is this useful even if you do use a pack...
is this useful even if you do use a pack with an insulated sleeve? would this help avoiding frozen tube or mouthpiece a little bit more? I was thinking a hand warmer would do the trick of avoiding that, but maybe an extra layer of insulation would help, but also not sure if this would fit in the sleeve. It's a Karve 16 S/M
Basically, this will buy you some time. Once it gets below 20F, you'll still freeze up if you're not constantly sipping every few minutes. I've even tried using Armaflex, which is insulation for plumbing. Even with that, if I didn't drink enough to clear the tube it froze in 15-20 minutes
Since hydration pack drinking tubes are narrow, they freeze up in minutes once it gets below freezing. Even 1/2" and 3/4" plumbing pipes can freeze in minutes once it ets below 14*f. That seems to be the magic number when the frozen pipe calls come in.
So to end all this rambling, yes, it will keep the tube and bite valve from freezing as quickly as without. I figure it could extend the operating range ten degrees lower and/or for a couple hours more.