I have a pair of old Koflach plastic boots and I replaced their inner boots with custom Palau liners that are a lot thinner and lighter but are supposed to be very warm - not tested that yet. Since that frees up some space between the liner and the plastic shell, I'm thinking about adding some ground insulation (my feet tend to get cold easily). Basically, what about cutting out an extra insole out of closed-cell foam and placing it between the shell and the liner? (in addition to regular insole worn inside the liner). Has anybody tried that? Any opinions on which foam would be both warm and durable enough for this purpose?

Closed cell foam will pack down to nothing very quickly, I had a partner who tried it. Try cork, you can buy it by the roll.

Thanks, that's a good idea. I think flooring cork comes in tiles, but they might be to short for my bigfoot feet.

For my Trezeta TFK 201 double boots, I fabricated three extra layers: cork, EVA foam and tin. All three are very thin, so the three of them together still fit without any problem between the liner and the shell.



The cork one adds thermal insulation and possibly some damping.
The EVA foam one I cut from an old and extremely thin camping pad. It makes the boot warmer and the walking easier on the knees, as it provides a level of shock absorption.
The idea behind the paper-thin tin layer, is that it reflects the cold of the glacier back down, and the body heat back up. Or something along those lines. You'll need tin snips for this.

Initially, I had only the cork and the tin layer. Adding the EVA foam one definitely made the walking more comfortable (though still not as comfortable as my wonderful Lowa Civetta Extremes, which I bought later).

Experimentation showed, that the best order for me is (top to bottom) tin, EVA foam, cork. With the rough foam on top, it is very difficult to get the inner boot in or back out of the outer boot.

I had extra space in my La Sportiva G2SM and just placed a superfeet insole ontop of the existing insole. Of course they're men's boots so my women's feet are a bit small thus I had the room. They fit perfectly now.

Apparently boot manufacturers think women don't climb mountains, no one makes a women's boot for high altitudes......

Thanks a lot for the collective wisdom, folks. Glad I asked.
Buckle - frankly, I couldn't begin to guess what gender the Koflach boots are made for.