I have a question about the temp ratings of a sleeping bag. If I buy a 20 deg bag can I decrease the rating to say 0 deg by adding a poly fleece liner or will I not get that much benifit? I have 3 bags now, one is an old military extreme cold weather bag, I've never gotten cold in it even down into the teens but it's very heavy, I have a 30 deg summer bag really light weight but still bulky and cheaply made, and I have a mummy type sold by REI but I don't know its rating as it was giving to me because someone didn't want to backpack anymore, they cut all the tags out of it but don't remember the temp rating. I've used the REI bag down into to teens and wasn't cold but then again I wasn't warm either. I thought about a poly fleece liner to the REI bag but would just as soon get a new bag instead. Any ideas?
Adding fleece liner adds 10 degrees A removable, machine washable liner is needed for any sleeping bag, simply to keep the bag clean. Use a light nylon "bug bag" in summer or fleece in winter. Adding a fleece liner reduces useable temperature comfort rating by about 10 degs. F. Adding a wind-proof, water-proof, breathable Gore Tex outer protective bag adds about another 5 degs. F. Wearing an insulated head covering, such as a balaclava, dry socks and mittens to reduce heat loss through the top of your head, feet and hands adds another 5 degs. F. If you don't have one already you want a Gore Tex clothes bag to take off the clothes you were wearing during the day. Bring the clothes bag into the sleeping bag with you and they will dry overnight. For winter ops wear silks next to the skin to reduce abrasion and when sleeping wear light weight merino wool or polypropylene long underwear over them. Keep a separate just for sleep wear, while your sweaty ones dry overnight in the clothes bag which doubles as a pillow.
If the one you have is a true extreme cold weather millitary mummy bag then your good for a while. When we went camping in Fairbanks at -70 I dressed in my carharts then into an arizona 20 above sleeping bag. I just about froze.. My friend on the other hand climbed into the military sleeping bag, with a wool military blanket around him and extreme cold weather longjohns on and zipped up the bag. He was totally toasty all night long... Yes it really was -70 we were testing our equipment. I sort of refabed mine after that... I think I have about 5 of the military mummy bags now. They have some sort of cover to keep them warmer... they have the bottom layer is some sort of quailofill or something like that and the top is down.. I have actually used them at many different temps up here... I like them, even the old ones.
The temp. rating on sleeping bags are mostly wishful thinking on the manufacture's part. The rating do act to give the buyer some idea of what temps the bag could be used, but only generally. Much depends upon a variety of conditions, including the age, health, etc. of the user. Any added liner bag or additonal outer shell will certainly drop the temp. rating of the bag. The addition of a stocking hat, gloves, dry socks as the previous poster said will act to further increase your warmth/comfort level. Remember, buy quality and only cry once!
We have a layered system for each of us. 1. Outer covering gortex to help keep the bag from getting wet. Also aids in the temp rating of the bag. 2. main bag rated at about +30 to +40 3. Inner bag liner which can be used alone for much warmer temps or in conjunction with the other two for a 0 to -20 rating. 4. and for me because I'm cold blooded, I've also added another layer. I have a flannel sheet and a silk bag liner.
