Warmer inside a tent? yeah right!

[Michael M]

Empiricisms Rules

John

It amazes me that as a parent I should send my son to MIT for a degree in engineering whom may come to the same specious conclusions.

If common sense did not answer this question then empiricism would.

Remember our intellectual capabilities are only necessary to advance our genetic materials, somewhat like ateliers and other adornments.

They should not be taken to seriously

Michael CM


PS
5 to 15 degree warmer -- measured, of course!

 

[John H Swanson]

Time to chime in

Okay, Okay ... I appreciate all of your responses.

I too have see the difference in between the outside temperature and the inside temperature of tents, tarp closed leantos, and small cabins. Most of the time, the big differnces were because of big heat souces (stoves, lanterns etc.) In fact, I think I bought my little peak1 lantern more for it's ability to add heat and dry clothes than for the light it offers, though that's a nice added benefit. And I have seen the heat build-up with a bunch of people in a tent too.

I guess my original question comes from waking up and being cold. Running out to answer the call and not feeling that it was any colder outside. Now y'all know its hard to judge when when you're out there in your parka and booties.

I think the real reason for not seeing it much warmer inside the tent was because I was sleeping with the doors open to cut down on the frost build up. Maybe next time, I'll have to close them. BTW, if anyone's solved that problem, please let me know

I enjoyed reading about everyone's experiences/ explaination especially oldfogies comments of breathing.

Thanks.

 

[Tom H]

Frost solution

John,
I you sleep with a flexible dryer vent hose over your mouth and nose, running the vent out through the tent wall somewhere, all your respiration moisture will go straight to the outdoors. And other hikers will see that little chimbley pouring "smoke" and think you've got yerself a woodstove goin'. You'll be the talk of the town. Try it and report back with your results

 

[John H Swanson]

TomH,

... but wouldn't that reduce the temperature of the tent as the heat from by breath is going outside?

 

[Tom H]

You want it all, don't you!

Well, I suppose an imaginitive fellow could come up with a heat exchanger attachment for the dryer vent hose that would capture at least some of the heat. Perhaps an efficiency of 50% would be acceptable? Or do you want 100%? That might necessitate using a closed loop system with one end of the hose attached to the mouth and the other end attached well, somewhere else. Seems that would have some nasty drawbacks though

 

[John H Swanson]

TomH

Weight would be the issue, but the heat exchanger was actally in my mind during the whole vent subject. You know your an engineer when you start designing useless solutions to silly problems like this one.

I've overcome this entire problem and many other ones by simply avoiding overnights. Why camp overnight when you're only doing 16 hrs of hiking? Isn't that why they invented headlamps? Sometimes it's unavoidable ie. BSP.

 

[Papa Bear]

Re: Time to chime in

... because of big heat souces (stoves, lanterns etc.) In fact, I think I bought my little peak1 lantern more for it's ability to add heat and dry clothes than for the light it offers, though that's a nice added benefit ...

John

A nit-pick here. A stove or lantern may provide more heat per minute than the body, but the body will generate more total heat by far over the course of the night. Do the math: you run the stove for say 10 minutes or the lantern for say 30-60 minutes. The body is there generating heat all night. Your resting metabolism is around 2500 kcal per day so that's say 850 Kcal over an 8 hour night. That's close to 250 BTUs, a non-trivial amount. As mentioned in another thread that's eough to dry out damp socks and underclothes and IMHO (and experience) plenty to heat the tent without the benefit of stove or lantern.

The trick however is to keep the heat in but vent the moisture, so the best tent will 1) keep out the wind 2) keep in the heat 3) let out the moisture and 4) be just big enough. That's why good winter tents are expensive. Well worth it.

JMO
Pb

 

[jfb]

John,

OK, I'm an engineer and I understand why you might think that a tent body might not be such a good insulator. The nylon fabric is thin and covers a wide area, both factors that degrade the ability to hold heat in the tent. However, you must remember that the tent wall has a laminar boundary layer of air on each side, heat is transferred by conduction through the boundary layers and air is a good insulator. So there's more insulation there than you can see.

You could do an easy experiment using an indoor/outdoor thermometer and a hair dryer. Set up the tent in your backyard with the outdoor bulb in the tent along with the dryer hanging from the ceiling. From outside the tent, plug in the dryer until the tent warms up several degrees, then unplug the dryer and watch how long it takes for the tent to cool back down to outside temp.

 

[John H Swanson]

Choosing a winter tent

jfb,

I pulled out the ASHRAE handbook last night and did some heat loss calculations while watching the snow fall.

I used the design on my Eureka Alpine meadows 3 season tent for the physical description because that's what I own.

It was interesting to see the heat loss diffeience on the single walll ends without the dead air space and extra boundry layers vs the double wall sides. The enlightenment for me was the need for full double walls throughout if you want to have a warmer tent. Obviously it could be either a dome design or vestibules ... and of course a fly that reaches the ground or mounding snow as previously mentioned.

Also, I was amazed at how difference between the outside and inside temperature drops off with a light (5mph) wind. Meaning a 15F difference with still air drops to a 7F difference with 5mph. Of course it's greatly affected by the single wall ends.

If nothing else, the exersize and this post has me prep'ed for choosing a winter tent