Is a snow cave always 32 degrees?

[adirobdack46r]

This could easily have been put in to the Mt Hood thread but it is a question all its own so I started a new thread. On CNN online I listened to an interview from a guy that was stranded on Mt Hood in I think 1976. He made a statement that caught my attention and wondered if anyone could confirm or deny it. He was talking about it being windy and cold on the surface but he said that once you dig in and build a snow cave "it is calm (no wind) and 32 degrees inside because that is the temperature of the snow" I know snow is an awesome insulator and the cave may warm up inside from body heat etc. but is it true that even if it is below zero outside that it will be no colder than 32 inside the cave? Doesn't seem possible that is why it caught my attention. I'm sure some of you out there have some great technical insight on this.

 

[JohnL]

Google "snow cave" + "inside temperature" and you'll find plenty of links to information on snowcaves and inside temperatures. Most of them say 32 degrees and some say 32 to 40 degrees.

JohnL

 

[Tom Rankin]

"it is calm (no wind) and 32 degrees inside because that is the temperature of the snow"

The snow is whatever temperature it is. Ice/water does not stay at 32 when it freezes. There could be other factors at work, but it is not the temperature of the snow.

 

[bikehikeskifish]

Snow by itself is not necessarily 32 degrees. If it were, we'd only need one temperature for ski wax. It does have a maximum temperature of 32 degrees (ignoring pressure and impurities, etc.)

However, snow is an excellent insulator, and just like sleeping bag loft, more means more insulation (it's all about dead air space.)

So, building a snow cave out of thick snow walls will insulate the contents. Which means, of course, that if it was 0 inside when you started, it will tend to stay 0. Unless of course you get in, in which case, much like your sleeping bag, you will warm up the inside. If it got too much above 32 inside, things would get mushy. The heat goes to melting the snow, rather then further increasing the air temperature.

from the depths of my memory of college physics

1 cal = heat required to increase the temp of 1g of water 1 degree Celsius.

80 cal = heat required to change 1g of ice at 0 degrees C to water at 0 degrees C, so it is hard to warm the cave too much above 32, as most of the heat would go to converting things to water, losing insulation along the way.

DougPaul--correct me if I'm wrong

It works for igloos, right?

Tim

 

[SAR-EMT40]

80 cal = heat required to change 1g of ice at 0 degrees C to water at 0 degrees C, so it is hard to warm the cave too much above 32, as most of the heat would go to converting things to water, losing insulation along the way.

Changing the air temp is different though. The inside air temp can be above freezing because it takes lots more cals to convert the ice inside from 32degree ice to 32 degree water. You have to keep pumping the heat into it for a period of time. The 80 cals you are talking about is called latent heat of fusion (melting).

Keith

 

[DougPaul]

Snow by itself is not necessarily 32 degrees. If it were, we'd only need one temperature for ski wax. It does have a maximum temperature of 32 degrees (ignoring pressure and impurities, etc.)

Snow at 32F can have a wide range of water contents, which certainly can affect ski waxes along with snow temps.

However, snow is an excellent insulator, and just like sleeping bag loft, more means more insulation (it's all about dead air space.)

Dry fluffy snow is a good insulator as long as the inside and outside are both below 32F. As the snow gets denser and/or wetter, its insulation quality goes down.

So, building a snow cave out of thick snow walls will insulate the contents. Which means, of course, that if it was 0 inside when you started, it will tend to stay 0. Unless of course you get in, in which case, much like your sleeping bag, you will warm up the inside. If it got too much above 32 inside, things would get mushy. The heat goes to melting the snow, rather then further increasing the air temperature.

from the depths of my memory of college physics

1 cal = heat required to increase the temp of 1g of water 1 degree Celsius.

80 cal = heat required to change 1g of ice at 0 degrees C to water at 0 degrees C, so it is hard to warm the cave too much above 32, as most of the heat would go to converting things to water, losing insulation along the way.

DougPaul--correct me if I'm wrong

Looks ok to me.

