Hi all,

My girlfriend and I will be camping over Easter, and the forecast says ~1C at night. Our sleeping bags are rated for 5C comfort and our inflatable pads are non-insulated. We'll be in a big and comfy tent, and hopefully will camp in the woods, so wind is not a problem. I previously carried a foldable car windshield sun shade to put underneath our pads, horizontally, covering the area under both torsos. It improved our sleep on a 8-10C night compared to a slightly warmer night without the sun shade. For this trip we will also take disposable heat packs and will probably sleep in our light down jackets. Any other (cheap) tips and tricks? Everything up to "wrap the tent in tin foil" will be considered

Thanks!
Tom

Buy a couple of half decent CCF mats to replace the windshield thing maybe.

Hot food/drink just before you get into your sleeping bags.
If possible, put the windscreen sun-shade or some other closed cell foam on top of the sleeping mats (uninsulated mats can lose heat via convection within the mat, putting the insulating material between you and the mat helps prevent this).
Wear a hat.
Use reusable rather than disposable heat packs.*
Thermal tights/long johns.

*Warm glow of being more environmentally friendly.

Take a sleeeping bag rated for the temperatures you will experience
Wear more clothes to compensate for this not being the case or closed foam etc

Dont take disposable heat packs - i would go as far as say dont take heat packs

Share body heat

Thanks for all of the comments.

Will try the sun-shield on top of the pads (unless too slippery). Thanks for that! Forgot to say that our sleeping bags can be joined, so will probably do that to share body heat. Extra clothes and beanies for sure, and will eat and have some tea just before sleep. Wasn't aware that there are reusable heat packs. Looking at these now. Any specific brand / property I should check or just get something from amazon?

BTW, what's the argument for CCF mat compared to the sun-shield if the only goal is insulation. I'm under the impression that the later insulates better, while being lighter, and less bulky. Also, one fits two torsos exactly.

The sun shield doesn't insulate* (prevent conduction) - it's designed to reflect light, but it will also reflect heat radiating from your body back to you by the same mechanism, which is why it helps, but minimally compared to something that insulates you and stop conductive heat loss, like a CCF mat (and the CCF stops heat being transferred from one side to the other by convection, which your inflatable mat doesn't as much).

I would second the "don't bother with heat packs" advice. Fine for warming hands or feet for a short period; pretty minimal effect on a whole body for a long period.

Edit: forgot
*on a car windscreen in might trap a bit of air underneath which will insulate the windscreen, which helps stop it freezing, but it won't trap much air with two bodies on top of it squishing it into the ground.

Eating foods with a high fat content before bed is supposed to help. A Nalgene or Kleen Kanteen can be used as a hot water bottle. Vast amounts of alcohol.

A heat pack located over the femural artery in the groin will help by warming the blood which then circulates around the body.
Heat holder socks and full length thermals.

In my experience joined sleeping bags are generally less warm as you can't draw them up tight around your head and neck. You inevitably end up with a gap which will let cold air in and warm air in.

Also, if you are wearing too many layers then you'll be preventing any heat from getting into the bag insulation to "loft" it, making it pretty useless.

I've found having the bag unzipped reduces the chances of cold spots where its stretched over bits of you - using it like a large quilt. Plus you can get away with wearing more clothes underneath without the problem Scotroutes mentions. Does rely on good insulation underneath though.

In addition to hats, I find that some sort of scarf or other thin, loose material draped over my face and neck helps. It warms the air around the face and that I breathe in, whereas otherwise that cold air often bothers me and keeps me awake. Less of an issue in a tent than in a bivvy bag.

Also, if you are wearing too many layers then you'll be preventing any heat from getting into the bag insulation to "loft" it, making it pretty useless.

I often wonder about this, as I've read it elsewhere. Assuming the heat you're after to stay warm is coming from your body, surely it doesn't matter what traps it? If none reached your sleeping bag due to clothing, that shouldn't matter (other than you've carried a bag you didn't need)??

Draping the jacket over the bag rather than wearing it can be warmer if you can get it to stay put..

Invest in some sleeping bag liners and run around/do some star jumps, press ups or sit ups just before getting in bag, just enough to warm you up, you don’t want to get sweaty as this will make you cold later

Verena wrote: ↑Wed Mar 31, 2021 6:54 am In addition to hats, I find that some sort of scarf or other thin, loose material draped over my face and neck helps. It warms the air around the face and that I breathe in, whereas otherwise that cold air often bothers me and keeps me awake. Less of an issue in a tent than in a bivvy bag.

I'm not saying I disagree but I actually love the feeling of cold, fresh air on my face when I'm otherwise toasty. It's one of the pleasures of winter bivvying.

