Please educate me on insulating pants

"The only time I ever had noticeable loss of loft was when I had a GoreTex shelled sleeping bag. I felt secure enough with this shell (I was gullible enough!) to think that it meant I didn't need to keep water off my bag…WRONG. I also think this shell lead to more internal moisture from perspiration, so it was kinda a double whammy."

While GoreTex is excellent at keeping out external moisture, it's also very good at keeping it in, too. The addition of a membrane can only decrease the breathability of the external shell, which means that more water vapor (perspiration) will condense inside the shell than would have with just the regular shell. This can be a real problem at below freezing temperatures, where ice can build up inside the bag over time, increasing weight and decreasing loft. Sleeping in such conditions for more than a few days would benefit from the use of a VBL liner.

Thanks again for everyone's replies and additional throughts on loft/moisture. This is all super helpful!

For me, I'm thinking I'll be going with down as I believe it's going to satisfy my requirements: warmth while stopped (99% of the time in camp) or while sleeping, very light pack weight, compressibility.
Moisture should not be too much of an issue for my expected use, as the pants would only be used below freezing and I'd wear them under my rain shell pants. Something like 6oz. for the Western Mountaineering Flash pants is very appealing too.
These pants are a very situation-specific piece of gear, and I don't see using them all that much. However, I typically find myself spending the most time thinking about the items I will rarely use!
Again, everyone's input is most helpful. I love this site!

If you can get pants with side snaps, they are very easy
to put on and off, even over crampons and can be vented easily.

Over-insulating the legs can help keep feet warm.

I have some self made thinsulate and PTFE pants that
weigh a whopping 16 oz. (heavy by ultralight standards)
but even in subzero standing around often let me go
without a thick parka. They also keep out the wind
very well and allow a sitting belay in snow without getting
wet through.

http://i.word.com/idictionary/COLLAPSE
The lexical definition of “collapse” is:
1 : to fall or shrink together abruptly and COMPLETELY : fall into a jumbled or flattened mass through the force of external pressure
2 : to break down COMPLETELY : disintegrate

In summary, immersion will collapse down but 100% humidity for month long periods will not.

If your down bag or quilt was unoccupied, the worst case scenario from 100% humidity is ~60% reduction in the insulation value from moisture versus ~40% for Polarguard Delta (Polarguard research). A bag or quilt appropriately rated for the temps combined with your body heat will result in a much lower worst case warmth reduction in 100% humidity environments.

Richard-

I too have spent a rainy several weeks in the North Cascades
on OB courses and one time a used a 25 year old cotton shelled down bag from LL Bean. Slept under a tarp.

No problems, no collapse.

It did stay in a plastic bag during the day, so it would not
absorb moisture from the sodden backpack.

I traded out for a cheap synthetic bag the next trip and it worked
fine too, tho my rough heels shredded the lining beyond
use in 3 weeks. The tighter woven cotton held up better
than the loose woven nylon.

Just shows that there many variables and trade offs.

I currently carry a pair of military poly insulated pant
liners in my SAR pack. Adds extra insulation for little
weight (about 10 ounces) and slides on easily so a cold
rescue victim can be covered quickly. The best part is
they cost 75 cents at a yard sale. If the victim rides
away in a chopper never to be seen again, oh well.

I have pretty much done the same thing as Brian. I bought the BPL Cocoon Pants, and have barely used them. Some of that may be because my legs don't get that cold. I find that rain pants (which I always carry) are usually enough, and if not, a thin pair of long johns is enough. I typically hike in the Northwest summer (when the days are long) so I'm usually in bed before it is cold and usually hit the trails fairly quickly in the morning. If I did more fall camping, then maybe I would use the puffy pants more.

Now, the Cocoon Pullover is a completely different matter. Not only is it a nice piece of gear for summer backpacking, but it works really well in winter. I have considered the Cocoon Pants for the winter, but I like the flexibility of my full zip fleece (since I'm often on skis).

"While GoreTex is excellent at keeping out external moisture, it's also very good at keeping it in, too."

My experience is that Goretex keeps water out OK as long as a) The water doesn't enter through the seams, and b) there is a good temp gradient working. GoreTex can't distinguish between inside and outside without this temp gradient, so if you pack a GoreTex bag with water on the outside and the outside of the packed bag become warmer than the inside, the water will move in the other direction (into the bag). This seems to be the usual pattern of movement, as the bag is packed in the cold hours of the morning and the temp usually rises throughout the day, resulting in the outside of the bag becoming warmer than the inside.

