Does damp make a difference?

  • Hey Guest, We've had to cancel our 2020 Summer BushMoot PLEASE LOOK HERE for more information.

Sub5mango

Tenderfoot
Oct 13, 2019
92
12
52
East Anglia
I just spent the night out in my new snugpak elite 4 sleeping bag rated comfortable -10°c. I used a spacious bivi bag and a decent thermarest mat. I wore a moreno wool base layer and a hat. I had a tarp set up as standard A over me. The grpund was already soaking. I went to bed warmish. There was a extremely light wind blowing across me. It rained all night but I remained perfectly dry and no condensation inside bivi bag in the morning.

Overnight lows were only +5°c. I wasn't exactly cold but not super warm either. I certainly didn't feel like I would be comfortable at -10°c, the bags comfort rating.

Am I missing something?

(Nb I sleep at home with the window open and no heating on in bedroom).
 
Last edited:

Nice65

Full Member
Apr 16, 2009
4,769
1,384
55
W.Sussex
There’s also the possibility that if the mat is bulky it’s reducing the possible loft of the sleeping bag inside the bivibag if it’s a tight fit.
 
  • Like
Reactions: Sub5mango

Sub5mango

Tenderfoot
Oct 13, 2019
92
12
52
East Anglia
I
There’s also the possibility that if the mat is bulky it’s reducing the possible loft of the sleeping bag inside the bivibag if it’s a tight fit.
Thanks but the bivi bag is spacious, plenty of room for the mat and the bag without the loft being compressed.
 

Sub5mango

Tenderfoot
Oct 13, 2019
92
12
52
East Anglia
More insulation underneath? Perhaps damp ground will suck warmth more than dry ground .
Thanks. I was thinking of adding a small wool blanket or one of those compress foam mats but I thought with a sleeping bag comfort rating of -10 I should be well comfy at +5 with my existing set up :(
 

C_Claycomb

Mod
Mod
Oct 6, 2003
5,776
859
Bedfordshire
Temperature ratings are aimed at tent campers. I even heard somewhere they were often aimed at people sharing a tent. You go solo under a tarp with the wind blowing past, and it is going to be a good deal cooler. The temp rating isn't that you will be comfortable when the air immediately outside the bag is X temperature. Its the outside temperature and it is assumed that you are inside an enclosed shelter.

I have always been cooler under a tarp or in a hammock than the temperature rating of the bag or quilt would suggest.
 
  • Like
Reactions: Toddy and Sub5mango

Sub5mango

Tenderfoot
Oct 13, 2019
92
12
52
East Anglia
Temperature ratings are aimed at tent campers. I even heard somewhere they were often aimed at people sharing a tent. You go solo under a tarp with the wind blowing past, and it is going to be a good deal cooler. The temp rating isn't that you will be comfortable when the air immediately outside the bag is X temperature. Its the outside temperature and it is assumed that you are inside an enclosed shelter.

I have always been cooler under a tarp or in a hammock than the temperature rating of the bag or quilt would suggest.
Thanks Chris. In this scenerio what do you suggest is the best way to go for increased warmth? Getter a warmer bag?! Bit late for that as I just got this one! Get a sleeping bag liner (thin fleece type or silk)? Use an additional mat underneath like a lightweight old school compressed foam? Get a better mat (any suggestions?) Use a wool blanket somehow? I'm trying to keep the weight down.

Also the bivi bag is a single hoop one which I use without the hoop. Am I better off getting one like an army one that has a face hole?
 

Sub5mango

Tenderfoot
Oct 13, 2019
92
12
52
East Anglia
There’s also the possibility that if the mat is bulky it’s reducing the possible loft of the sleeping bag inside the bivibag if it’s a tight fit.
Actually, I am now wondering if the bivi bag is too spacious. It is one of those single hoop ones which I use without the hoop. Perhaps I would be better with one of those army type ones with a facehole. What do you think?
 

Woody girl

Bushcrafter (boy, I've got a lot to say!)
Mar 31, 2018
2,802
1,899
62
Exmoor
A liner is a good idea. Keeps the bag cleaner aswell as adding warmth. As to which sort of liner is best, I'm told silk, but they are expensive. I do have a fleece one and it's quite cosy. Hate getting tangled inside the bag with it which can happen.
A foam mat is cheap and light. Could be a sensible extra insurance. The warmest foam mat I ever had was a black thick one I got from Springfields many moons ago. Cost about a tenner in those days. I think it was a military one. Excellent bit of kit.
 
  • Like
Reactions: Sub5mango

Sub5mango

Tenderfoot
Oct 13, 2019
92
12
52
East Anglia
A liner is a good idea. Keeps the bag cleaner aswell as adding warmth. As to which sort of liner is best, I'm told silk, but they are expensive. I do have a fleece one and it's quite cosy. Hate getting tangled inside the bag with it which can happen.
A foam mat is cheap and light. Could be a sensible extra insurance. The warmest foam mat I ever had was a black thick one I got from Springfields many moons ago. Cost about a tenner in those days. I think it was a military one. Excellent bit of kit.
Yea, I move around a lot and getting tangled up was one reason I didn't want to go the liner route. I thought I had my sleeping kit sorted!
 

Woody girl

Bushcrafter (boy, I've got a lot to say!)
Mar 31, 2018
2,802
1,899
62
Exmoor
Yep those liners can be a pain in the you know what !
Perhaps a woolen blanket wrapped around your bag would be
a) warmer
b) less hassle
)c more versatile
 

Billy-o

Native
Apr 19, 2018
1,306
520
Canada
I think it is difficult to make sweeping statements about all people with regard to sleeping temperatures. I sleep entirely comfortably in Autumn and Spring snow in a -10 down bag with a bivvy and a mat. Later on It'll be a -20 bag. But since I bought a very well insulated mat, and sleep in merinos and a hat, I often overheat.