Verena wrote: ↑Wed Mar 31, 2021 6:54 am In addition to hats, I find that some sort of scarf or other thin, loose material draped over my face and neck helps. It warms the air around the face and that I breathe in, whereas otherwise that cold air often bothers me and keeps me awake. Less of an issue in a tent than in a bivvy bag.

A similar thread cropped up a while ago. Amidst all the recommendations about hot food, hot drinks, jumping around etc, I followed Verena's line of thought. The surface area of lungs is apparently about half the size of a tennis court, with direct access to the blood circulating your whole body. Breathing, say, 6 times a minute, you're exposing your bloodstream to freezing air ALL night. Somehow pre-warming that air must help? Biologists?

boxelder wrote: ↑Wed Mar 31, 2021 7:26 am

Also, if you are wearing too many layers then you'll be preventing any heat from getting into the bag insulation to "loft" it, making it pretty useless.

I often wonder about this, as I've read it elsewhere. Assuming the heat you're after to stay warm is coming from your body, surely it doesn't matter what traps it? If none reached your sleeping bag due to clothing, that shouldn't matter (other than you've carried a bag you didn't need)??

That seems like a self-defeating argument to me too Colin... if the bag isn't lofting because your clothing's trapping all your heat within, surely that's a good thing? And if the bag isn't providing enough insulation because it's not lofted, then it must be allowing heat to escape, heat which will cause it to loft.

Only if heat were bypassing the bag and therefore not lofting it - say by escaping through an opening - would it be a problem.

It's a problem when the Dew Point is within the bag as you then end up wrapped in a damp layer, which then dampens the clothing you are wearing.

Ah, yes - that's a different issue though.

thenorthwind wrote: ↑Wed Mar 31, 2021 9:55 am

boxelder wrote: ↑Wed Mar 31, 2021 7:26 am

Also, if you are wearing too many layers then you'll be preventing any heat from getting into the bag insulation to "loft" it, making it pretty useless.

I often wonder about this, as I've read it elsewhere. Assuming the heat you're after to stay warm is coming from your body, surely it doesn't matter what traps it? If none reached your sleeping bag due to clothing, that shouldn't matter (other than you've carried a bag you didn't need)??

That seems like a self-defeating argument to me too Colin... if the bag isn't lofting because your clothing's trapping all your heat within, surely that's a good thing? And if the bag isn't providing enough insulation because it's not lofted, then it must be allowing heat to escape, heat which will cause it to loft.

Only if heat were bypassing the bag and therefore not lofting it - say by escaping through an opening - would it be a problem.

Mind to explain why heat lofts a down bag? I guess reading this, one would believe, that cold temperatures don't lead to down lofting?

holdsteady wrote: ↑Wed Mar 31, 2021 8:49 am run around/do some star jumps, press ups or sit ups just before getting in bag, just enough to warm you up, you don’t want to get sweaty as this will make you cold later

I usually find that all the faffing setting up camp and getting into my sleeping/ bivvy bag has just that effect

Alpinum wrote: ↑Wed Mar 31, 2021 12:44 pm

thenorthwind wrote: ↑Wed Mar 31, 2021 9:55 am

boxelder wrote: ↑Wed Mar 31, 2021 7:26 am

Also, if you are wearing too many layers then you'll be preventing any heat from getting into the bag insulation to "loft" it, making it pretty useless.

I often wonder about this, as I've read it elsewhere. Assuming the heat you're after to stay warm is coming from your body, surely it doesn't matter what traps it? If none reached your sleeping bag due to clothing, that shouldn't matter (other than you've carried a bag you didn't need)??

That seems like a self-defeating argument to me too Colin... if the bag isn't lofting because your clothing's trapping all your heat within, surely that's a good thing? And if the bag isn't providing enough insulation because it's not lofted, then it must be allowing heat to escape, heat which will cause it to loft.

Only if heat were bypassing the bag and therefore not lofting it - say by escaping through an opening - would it be a problem.

Mind to explain why heat lofts a down bag? I guess reading this, one would believe, that cold temperatures don't lead to down lofting?

That was Colin's assertion, I was just going along with it. I guess if you warm the air trapped within the shell, it expands, allowing the down to loft. In theory - practice could be completely different. I certainly wouldn't argue that a cold bag doesn't loft though!

The down lofts by being dry and loose in the baffles. It doesn’t loft under your body(it’s crushed) if it’s old and damaged or if it’s wet.
Loft creates a network of tiny air pockets within the down and this is what traps your body heat. The body heat itself doesn’t fluff up the down.
Probably a simplistic explanation but i’m pretty simple anyway.