Aside from that, developing the good habit of immediately rolling or stuffing your down garments/bags as soon as you remove them helps rid the down of any warm moist air that is trapped inside. Of course, if the warm air has condensed on the inside of the bag, this won't be as much help. I have not (yet) found this to be a problem with down garments, only bags…

My experience is mainly in Aotearoa, which is the indigenous word for "land of the long white cloud". Rain and high humidity are the norm rather than the exception.

I use homemade synthetic pants (polarguard 3D) for ski trips in the Sierra Nevada. I chose the synthetic over down mostly becuase I was not going to make my own down gear – too much hassle with the down from what I have heard and my experiences in the past. Plus, when you get down to that end of the spectrum (my pants weigh 9 oz) there is very little difference in warmth/weight ratio, due to the fact that the down needs quilting lines and the polarguard does not, so that the consistency of the thickness of the synthetic just about cancels out the greater loft per weight of the down. My ski buddy has the montbell UL pants, and so far as we can tell they are not as warm as my pants, though they are lighter. If I were purchasing pants rather than making them, I might go with down for the expected greater longevity, but if making my own I would stick with the synthetic. I never wear mine except in camp – they'd be way too warm for me if on the move – so they are very unlikely to ever get wet. Thus the moisture issue is a non-issue for me. I alos made a jacket at the same time using the same materials as the pants, and the deciding factors were the same, except that I do use the jacket during the day at lunch and other stops.

So aside from the question of down vs synthetic for pants(which you all are making really hard to choose), what does everyone prefer as far as getting them on?

I'm been leaning toward full side zip despite the extra weight, as it makes them the easiest to get on. I supposed though 12" or so ankle zips would work as well since you'd probably be taking off snowshoes/skis during the rest stops/around camp when you'd be putting them on.

No zips at all don't seem to make a lot of sense to me as that requires de-booting, and that isn't a lot of fun in the snow.

And who makes full side zip insulated pants besides FF (down) and BPL (synthetic)? The new MB TEC pants are full zip, but I can't figure out on the Thermawrap or UL Down pants are. The ID PlQ pants appear to have no zips.

Opinions?

"And who makes full side zip insulated pants besides FF (down) and BPL (synthetic)? The new MB TEC pants are full zip, but I can't figure out on the Thermawrap or UL Down pants are. The ID PlQ pants appear to have no zips."

The Thermawrap are full zip as are the Patagonia Micropuff pants (synthetic) and the WM Flight pants (down).

The WM Pants are now posted on their WM website.

"I'm been leaning toward full side zip despite the extra weight, as it makes them the easiest to get on. I supposed though 12" or so ankle zips would work as well since you'd probably be taking off snowshoes/skis during the rest stops/around camp when you'd be putting them on."

Maybe yes, maybe no. Generally at rest stops I don't remove skis or snowshoes. When I stop at camp, the first thing I do is throw on insulation, and the second thing I do is stomp out a platform for the tent, which requires the snowshoes. I'll also put them on if I'm crossing a ridgeline. Having full side zips is a real advantage.

MB changed their design this year. They are 7/8ths zip. They zip up to the pockets. The Thermawrap pants are real easy to get on and off with shoes, but you would have to take off any snowshoes and be real careful if your shoes are muddy.

I’m probably going to get myself in trouble here, as I barely passed high school algebra, and stopped math classes after the one required my freshman year of college, but judging by this chart(One of the most useful things ever posted on BPL), Powerstretch fleece is equivalent in warmth to the MB Thermwrap. Of course, this was comparing tops, but if I believe(and someone will correct me if I’m wrong) the value’s can be compared, as the Thermawrap jacket and pants use the same amount of insulation.

I went back and looked at this because I have a pair of 100wt Powerstretch tights I picked up cheap at Sierra Trading Post, as wear as a pair of 100wt microfleece tights(62.5% as warm as the thermawraps if I read the chart correctly). These two things each weight ~6oz according to the manufacturer(don’t have a scale to weigh them myself. The Thermawraps weight 10.2oz, probably due to the zippers, I’d guess.

Of course the zippers provide the advantages detailed above, but it you don’t have the budget for the Thermawraps, or UL Downs(which by the same chart would likely be 3X the warmth of the Thermawraps or Powerstretch.) and you were just wearing them around camp and to bed, the Powerstretch tights could be a much cheaper alternative. I got mine with an email list discount for $35 shipped from STP. Having to take off your boots might be a hassle, but I figure at the least, it’s a cheap way to experiment and figure out what kind of garment warmth I need.

I have no zips on mine, and don't feel the need. I never put them on except in camp, after the shelter is set up and the boots are off for the day. During the day, putting on a warm jacket and hat always keeps me warm enough through lunch stops.