Thermals or silk liner ?

A silk liner adds 2-3F tops.

The silk bag liner primarily keeps your bag clean.

–B.G.–

You hit on my rationale for switching from a liner to silk-wt long johns when you said "duel use". My thermals act as my second set of clothes and the bigger bonus may be how much more comfortable I am wearing them then sleeping in a liner. I don't have the answer as to which would be warmer. The liner may retain more heat but the thermals manage moisture and decrease evaporative heat loss. I think the appropriate question may be not which is warmer but would the difference be noticeable? My thoughts are that the difference would be negligible and thus issues of comfort, weight/dual use, etc., would be the deciding factors.

I use both.

A silk liner has two functions:
1) keep the bag clean
2) block drafts

Never forget the second one!

Cheers

I used a liner for a long time, but I always found it somewhat uncomfortable due to tangling up while I rolled around all night. I switched to silk long underwear, which weighs just about the same for me (4 oz for the liner, 5 oz for long underwear), and was very happy with it. Like Roger, I also used the liner to keep my sleeping bag clean, but I only wore the long underwear in the sleeping bag and in camp, so it should keep body oils off the sleeping bag the same as a liner (in theory).

I didn't find any real difference in warmth between the liner and the long underwear.

I suppose one could weave a fabric thick and heavy with silk — but most all silk garments are thin and light and permeable — just the thing for summer use — and bag liners come that way too.

The thin liner can block blowing wind, but its very thinness does little to block any cold air from permeating right through. The piece that's doing the real blocking is your sleeping bag. If you cinch your sleeping bag carelessly, for example, and let in the cold night air, you will soon feel it right through your silk liner.

So yes, the theory about a liner enveloping more space is true. But it doesn't trap air movement all that well — so cold air can work its way through and your warm body heat can easily go the other direction as well. That you haven't actually feel this is a credit to your sleeping bag, actually.

Again, if you are looking for a temp boost, don't expect more than 2-3F. Which reminds me of Sea-to-Summit's cleverly named "Thermo Reactor" bag liner — with a LOUD CLAIM of 15F boost! Don't believe them. That POS is good for 3-5F — tops!

I also have a thermo reactor my experience is if your bag blocks any wind and drafts that the liner adds about 10 but if you don't have a draft tube or your hood isnt chinched down then the liner does nothing unless you can stop all drafts if you can do that it works pretty well but all it takes is you moving around and the draft tube lifting up and it makes the liner almost useless

I moved to long silk underwear, socks, and beenie to keep the bag clean and use them only for sleeping/camp. They do little to stop drafts and add little warmth, but I couldn't stand the liner wrapping around me in the night as I tossed and turned and flopped from side to back to side.

Lately I have been thinking about just wearing a shirt and pants made of momentum or pertex quantum. Similar weight and perhaps more draft protection as well as a bit more bug proof around camp. Another hiker I know wears a disposable tyvek jump suit as sleeping/camp wear and loves it.