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3 Corrected errors in water production during sleep.
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YouEven if you don't feel yourself sweat about, you lose around 200g of water a litre at night through 'insensible perspiration' Assuming cold temps (below 0 C) you lose water to keep your lungs from turning into dried leaves. You exhale something closeincrease the humidity of the air you inhale to about 90% R.H. at 37 C. When you exhale you lose about 44 mg/liter of air you exhale. 12 one liter breaths per minute = 720 * 44 mg = 30 g /hour. May be more than that depending on how much your metabolism has sped up due to the cold. That

That moisture has to go somewhere, and at below zero temps, air doesn't hold much of it. You wake up with frost lining the tent, and your sleeping bag full of water vapour saturated air, likely with some amount condensed as frost on the inside of your sleeping bag.

You sweat about a litre at night. You exhale something close to that. That moisture has to go somewhere, and at below zero temps, air doesn't hold much of it. You wake up with frost lining the tent, and your sleeping bag full of water vapour saturated air, likely with some amount condensed as frost on the inside of your sleeping bag.

Even if you don't feel yourself sweat, you lose around 200g of water a night through 'insensible perspiration' Assuming cold temps (below 0 C) you lose water to keep your lungs from turning into dried leaves. You increase the humidity of the air you inhale to about 90% R.H. at 37 C. When you exhale you lose about 44 mg/liter of air you exhale. 12 one liter breaths per minute = 720 * 44 mg = 30 g /hour. May be more than that depending on how much your metabolism has sped up due to the cold.

That moisture has to go somewhere, and at below zero temps, air doesn't hold much of it. You wake up with frost lining the tent, and your sleeping bag full of water vapour saturated air, likely with some amount condensed as frost on the inside of your sleeping bag.

2 added case for tents. Some additional tips for winter camping.
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The usual limit in winter camping is how good your sleeping pad isYou sweat about a litre at night. If I'm anticipating really cold You exhale something close to that. That moisture has to go somewhere, and at below zero temps, I will bring twoair doesn't hold much of it. You wake up with frost lining the tent, and your sleeping bagsbag full of water vapour saturated air, one sizedlikely with some amount condensed as frost on the inside of your sleeping bag.

You can make a case for a tent:

A: It's constructed with vents near the top and bottom so that it can act as a chimney. It needs to fit overdo several air changes an hour to keep up with the other -- often justmoisture release of the occupants. In this case it's likely no warmer than outside. If you are using it as a cheap box cut summerweight bagstorm tent above timberline, you need to be able to control this air exchange.

B: I will also bring two ofhave used canvas wall tents and a sheet metal stove. These are the half inch thick closed cell foam padscat's meow for winter camping. The floor is always cold, but from knee height up, it's warm and DRY. Lines rigged near the peak turn clammy socks and mittens crisply dry by morning. No more beating the frozen boot to accept your foot in the morning. They don't lend themselves to human powered travel

(Historical note: During the Klondike Gold Rush, dog mushers would buy silk tents. Silk was about a third of the weight of canvas, and it was reasonable to pack a 20 pound silk wall tent, and sheetmetal stove made from a 5 gallon kerosene can. But they were well-to-do. The fare for a passenger riding out from Dawson was $600)

 

If I am in an area that permits it I will cut a bunch of spruce branches, or dogwood or alder twigs and make a pad about 3 inches thick to put my foamies on. This both makes the foamies better insulators, but also acts as a sink for snow on me, my footwear etc, so I don't lie on it and melt it. If the twig bed can compress some, the foam pad molds to you better, and the breeze has less access to that space between sleeping bag and pad.

The usual limit in winter camping is how good your sleeping pad is. If I'm anticipating really cold temps, I will bring two sleeping bags, one sized to fit over the other -- the outer often just a cheap box cut summerweight bag. I will also bring two of the half inch thick closed cell foam pads. Most of the condensation happens on the inner surface and inside the outer bag. In the morning strip the outer bag off, and stuff the inner bag quickly to try to expel most of the warm wet air as before it can condense. Compress the outer bag too, but before packing it, shake as much frost off of it as possible.

Insulation underneath is important. I have a knee length heavy duty parka that I used on dog sled expeditions. It was made from nylon pack cloth, with a heavy weight wool blanket cloth lining, and wolf fur rimmed hood. I would use it on top of my foam pad under my sleeping bag. That gave me an extra bit of insulation there. If there was a breeze running at night, I would sleep on one edge of it, and arrange the rest to block the wind.


