compressibility/ packability of wool

In general:

Packability, warmth, robustness: pick two

The Nanopuffs you mention are warm and packable but being high loft insulation they're sensitive to humidity and compression. Wool is robust in that sense, as it is fleece, but they're not much compressible. Packable wool must be thin and then it's not too warm.

If you need high loft (like the Nanopuff) but favor natural materials you can use down.

The closest thing in wool to a thin synthetic jacket ( that I know of) are cashmere and the merino wool/possumdown combo.
Both need to be taken care of when washing but are somewhat odour resistant so you will not ned to do that often.
I have one of each at around 9 oz for M size. They pack down to a 1 L Nalgene size.
I don't have a synth jacket as light as the Patagonia (my Montane is about 500g and much warmer than the jumpers)
but I suspect that the Patagonia will be measurably warmer than my wool jumpers.
Franco

Not what you wuld think of as an expert, but wool is good. So is down. I pack both.
I never bring synthetics, except for a light fleece pullover.

A good wool sweater for packing is probably not made. Merino wool is not very good. When knitted, it produces a fine woven, thin layer. Great for long johns, not what you want for a warmth layer. Nor, do you want a 3/8" thick layer of sweater made of all guard hairs from a wool batch. Pretty heavy, and not too compressable. Something inbetween is good. I have two that I use. One is from Lands End, the other is from some no-name. Look for a fine cloth with some fuzz. They weigh 8-1/2oz and 10-3/4oz.

OK, you need a base layer. Merino wool is good for that and highly recommended. Long sleeves keeps bugs off. Over that you can add your sweater. Worn alone it works to keep you warm and ventilates well while hiking. And, it sort of does double duty. Stop hiking, and the fuzz will hold your heat in, making you warmer. Hike at 2mph and it ventilates well, not allowing you to overheat (this depends on other conditions…, of course.) It packs up to about the size of small cantelope without compression. If it starts getting cold, slip something tightly woven over it. A light fleece works. Now it will hold heat in all the air pockets pretty well…a good insulation layer.

Overall, a wool sweater is good in every category: warmth, cooling/ventilation, insulation capacity, warmth while wet, compressibility, etc. It is NOT the best in any one, though. You can easily find other stuff that will do better in one category at the expense of another. Overall, it is excellent, because it does everything pretty good. BTW, a wool sweater makes a fair pillow, too.

Down is better at insulating. But it requires a fine woven cloth (down proof) holder. It is much warmer…too warm for hiking, generally. And, if you let it get wet, it is not good at insulating. Excelent for compressibility. I carry a light down sweater for around camp and at night. About 11.5oz. Best insulation per pound carried.

Synthetics should never be compressed. It will put permanent compression into the fibers. But these have excelent wet warmth. Again, it will depend on conditions and how you use it. I never carry a synthetic jacket, relying on my light fleece, instead. It does not compress as well, but blocks wind a bit better. Good weight, but large volume.

I think I'll just bring an old wool sweater. I'll try wearing it for an outer layer exclusively for the next few weeks before my trip, and if I don't get too cold I won't worry about a jacket.

I use the Nano Puff for such purposes and I too wanted to use wool first. I own an Icebreaker 320 hoodie, which is about the same warmth. But . . . it is really quite heavy and, yes, takes up a bit too much space. It's the weight over the packability which is the main problem with wool that is warm enough to act as a real insulating layer.

Have you looked at Icebreaker's RealFleece line? Most of the line uses 260g/m2 weight fabric, which is naturally lofted and supposedly insulates like the 320g/m2 – if you are set on merino, it's a good option to consider, as it should pack down better than the 320 weight.

FYI, Sierra Trading Post has the RealFleece Sierra Hooded Jacket for about $100 shipped when combined with a 35% off coupon. Quoted weight is 20oz (although no size is specified for the weight), so it is still rather heavy compared to synthetics. I have one on order, and can verify actual weight when it arrives (hopefully sometime before the end of the week).

http://www.sierratradingpost.com/icebreaker-real-fleece-sierra-hooded-jacket-merino-wool-for-men~p~4743f/?filterString=s~icebreaker-sierra%2F&colorFamily=01

Edit: Hoody arrived, my men's size small weighs 505.9 grams, or 17.85oz. Somewhat heavy, but it would make a decent midlayer if you expect to be exceptionally active in cool weather. Functionally, it's similar to a softshell – although more comfy/stretchy/breathable but minus the DWR/wind-resistance. Throw on a windshirt and you have a very nice combo for hiking in cool/cold weather. It's a fairly technical fit – there is enough space for heavyweight base layers underneath, although loose long sleeve layers might not work so well in the arms. The jacket also has a soft fleece lining on the inside that feels great against skin. The hood is okay, a bit bulky and non-adjustable, but usable and seems to stay where you set it.

All in all I'm pretty happy given what I paid for it, but I imagine that this piece will get more use around town than in the backcountry. I'm not out hiking in cold temps very often, so for most backpacking trips the only time I foresee getting chilled is when I'm not moving, and for that I have a down pullover that weighs about a third as much and is just as warm. Then again, I wouldn't want to hike while wearing down or synthetic insulation under a pack – it would compress and wouldn't be breathable enough to be comfortable.

Holy cow! That's a great deal on the Icebreaker Real Fleece Sierra jacket! I just ordered one.

(It's a good life motto to never pass up Icebreaker on sale.)

I have quite a few wool shirts and sweaters, and it comes down to the individual qualities of the wool used.

Lambswool as an outer layer will lose heat to wind, but by the same mechanism it breaths and regulates very well for hiking in the cold. I wear wool sweaters as midlayers with a tight weave shirt over top for wind, or a windbreaker/rain jacket. Alpaca is ridiculously warm and seems much heavier but also seems less breathable based on the sweater and socks I have made from it.

I recently did a backpacking trip with a lambswool sweater that has a tightish weave and fit snug. It worked well as my insulation layer over a merino base and under a rain shell. It seems to compress more relative to my older ll bean and eddie bauer lambswool sweaters, and has become my go to mid layer. I think it's made by patagucci and it sort of looks like a military repro.

Wool won't suffer from compression, I'm able to get a sweater pretty small by rolling it up and squishing it in a dry bag with my socks. They also don't need to be washed very often and if they get stinky, you can just hang them up in a breeze and the odor goes away.

In regards to merino base layers, I have worn minus 33 and terramar almost everyday for the last year and sometimes wash and dry them with all my other clothes. They don't seem to suffer from this treatment. They might feel a bit different at first, but quickly regain their softness. Am I ruining my base layers without realizing it? I try to wash them cold and hang dry when I remember.

"FYI, Sierra Trading Post has the RealFleece Sierra Hooded Jacket for about $100 shipped when combined with a 35% off coupon. Quoted weight is 20oz (although no size is specified for the weight), so it is still rather heavy compared to synthetics. I have one on order, and can verify actual weight when it arrives (hopefully sometime before the end of the week).

http://www.sierratradingpost.com/icebreaker-real-fleece-sierra-hooded-jacket-merino-wool-for-men~p~4743f/?filterString=s~icebreaker-sierra%2F&colorFamily=01"

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