UPF rating/sun-protectiveness of wool garments

I wouldn't really count on any lightweight wool as good sun protection. Obviously it depends on the weight and the weave, but the heavier / tighter garments will likely be too hot under direct sunlight anyway.
I too am interested to know the UPF ratings of wool, but just holding up a microlight merino shirt to the light tells me it's negligible (a lot of light goes straight through the weave).

And unlike nylon you probably will have to replace wool garments periodically if they're your only layer and subject to abrasion. It can get expensive.

Thanks for replying, Bradley (Brad?). I'm quite aware that most lightweight wool garments are expensive, not very protective from the sun, and not likely to be durable under constant pack wear, but was hoping that someone would write about the exceptions (if there are any). I really want to ditch the nylon (except in the raingear)!

My apologies; you did say "I wonder if the latter is as protective from the sun" which implied to me you weren't certain of this and were seeking clarification.

A quick and dirty test for rough UPF-factor is to hold a single layer of the garment up to a light source and compare the amount of light coming through to others. Not very scientific, but it can actually give you a fairly accurate idea, and that way you should be able to tell yourself by looking at garments you like.
I think the problem you will run into is that any "exceptions" will just be tight weave and heavier. Just physics, right?

I have an 'elusive' BLP Hoody. It is almost the perfect garment. I was really surprised that is was acceptable for temperatures up to 85F.

The biggest concern is probably how well it will hold up where the straps of the pack lay on it… and obviously the lighter the pack, the less wear. So far I have been thrilled with it. The material looks and feels like cotton.

I have no scientific data, but my experience is:

I have light skin and burn easily. I've had dozens of skin cancers removed. I now avoid sun as much as possible.

I wear LS micro-lite wool up to about 85F. After that, wool seems to heat up on my skin in low humidity. Then I switch to poly. So I have lots of both kinds of base layers.

When I hold a 30 SPF Patigonia and a microlite Smartwool up to the light it seems that more light comes through the wool. However, LOTS of light still comes through the poly. I never got a sun burn while wearing either garmet. I hate the stink factor of poly and would wear wool all the time if it was more comfortable above 85F.

I experimented with the REI silk LS underwear. MUCH better odor control than poly, but I did get a sun burn through it.

No doubt, the poly wears better; much better. However, it's not like the wool is super delicate. And I don't experience pack wear on the wool. My shoulder straps keep the pack close to my back. I don't have downward pressure from my straps to my shoulders; hence, no wear spots.

Went to town today so I asked the buyer of one of the largest outdoor shops about this. They sell a lot of Icebreaker ( not only to me…)
IceBreaker do have training sessions however she has never heard them mentioning any specific SPF or UPF rating.
Her opinion is that the new light colored ones would not be that good as they are almost see through , however the black ones including 140 and 150 should be OK for most.
So possibly the lack of specific figures is due to the many colours now available.
I have walked in full sun at 30-40c (86-104f) for many hours with the 140 as well as the 190/200 (I often can't tell the difference) and never burned. I don't easily burn but I can see a distinct difference between the areas covered and the ones exposed when I take the top off. (all black)
IceBreaker suggests the L/S 140 for hot weather.
Franco
http://www.icebreaker.com/site/icebreaker_man_superfine140_ls_inca.html

Thanks for commenting, guys (and for your Icebreaker inquiries, Franco). I'm going to consider your recommendations.