Is it colder to sleep in a car or a tent?

hmmm….thanks for the multitude of replies. I’m liking the tent ‘logic’ in most cases actually. I was really surprised how cold it was, given that I had two thermarest type things, a duvet, and the dog sleeping bag / blanket in the end!

Tent in the back of an estate car

Mini inside a big tent

i slept in the back of a van in Afan on sat night found it was a bit cold … woke up and some guys in a tent next to us were in the car with the heaters on ….

We sleep in our Van all the time and it definitely seems warmer than sleeping in a tent. One heck of a lot less hassle too!!

Our van is fully carpeted etc tho, which might make a difference?? We also sleep on a platform which is well off the ground and has great insulation under our bodies.

metal car will radiate heat to space much more readily than a fabric tent which’ll convect heat away.

Temp differential car-space is loads more than tent-ambient air so more energy lost and therefore colder in car. End of miserable thermodynamics refresher.

If you wanna stay in a warm vehicle, buy an Espace: they’re plastic.

OK so I need 100w of heat output, spread over an area and not exceeding the surface temp of a human – anyone donate lots of reptile heater pads?

What’s wrong with a 100w/60w light bulb? I think a 60watt light blulb will be enough.

Slightly OT – I don’t know if its an urban myth or not but I was told there was a case where a bunch of lads decided to sleep in a van overnight. They went to the pub, got bladdered, came back and crashed in the bag of van and shut the doors, with it having a bulkhead they all ended up asphysixiated.(???)

hot_fiat – radiative losses will be negligible in comparison with the size of convective loses due to air moving through the tent. For radiation from the car to be more than the tent you’d need a) a larger surface area and b) for the car to be at a temp higher than the tent – I dont think its sensible to assume you’d raise the temperature of the skin of the car by more than a fracton of a degree by placing a human inside it.

milkie – 100w from a lightbulb = one very hot spot with high convective loss at that point, different to 100w (the supposed value of heat from humans) over a larger surface area due to lower surface temp.

scotabroad – suppose it’s perfectly possible if the bulkhead is sealed properly and the door seals work, and there are no vents in the rear. I dont know how accurate any of those assumptions are though.

I have a cheap and nasty tent and it is without doubt warmer than the car in similar conditions.

In fact, and here is a scientific test for you… I once slept in the car to allow a mate to have his way with a lady in our tent. He messed it up, she left and he slept alone in the tent.
We had the same sleeping bags, it was identical conditions and I woke up freezing and he was toasty warm.

Not really a scientific test – I’m often toasty when my missus is freezing in the same tent with the same bag and roll mat.

In true mythbusters form I’m going to do this with a 100w bulb I think. Problem is going to be getting the power to the car as it has to be parked on the road. I can only really do this over two nights though so I’ll have to pick two nights with similar ambients and wind. Give me time!

I know it is not a scientifc test… did you not pick up on the sarcasm!?

Still, in my experience tent = warmer given the same or similar conditions.

large areas of single pane glass should give you a clue as to why cars get pretty dang cold.

No, I didnt 🙂

And large areas of single pane glass are a damn sight better than large areas of air-porous fabric. If I asked you to replace your single-glazed house windows with a thin layer of mulsin would you think it woudl be warmer?!

OK, I’m not a scientist or anything but I am a Military arctic survival instructor and one of our golden rules is never to sleep in a vehicle if there is a tent available, possibly for some of the reasons hot fiat says.
I am talking about severely cold conditions here (-15 and below), my personal experience (several trips to Norway) would tell me to go for the tent every time. as an example, I once broke down in a BV oversnow vehicle and had to wait a day for recovery, it was fookin orrible! as for a bottle of water never freezing in a vehicle, seen it several times.

A lot will also depend on what you are sleeping, i.e. how well insulated you are fom the ground otherwise your body will always try to heat up it’s suroundings or anything it is in contact with. This could include a car interior which is designed to be heated, not to insulate.

This probably hasn’t helped at all but I feel better now.

Correct me if I am wrong but I don’t believe that any successful attempts on Everest or either of the Poles have involved the use of a car for overnight shelter. Given that you don’t have to put up with trying to erect a car in the teeth of a howling gale there must be some very good reason why these people use tents instead of cars. The only logical conclusion that I can come to is that tents are warmer than cars.

However I once spent a weekend on Dartmoor in early February with snow on the ground spending one night in the tent and one in the car. There were four of us with a Mini Metro and a two man tent so we rotated the sleeping. The car was warmer. So I learnt from that experience that one should always check that the doors zips of your tent actually work before heading for anywhere remotely cold.

When I used to go out on the lash to various places in my yoof I always used to pack a sleeping bag just in case.

Spent many a warm and cosy night sleeping in my Honda CRX, saying that the leather seats made it really comfortable. Always cracked a window a little though.

Saying that I have also often cooked my ass off in a small 2 man tent on more than a few occasions

I reckon the vehicle is colder, especially if it’s a van with a metal floor. The air circulation underneath is wot cools it down so much. Surface to volume ratios and all that. I’ve been far colder in a car thatn in a tent, in similar conditions.

Another vote for tent being warmer. Can’t be bothered to do any science – sorry, there’s already enough contradictory stuff in this thread that I’d just be adding to the noise. Have however done both numerous times and speaking from experience. Mind you, I’m guessing some of you are sleeping in the seats in a car, whilst I’m using the 1.8m of flat floor I get in the back of mine with seats folded, along with a thermarest. Have done the car thing more than a tent recently, as it’s just so convenient, and I have winter weight sleeping bags.