Except there is another factor:

Your exhaled and perspired mosture and water vapor from your stove and cooking mostly condense in the walls. The condensing moisture releases about 540 cal of heat per gram of water into the walls. The combination of condensed water and the heat melted snow increase the drips and speed the metmorphosis into denser and less insulating snow. One reason that one might have to move to a new cave every now and then.

It works for igloos, right?

Igloos are just a form of man-made snow cave.

The air inside a snow cave is not a perfect conductor, so the air close to your body can be a bit warmer than the walls, resulting in reports that the temp inside can be ~40F. The Inuit used to put a fur liner in their igloos, so it could be even warmer inside--warm enough that they used to sit around bare-chested.

Note that igloos and snow caves last longer at lower temps. The warmer it is outside, the faster the melting and metamorphosis. (It may be desirable to shave some snow from the outside of an igloo to keep the snow in the wall colder if it gets too warm outside.) Eventually the roof will sag and you will have to move.

Doug

 

[bcskier]

According to Danielsen

I have a 1972 copy of John Danielsen's Winter Hiking and Climbing, ADK in which he gives a table on Relative Warmth Provided by a Snow Shelter referenced to Innes-Taylor, Alan (ed.), Arctic Survival Guide, Scandinavian Airlines System, NY, 1957. To wit here is what it says:

With outside temps ranging from -55 to -2 F, temps inside a snow shelter ranged from 7 to 23.5 F. The highest of these (23.5) and the biggest differential was in a situation where there were 2 occupants and 2 candles for 15 minutes with the outside temp being -48 F. The second was measured in the morning after two occupants spent an overnight in the shelter and with no additional heat provided. The internal temp was 19 F and the outside temp was -55 F.

From personal experience the temp. in a snow cave can be well above freezing especially when you have numerous candles for light sources and a stove going. Of course you need to have some airflow to guard against CO build up but it is usually comfortable enough to work without gloves on even when there are absolutely atrocious conditions going on only a foot or two away from your head.

bcskier

 

[TomD]

I recently saw a story on tv about a guy who was dogsledding in the Arctic. He and his guide (an Eskimo) and their dog team got caught in a bad storm and rode it out in an Igloo they built. I think he said it was -65F outside and about -20F in the Igloo. It may have been colder inside. The dogs were fine because they were buried in the snow and that kept them warm enough. Hard to believe.

 

[DougPaul]

The dogs were fine because they were buried in the snow and that kept them warm enough. Hard to believe.

From what I have read, that is standard operating procedure. The dogs' fur evidently has provides enough insulation that the snow stays below freezing and they stay nice and dry. The more snow that piles on them, the warmer.

A number of animals burrow into the snow to escape the cold. The risk is a bit of rain followed by a drop in temps imprisoning them under a layer of ice.

I have had grouse explode out of apparanently undisturbed snow as I skied by. A bit of a surprise...

Doug

 

[Nessmuk]

From personal experience the temp. in a snow cave can be well above freezing especially when you have numerous candles for light sources and a stove going.

I've built and slept in numerous snow shelters (quinzees). A few when winter camping, more often I get my practice training Boy Scouts in cold weather camping skills. One particularly memorable weekend the temperature never got above zero during the day and dipped to -35 at night. With just me and 2 small candles the temperature inside stayed around +30. In the morning (candles out) the temperature was at 24. 30 is quite comfortable, the absolutely still air makes it feel even warmer. Any warmer than that and it feels too wet, everything that touches the walls gets wet, the roof sags after a day.

I plan on an hour to pile up the snow, another hour to let it settle before digging (to give the snow crystals a chance to naturally interlock for strength), yet another hour to dig out the shelter. The digging is a wet job, best done wearing a rain suit over otherwise light clothing to avoid sweating too much.

 

[Maddy]

The dogs were fine because they were buried in the snow and that kept them warm enough. Hard to believe.

A good solid dog is an amazing thing to watch in the bitter cold. I have observed mine lying on mounds of ice and snow in my own yard and never flinch. When I did my OB course I saw the forest service sled dogs. They were out with no shelter and none the worse for wear. I'm sure they bring them in if the are sick or injured but they sure do seem to enjoy the frigid cold. Sure wish I have their fur coats!