Loc: Northern KY USA
I wonder if anyone has experience with these. I was looking for a Big Agnes Overbag to use with my bag at a store in Lexington KY that carries BA products. The manager suggested a Sea to Summit Thermolite bag. Some are rated to add 40 degrees to your existing bag, of course provided you're using a mat, which I do. Thier claims are this. Fits inside of your primary bag. Much lighter than an Over Bag/Sleeping Bag Combo. Various bags rated 25 - 40 degrees additional protection in cold. Extends the life of your current bag by keeping skin oils and persperation away from your bag. Can be use seperately as a mild/warm weather bag. Small, lightweight, and fits into a small stuff bag. Costs around $69 - $70, depending on chosen model vs. up to 3 or 400 bucks for some Over Bags that are bulkier, and heavier, and larger than your primary bag.
Hoping to find someone here that has had experience with these. Do they live up to their claims? Pretty lofty claims if you ask me, but I have no idea. $70 bucks is a great deal if they really do the trick.
Tom, never thought I'd disagree with you, but as a member of MEC, I can't let this one go by. At the upper left of the website it says Mountain Equipment Co-op. Sorry to do that to you, but it may be important for some. Suspect Phat may be right behind me. The lifetime membership today I believe is $15 (I paid $5 -- yes it was several years ago). best, jcp
I've never used one, but everything I have read online is pretty dubious about those claims. They say at best you can add 5-10 deg. unless the liner is a vapor barrier layer. You can get quite a bit of additional heat retention with a vapor barrier layer, but they aren't very comfortable and there is an art to using them.
Think about how much down it would take to add 40° to a bag. If a bag manufacturer could get rating with a thin layer of cloth instead of expensive down, they would do it in a heart beat.
Loc: Gateway to Columbia Gorge
A few ounces more of down in the sleeping bag is a lot warmer and lighter than any liner around! My experience with a silk liner was (1) it wasn't any warmer than without the liner and (2) it took me several minutes to get untangled from it so I could exit the sleeping bag in the morning. A couple times of that nonsense and the liner went into the trash.
I'm having a couple ounces of down "overfill" added to my Western Mountaineering sleeping bag this winter. WM charges only $20 plus shipping for this service.
Edited by OregonMouse (09/19/1208:35 PM)
May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view--E. Abbey
Tom, If it comes to a dope contest, I've got you beat hands down. I have very much appreciated your input over the years. It was just that I'm rather partial to MEC, and didn't want anyone to get an unfortunate surprise when dealing with them. No big deal at all. best, jcp
Guess I could be mistaken but I think you should check the entire AMK "blanket" product line, I think you will find they do offer thermo-lite. Rechecking again and I think it is called now the Escape Bivvi, $50.00 retail.
Loc: Marina del Rey,CA
Hehehe. The thing that makes my gaffe even worse is that I have something from MEC. In my defense, I didn't buy it, but yes folks, the C in MEC does stand for Co-Op. Reminds me never to post late at night.
Don't get me started, you know how I get.
Loc: SF Bay Area, CA
My experience is that the warmth these liners added is exaggerated... and the salesman has got to be smoking something. The warmest liner I saw on the Sea to Summit website claims is 20F. Thermolite isn't magic. It provides less warmth per / oz than down, primaloft, Climashield or polarguard... I believe around the same the high loft fleece.
The lightest option would be to use a down bag or quilt that appropriately warm... but that might be cost probative. If you have a bit of extra room inside your bag then you can use either insulating clothing or a small quilt inside the bag to boast the warmth.
I use a quilt which works well to 35F when wearing a light fleece hat and summer weight base layer. When I add a down baklava, gloves, a mid-weight base, and a ultralight down vest I am good to 20F, or if I am using my warmest down jacket and insulating pants I am good to around 0F.
In the dead of winter I switch from my quilt to a down bag and my daughter uses my quilt inside her sleeping bag to boast it's warmth.
As others have observed.. the mylar emergency liners are not very comfortable but can add a surprising amount of warmth (especially when is very cold) due to functioning as a vapor barrier. If you are looking at <10F conditions a vapor liner is a good idea to preserve the insulation of your primary insulation, but I would want a material that is a bit more comfortable than mylar next to my skin... and for vapor barriers to function properly they need to be very close to your skin.
Loc: Northern KY USA
Thanks, but I need to correct a couple of things. The Thermolite EXTREME bag liner advertises 25 degrees, not 40, as I mistakenly posted. It's a fiber fabric, not mylar as someone suggested, and is advertised to be suitable to be as a warm weather stand-alone bag. Weight is advertized at 14 oz.
Hope this clears thing up. They do make a lighter version with less claimed performance (about 15 degrees I think and weighing about 8 oz.
Loc: Northern KY USA
Thanks for all of your input. Seems like the verdict is pretty much unanimous. They don't work. Glad I didn't have to spend $60 to learn that lesson.
For now, I'll just keep using my old military bag. Consists of two mummy bags and a multi-layered gortex bivy bag.
Rated for 40 below for 4 hours sleep.
But definetly not for the Lite Gear talk on a forum dedicated to light gear. If you pack the whole thing it weighs over 6lbs.! We don't get 40 below weather here, maybe wind chill of -15 or a little more, but I was hoping to take a winter trip to the Rockies, or even a guided trip in AK. It is nice and toasty when the weather here drops in the teens, but again it's not light weight, was designed for young strong troops, not middle aged men. The stuff "sack", would probably hold most peoples gear for a 3 day trip.
Plus it's a real pain to zip and unzip everything. Especially if nature calls in the middle of the night in the dark and possibly, snow. No fun at all.....