done they do not 'spring back' as they did before. Solution: don't store synthetics compressed
- Damage to the short fabrics.  Most of these synthetics are known as 'short fiber fabrics' because they're packable, move easily and this makes them very useful for putting in a rucksack in a compression bag.  That said, some studies on this have shown short fiber fabrics to lose slightly less than 50% of their performance within six months of casual use.  By comparison, continuous fiber fabrics only seem to hit the same point after 2-3 years.  In terms of cost effective performance this would change the discussion. The short answer to why is because once the fibers are damaged from compression/use then they don't loft up properly, and that lofting is what captures the warm air to keep you insulated.

Performance fleece as an answer

Fleece has been around for years, it's old tech, right?
Well yes it is but it's tried and tested for a reason - firstly I'm going to ignore the issue with microplastics because it warrants its own post.  That said performance fleeces are still being developed and we have some solid insulation from them - especially good if you're doing a longer backpacking trip or wearing a heavy pack and want something which will last for longer. 

Some of the common fleece types and their insulation:

Polartec Alpha 60g/m2 - 0.280 clo
Polartec Thermal Pro High Loft - 0.210
Polartec 100/200/300 - 0.143

Obviously most continuous/short fiber loft based insulator fabrics (when new) are far better than fleece but the important thing is that fleece is designed for active insulation not static.  So you wear it under your backpack straps, it's fairly resistant to light brush and snagging, and it's quite cheap to replace.   

How much warmth do I need?

The short answer is it depends on you.  Everyone has a different metabolism and physiology, some of us run very hot, others are cold all the time.  We'll put on/take off layers based on the weather, how hard we're working and our general pace we like to move at.  A general rule of thumb with regards to clo value is that your 'active' insulation requirement can be tracked by knowing your MET for your activity (Metabolic Equivalent Task), which in the case of backpacking/hiking is usually 6-8 depending on how brisk you walk.  Your 'at rest' warmth requirement (such as at a campsite) should be 4.5x your active clo requirement (as measured by what you actually like to wear when you're comfortable walking when you fall into a sustained pace), assuming environmental factors are the same for both.  Of course this is assuming you've eaten/hydrated properly which when backpacking has a habit of making you feel chilled in the evenings.

So what's the best again?

Depends on your situation.  Whether you wear it all day, whether you intend to backpack with it, if it's going to be replaced/sold, etc.   From a personal point of view I'm between Polartec Alpha Direct / Polartec Thermal Pro / Primaloft Gold / Climashield APEX right now and what is what I have most experience of, but there are some other good options out there.

« Last Edit: 10:49:35, 06/01/21 by forgotmyoldpassword »


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Re: What's the best warm jacket synthetic fill?
« Reply #3 on: 11:37:26, 06/01/21 »
Surely there is nothing more anyone could add ------------------

or can they ;D
So many paths yet to walk, so little time left


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Re: What's the best warm jacket synthetic fill?
« Reply #4 on: 13:43:18, 06/01/21 »
Thank you 'forgotmyoldpassword' that helps me a lot,. I need to re-read it but I get what you are saying. I'm sure it will help me to make a final decision. Once I make a decision I only have one worry, the jacket lining. I've already experienced two similar jackets from Alpkit, same filling, £10 difference in price but one lining worked very well but the other one, my sweat just clung to it. I threw that one away in the end.

Interestingly I looked up Alpkit again, they appear to have 2 or 3 similar jackets of the type I believe I am looking for. They are differently priced of course, but I don't want to buy clammy lining again so if I buy from them again my choice will be a gamble. I have no way of knowing in advance if either of them has a non clammy and decent lining?


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Re: What's the best warm jacket synthetic fill?
« Reply #5 on: 14:28:31, 06/01/21 »
Surely there is nothing more anyone could add ------------------

or can they ;D
Is that a challenge?  ;)

I would add that in the last few years, there's been a trend towards "blow in"/"downlike" synthetics. These are ones where the synthetic material is made to act like down and is blown into baffles as you would with down, rather than being a sheet of insulation. Examples include Primaloft Thermoplume, 3M Featherless and Rab Cirrus HL. I haven't tried any of these yet, keep considering them, but not sure about their durability compared to sheets of insulation.

For insulation on the move, I like Polartec Alpha. I've got the Rab Alpha Flux, which is made from Polartec Alpha Direct ie it doesn't have a backing, you've just got the fluffy insulation on the inside. Sheds sweat brilliantly, you don't have to keep taking it on or off as your exertion levels change. I suppose it's really just fancy fleece but I like it. I wore it on a cold, snowy day up Fan Frynych over a Rab thermal base layer and didn't need any other layers while moving, but have also worn it over lighter base layers when it's just a little chilly in spring or summer.

For stops I have a Primaloft Silver-filled jacket from Berg that I got cheaply from Sports Direct about 4 years ago. Unfortunately I made the mistake of wearing it as a general every day jacket, travelling in the car with it on and so on, and it seems rather thin in places now. For local walks (ie all of them at the moment) I've taken to wearing a Rab Original Pile fleece jacket. Wouldn't want to lug it up a mountain and it can get a bit warm but it's very rugged, so seems a better bet than some delicate lightweight insulation when there's no need to go light.

Hope that helps rather than confuses further.


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Re: What's the best warm jacket synthetic fill?
« Reply #6 on: 14:38:32, 06/01/21 »
Surely there is nothing more anyone could add ------------------

or can they ;D

You can tell it has been a quiet week.. :D


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Re: What's the best warm jacket synthetic fill?
« Reply #7 on: 15:10:22, 06/01/21 »
Well, there's nothing can beat a good hand knit woollen sweater under a waterproof layer in the height of winter, in my personal opinion.

They are the ultimate in warmth giving properties, crush proof, air trapping, smell capture, the lot. When you need to carry them then they tie around your rucksack waist belt a treat and can keep your backside cosy. The right wool is also quite resistant to drizzly rain, and unlike down dries out smashingly fir immediate reuse if soaked through, like when I tumble into the mire. OK Mrs. Jimbob gives me that look when I sneak it into the wash after such events, but as I gently explain to her, she knit it for me and given my past history she must have accepted it was always likely to get dirty.

In summer I use a light fleece now following similar topics on this forum.
Too little, too late, too bad......


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Re: What's the best warm jacket synthetic fill?
« Reply #8 on: 06:28:11, 07/01/21 »
Maybe too warm for your purposes, but I've just bought a Snugpak Torrent, an insulated waterproof, and am amazed at how warm it is. I just had a merino base layer under it, and was toasty warm at - 5 degrees C.

I got it for less than half price on the Internet, and it seems to be a great purchase.