Just when you think you've got something sussed you find out you haven't.
Regular Forum readers may recall that I spent some time this winter experimenting with techinques for cold-weather camping. This included spending nights under canvas in sub-zero temperatures (one night down to minus nine centigrade) in an unheated tent. I learned the value of insulating layers both above (in the form of an adequate sleeping bag or bags) and below (in the form of insulating mats).
My experiemtnts demonstrated that SIMs provided good insultion under the sleeper but that in very low temperatures it was necessary to augment that insulation: in my case, I used traditional rollmats (sometimes called carrymats) and flattended heavy corrugated card cartons. So far so good: those initial conclusions still hold.
I went camping in the Chilterns this weekend as part of my Counties Challenge. As the weather was so warm and night-time temperatures were forecast to be around 8 to 10 degrees, I let my guard down. Instead of taking my recently-bought Alpkit down-filled sleeping bag, I made do with two of my synthetic-filled bags (one inside the other). More significantly, I dispensed with the sheets of corrugated card and extra rollmats. So this weekend I slept on one SIM (an Alpkit 'Wedge') on top of one rollmat.
It was dry night (barely any dew or condensation by morning) but due to the hillside location there was a breeze all night. The temperature was lower than forecast too - checking later on the Met Office website, the two nearest weather stations recorded 6am lows of 4.8C and 5.5C. So a chilly night rather than a cold one.
I awoke around 6am with the small of my back and my hips feeling uncomfortably cold (I was sleeping in just a T-shirt and socks). The rest of me - chest, limbs, hands and feet were fine. Because I needed the loo, I got up and got dressed. When I got back to the tent, I noticed that my keys weren't where I'd left them laying on the groundsheet beside my bed. So I started rootling about under the bed as they'd obviously slipped out of sight.
To my great surprise, the SIG (sewn-in groundsheet) under the whole bed area felt very warm to the touch. (Away from the bed, the SIG was, of course, cold to the touch). Raising the SIM and rollmat, I felt around carefully. The area which had been under my head and a thick pillow was barely warmer than the unoccupied areas of the SIG and the area that had been under my feet was also hardly warmed. But under my shoulders, body and upper legs the SIG (and, thus, the ground below) was very warm to the touch.
To be honest, during my cold-camping experiments it had never occurred to me to check for heat loss in this way. But at least now I have learned a useful lesson. A significant amount of my bodyheat had been leaking away below me all night and warming up the soil. No wonder I'd felt a bit chilly in the morning.
My conclusion is that the value of good insulation under the sleeper is even more important than I'd already determined. Further, I conclude that even 50mm (two inches) of trapped air in a high-quality SIM augmented by 8mm (quarter-inch) of foam rollmat provides inadequate insulation even on fairly mild spring nights. In future it's cardboard boxes and extra rollmats for me every time.
Oh help! I'm about to camp in night temperatures of probably 3 or 4 degrees and I reckoned that the Dozer with a roll mat underneath would be fine but I shall be feeling under my bed to check!
My number one rule of camping, learned the hard way, is Never underestimate how cold it can get at night.
Thanks, SC. You keep on experimenting on our behalf and we'll learn from your discomfort.
Quote: Originally posted by Tentz on 11/4/2011
Certainly cardboard underneath you is a good insulator, as rough sleepers in our cities will tell you.
I was caught up in the Heathrow fiasco before Christmas and spent a very cold night on a stone/marble floor in Terminal 3; the difference when you had some cardboard under you was amazing.....and I have to say that one of the foil blankets over you that they gave out was also great.
Thanks for the info. Skip. I've got the SIMs, and foam rolls mats too, but they take too much room up in the car. But in my job, I should be able to scrounge the best insulators available.
Interesting, I have noticed that there is sometimes condensation underneath our SIMS and I make sure that I lift them regularly to make sure that everything is aired. It hadn't ever occurred to me that this was body heat leaking away.
Hmmm, I do wrap a fleece blanket around my SIM to make it a bit less slippy but I've never put anything else underneath it and as I'm a pretty chilly sleeper maybe I ought to look into something else. I've got some rollmats but as my SIM tends to walk around the pod I'm not sure that the SIM would stay on the rollmat (do they?) and Hubby will think I'm completely nuts if I demand cardboard.
I wonder what difference the thin foam for under wooden/laminate floors would make?
Quote: Originally posted by missElaineous on 11/4/2011I've got the SIMs, and foam rolls mats too, but they take too much room up in the car.
Oh, they roll away quite slimly as a rule. Would they not slide under the seats?
Quote: Originally posted by missElaineous on 11/4/2011But in my job, I should be able to scrounge the best insulators available.
Three of the advantages of cardboard cartons are that are free, they pack flat on the floor of a car's boot, and that if they get damp or damaged you simply dump them in the campsite's recycling bins when you leave.
Quote: Originally posted by PigletandTigger on 11/4/2011...there is sometimes condensation underneath our SIMS and I make sure that I lift them regularly to make sure that everything is aired.
Yup, I reckon that'll be the moist warmth as you sleep condensing on the cold surface of the groundsheet
Quote: Originally posted by PigletandTigger on 11/4/2011... maybe I ought to look into something else.
Start with cardboard cartons because they are free. As to what hubby says - tell him you'll be much warmer and that you are saving money.
Quote: Originally posted by PigletandTigger on 11/4/2011 I'm not sure that the SIM would stay on the rollmat (do they?) ...
In my experience, yes. My SIM is fairly 'non-slip' anyway and the foam of rollmats is usually reasonably 'grippy'. If not, it's easy to fashion a couple of wraparound straps from webbing, velcro strip, elastic or even just twine.
Quote: Originally posted by PigletandTigger on 11/4/2011 ...I wonder what difference the thin foam for under wooden/laminate floors would make?
I've seen that recommended here on the UKCS Forums. It would certainly add to the insulation although I've no idea whether it would be more or less effective than the various alternatives.
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Topic: Sleeping warm - a valuable lesson