 

The usual limit in winter camping is how good your sleeping pad is. If I'm anticipating really cold temps, I will bring two sleeping bags, one sized to fit over the other -- often just a cheap box cut summerweight bag. I will also bring two of the half inch thick closed cell foam pads.

If I am in an area that permits it I will cut a bunch of spruce branches, or dogwood or alder twigs and make a pad about 3 inches thick to put my foamies on. This both makes the foamies better insulators, but also acts as a sink for snow on me, my footwear etc, so I don't lie on it and melt it.

You sweat about a litre at night. You exhale something close to that. That moisture has to go somewhere, and at below zero temps, air doesn't hold much of it. You wake up with frost lining the tent, and your sleeping bag full of water vapour saturated air, likely with some amount condensed as frost on the inside of your sleeping bag.

You can make a case for a tent:

A: It's constructed with vents near the top and bottom so that it can act as a chimney. It needs to do several air changes an hour to keep up with the moisture release of the occupants. In this case it's likely no warmer than outside. If you are using it as a storm tent above timberline, you need to be able to control this air exchange.

B: I have used canvas wall tents and a sheet metal stove. These are the cat's meow for winter camping. The floor is always cold, but from knee height up, it's warm and DRY. Lines rigged near the peak turn clammy socks and mittens crisply dry by morning. No more beating the frozen boot to accept your foot in the morning. They don't lend themselves to human powered travel

(Historical note: During the Klondike Gold Rush, dog mushers would buy silk tents. Silk was about a third of the weight of canvas, and it was reasonable to pack a 20 pound silk wall tent, and sheetmetal stove made from a 5 gallon kerosene can. But they were well-to-do. The fare for a passenger riding out from Dawson was $600)

 

If I am in an area that permits it I will cut a bunch of spruce branches, or dogwood or alder twigs and make a pad about 3 inches thick to put my foamies on. This both makes the foamies better insulators, but also acts as a sink for snow on me, my footwear etc, so I don't lie on it and melt it. If the twig bed can compress some, the foam pad molds to you better, and the breeze has less access to that space between sleeping bag and pad.

The usual limit in winter camping is how good your sleeping pad is. If I'm anticipating really cold temps, I will bring two sleeping bags, one sized to fit over the other -- the outer often just a cheap box cut summerweight bag. I will also bring two of the half inch thick closed cell foam pads. Most of the condensation happens on the inner surface and inside the outer bag. In the morning strip the outer bag off, and stuff the inner bag quickly to try to expel most of the warm wet air as before it can condense. Compress the outer bag too, but before packing it, shake as much frost off of it as possible.

Insulation underneath is important. I have a knee length heavy duty parka that I used on dog sled expeditions. It was made from nylon pack cloth, with a heavy weight wool blanket cloth lining, and wolf fur rimmed hood. I would use it on top of my foam pad under my sleeping bag. That gave me an extra bit of insulation there. If there was a breeze running at night, I would sleep on one edge of it, and arrange the rest to block the wind.

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I'm taking a different tack. I have slept both in and out of a tent on many winter nights, and I will not use a tent unless there is significant wind or precipitation.

Here's the problem: The tent will keep most of the air from moving, but that air loads up with moisture from your sweat, your breath, and any damp clothing that came in with you. The net result is that you are now insulated with moisture laden air, which doesn't work nearly as well.


The usual limit in winter camping is how good your sleeping pad is. If I'm anticipating really cold temps, I will bring two sleeping bags, one sized to fit over the other -- often just a cheap box cut summerweight bag. I will also bring two of the half inch thick closed cell foam pads.

If I am in an area that permits it I will cut a bunch of spruce branches, or dogwood or alder twigs and make a pad about 3 inches thick to put my foamies on. This both makes the foamies better insulators, but also acts as a sink for snow on me, my footwear etc, so I don't lie on it and melt it.

If there are light breezes I will set up a tarp to block the wind. Preferred location is 45 degrees off the wind, facing the fire. This is the sweet spot for minimum smoke, and maximum wind protection. Heavier winds mean I'm away from the fire, under a spruce tree, with the tarp set to minimize wind speed. This will mean I have more condensation in my bags in the morning, and a less comfortable night. Ditto precip.

But most nights I just set up by the fire. I cut enough wood to keep the fire going all night. this way my nose stays warm and I don't get my bag soggy from condensation.