My point is I am a warm sleeper and often kick the bedclothes off .. much to the delight of dearest wife who relishes the opportunity burying herself under as much quilt as possible.

So, there might be two things to consider, I suppose. First: when you say you went to bed warmish, is it possible you had been sweating and were damp when you turned in? Second: in the end, if you are cold with your current early winter bag, the thing is to get a higher rated one (or a quilt that you can cast over ... though from what you say about being a wriggler, maybe that wont work out).
 
Last edited:
  • Like
Reactions: Sub5mango

Toddy

Mod
Mod
Jan 21, 2005
35,781
1,863
S. Lanarkshire
How do I deal with it ?
I take a hot water bottle :D
Seriously, I do. It warms the bed before I get in, if it's well wrapped up it'll be a warm thing all night long. A decent wool blanket over the top of my bag, even if it does compress the loft a little, is a good thing too when it's cold and damp.
 
  • Like
Reactions: Sub5mango

Sub5mango

Tenderfoot
Oct 13, 2019
92
12
52
East Anglia
I think it is difficult to make sweeping statements about all people with regard to sleeping temperatures. I sleep entirely comfortably in Autumn and Spring snow in a -10 down bag with a bivvy and a mat. Later on It'll be a -20 bag. But since I bought a very well insulated down mat, and sleep in merinos and a hat, I often overheat.

My point is I am a warm sleeper and often kick the bedclothes off .. much to the delight of dearest wife who relishes the opportunity burying herself under as much quilt as possible.

So, there might be two things to consider, I suppose. First: when you say you went to bed warmish, is it possible you had been sweating and were damp when you turned in? Second: in the end, if you are cold with your current early winter bag, the thing is to get a higher rated one (or a quilt that you can cast over ... though from what you say about being a wriggler, maybe that wont work out).
Thanks. What is the mat you have?
 

Wander

Nomad
Jan 6, 2017
471
506
Here There & Everywhere
As someone said earlier in the thread - you compress the bag when you lay in it and this reduces its ability to insulate.
Hence the reason for ensuring you have a good thick layer between you and the ground.
Also, temperature ratings are extremes rather than comfort ratings.
You say you had your tarp pitched as an A. Was it open at both ends? If so, there's a chance it formed a wind tunnel which encouraged the flow, and therefore chill, of the wind. Closed at one end would be better.

In summary, maybe a mattress of thick spruce/pine boughs (at least a foot thick) on which to put the bag, plus a closed tarp, might improve matters.
Apologies if you were already aware of these things.
 
  • Like
Reactions: Sub5mango

Sub5mango

Tenderfoot
Oct 13, 2019
92
12
52
East Anglia
As someone said earlier in the thread - you compress the bag when you lay in it and this reduces its ability to insulate.
Hence the reason for ensuring you have a good thick layer between you and the ground.
Also, temperature ratings are extremes rather than comfort ratings.
You say you had your tarp pitched as an A. Was it open at both ends? If so, there's a chance it formed a wind tunnel which encouraged the flow, and therefore chill, of the wind. Closed at one end would be better.

In summary, maybe a mattress of thick spruce/pine boughs (at least a foot thick) on which to put the bag, plus a closed tarp, might improve matters.
Apologies if you were already aware of these things.
Thanks. There isnt usually the boughs available so that's not an option unfortunately. However I did have both ends open and both sides for that matter! Part of the reason for going the tarp route is to be more open to nature (and it's fun!). I could try setting it up with a couple of sides closed though. Any recommendations for pitch format which gives reasonable shelter but doesn't become a tent? (I have one of those and it's lighter than the tarp and bivi and extra bedding! combo)
 

Ruud

Full Member
Jun 29, 2012
662
166
Belgium
www.rudecheers.wordpress.com
My two cents:

I use an inflatable Thermarest which I use in conjunction with a cheap Z-style Karrimor foam mat. The Karrimor foam mat can be used to sit on, be used as a kneepad in a canoe and so on and doesn't add any noticeable weight to your pack actually. It is especially great to lay on during breaks on longer hikes. It adds a tremendous amount of comfort for its price and weight. In summer I lay my Thermarest inflatable on top of the foam mat to keep it safer from needles or other sharp ends. In winter I lay the foam mat on top of the Thermarest, as it is good practice to lay on the warmest (highest R-rated) mat you have with you.

Ever since I use a Sea To Summit Xtreme Reactor liner I've slept so much better. Less chill in the mornings, a second layer to pop over your skull... The fabric is pretty stretchy, I don't feel like I'm getting tangled in it. You might want to try a cheaper version to test out wether it works for you or not (the entanglement).

I don't think you need to make any changes in regards of your bivybag.
 

Sub5mango

Tenderfoot
Oct 13, 2019
92
12
52
East Anglia
Thanks. There isnt usually the boughs available so that's not an option unfortunately. However I did have both ends open and both sides for that matter! Part of the reason for going the tarp route is to be more open to nature (and it's fun!). I could try setting it up with a couple of sides closed though. Any recommendations for pitch format which gives reasonable shelter but doesn't become a tent? (I have one of those and it's lighter than the tarp and bivi and extra bedding! combo)
Actually on further thought, I need to make changes to the sleeping kit rather than the tarp as I want to keep the "open" experience.