Lightweight insulation!

Don't own the Prism2 but the original Prism. Its a very good item, packs small, "just enough" insulation for a typical UK winter situation. With a layer under it will do to about freezing and layer a synth gilet over for below-freezing. That will come close to the temperatures when you can then switch to down.

250g/m2 Merino Base can be as warm as a midlayer.

I'd not bin the down jacket unless you're desperate for cash and/or its a bad jacket. Down lasts a long time if stored uncompressed and packed its got the best insulation/weight/volume story.

I'd agree for UK 90% of the winter days, you'd find the Prism sufficient, but just a caution if that's literaly all you're going to take for winter.

As to "run warm" for many that is actually when they are active and/or recently fed. Many who "run warm" then flip to the opposite when they are tired/inactive/hungry because the furnace has no fuel.

Yesterday was my 5th concurrent active day, I did 6 hours hard exercise and I'd miscalculated my lunch requirements, probably due to not eating enough the day before, and began getting hungry before I got home, and I was getting cold. I could then NOT get warm, it was under a duvet wearing clothes for an hour til my next meal warmed me up, then it was back to usual, the least-dressed person in the house. I'm usually in t-shirt and shorts when others fleeces and trousers, but not when I get tired and hungry.

I'd recommend also getting a synth gilet to pack to layer when required over a Prism, even if its packed 90% of the time. 

Last time I looked into this, I ended up getting a mid-weight fleece and a lightweight down jacket. It isn't ideal for all situations... I'd want a warm synthetic jacket for cold, damp situations to round it off.

Thermalpro fleece is relatively light and relatively packable. Its also a fair chunk cheaper than synthetic insulation, breathes better, dries quicker, survives more abuse, etc. It also fits in nicely with my existing selection of shells, and I'm very much in favour of kit reuse. Didn't really see the point of a 'wear on the move' top like the prism in the face of all that, but there are clearly enough people who think otherwise to keep it on the market

I've had a Prism II and found it a perfectly good piece of insulation, with the exception that it really did not fit me.

Arm length and torso fit was ok, but it was far too short in the body for me.  Now, I'm not that tall (5'10") but I regularly got it riding up and darughty about the waist.

A good alternative IMHO is the Sigma from PHD.  Insulation is probably slightly warmer and the outer is potentially more weather resistant too.  Although the hood is far more simple in its design I have found it perfectly functional when used.  If you can cope with the smock fit it might be for you.

If your budget will stretch to it then consider PHD's Kappa.  This time insulation is a fair step up and so is the waterproof outer.  Hood design, pockets and cuffs are also a big improvement over either the Sigma or Prism.

Hope this helps,

J

Montane of all the makes I find the most commonly fitting. My chest and waist a little smaller than yours and I find all the room I need for a fleece under and no tightness, in a medium. The sleeves a little too short and a wrists a little too tight but not so bad I'd want to move up to a Large.

The Prism2, in my view is not as good as the original because of what JJ pointed out, they made it too short so a cold midrift.

I was hoping to try a few Montane and Rab insulated jackets in during last UK visit but opportunity didn't arise so I'm just bumbling through the comining winter with my old Prism, its quite a good jacket.

I'm in the market for a lightweight synth gilet. I have looked at a few including the Montane prism gilet. I found the body fitted me nice and snug in large being a slim fit I thought but way too short for the size (I'm 6'5" but average to slim). It does seem  to be shorter than say the Rab generator smock and the Haglofs Barrier II vest. I know you are not looking for a vest but since it has a similar fit to the jacket  this needs to be considered.

BTW the haglofs barrier II vest and the jacket seem a good option. Perhaps a slightly warmer jacket than the prism but a possibility. It has a nice atheltic fit IMHO.

Take a look in Rohan for down and synth jackets/vests. It really surprised me after someone suggesed on here that I look at Rohan. They do some nice looking vests and jackets in both synth and down.  Looks to be good stuff too. One synth gilet is amazingly thin. Spark I think. The inner  flame is like the prism vest. The jackets all look good and not badly priced I thought.

Nigel Healy wrote (see)

Don't own the Prism2 but the original Prism. Its a very good item, packs small, "just enough" insulation for a typical UK winter situation.

Mike fae Dundee wrote (see)

Nigel Healy wrote (see)

Don't own the Prism2 but the original Prism. Its a very good item, packs small, "just enough" insulation for a typical UK winter situation.

40g/m2 would do me in summer, but i would freeze sitting around in that in winter. I would want at least 100g in the body. Something like the Rab Generator Alpine jacket.

Thought the context was not a belay?

I'd agree, if SITTING but moving, its about-right at the near above-freezing temperatures. Around freezing I add a 100g gilet so thats 140g core and 40g arms. As the temperatures drop below freezing the 40g arms aren't sufficient and yes then need say 133g core and 100g arms. 

Nigel Healy wrote (see)

Mike fae Dundee wrote (see)

Nigel Healy wrote (see)

Don't own the Prism2 but the original Prism. Its a very good item, packs small, "just enough" insulation for a typical UK winter situation.

40g/m2 would do me in summer, but i would freeze sitting around in that in winter. I would want at least 100g in the body. Something like the Rab Generator Alpine jacket.

Thought the context was not a belay?

I'd agree, if SITTING but moving, its about-right at the near above-freezing temperatures. Around freezing I add a 100g gilet so thats 140g core and 40g arms. As the temperatures drop below freezing the 40g arms aren't sufficient and yes then need say 133g core and 100g arms.