Submitted by SunCloud-777 t3_zy30z3 in todayilearned
I knew this, but I still don't understand why they don't melt over. If snow is a good insulator, and the inside is above 0ªC, then why doesn't it melt? I suspect the snow reaches a balance between the outside and the inside that keeps its integrity, but shouldn't igloos drip water from their ceiling?
There is also a famous "Ice Hotel" made completely from ice. I remember watching people walk around inside it fairly light dressed and yet there wasnt any water at all.
Overall, the exchange of heat from a couple of people or even a smaller cooking/warming fire to the ice will be about the same or less than the loss of heat from the ice to the outside air. The best way to ensure that this is the case is to have a decent sized but still small opening at the top of the igloo (avoiding the centre because it would collapse). This lets excess smoke and heat rise out the top instead of possibly accumulating and causing slush and drips while still allowing for enough radiating heat from the fire to keep you warmer.
also the inside ices up. This prevents any warm air from penetrating the snow layer.
yes, from what i understand, a small vent is situated at the top of the igloo, plus bec it’s dome-shaped what little ice melt will flow down the side.
When we're talking about being "warmer" inside it could still be below freezing. If it's negative 20C and windy outside having a space that's 0C with no wind will feel way warmer.
Thats a good point. I guess -1ºC would feel comfortable without wind and with winter clothes when its windy and -15ºC outside.
Can confirm. I’ve slept in a snow cave a few times and it’s quite comfortable inside without the wind chill.
I’ve slept in a snow cave a few times in the pacific NW. It does in fact start to melt the snow a little bit, and I recommend making your snow cave a smooth arch on the ceiling. If you leave any pointy bits on the ceiling the melt water can drip down them and onto your sleeping bag. If it’s smooth any water will run down the side and now get you wet. It’s not enough melt to cause problems though. Just enough to melt the rough snow on the surface.
Outside temps were always between -5 and -10, so it may be different in the arctic or even just the interior where it gets colder than the coast.
Snow caves overall are quite comfortable though. The temp hovers around freezing, but since the air is so still it’s comfortable to take your shirt off and get changed.
water is a poor conductor of heat, meaning you have to put a lot of energy (heat) against it to heat it up (or cool it down). So, ice "wants to stay ice".
this is why ice cubes work so well to keep drinks cool.
so, if you think about how easy it is to heat air up, and compare that to water... your igloo example starts to make a little more sense.
It's wrong to say that water (or ice) is a poor conductor of heat because it takes a lot of energy to melt it. It's correct to say that water has a very high "heat of fusion" (latent heat involved in turning 0-degree ice into 0-degree water). Conductance refers to its ability to carry heat from a hot object on one side of it to a cold object on the other side. Snow (not ice) has very low conductance due to its large air content, the same reason house insulation works well; it has nothing to do with ice's high heat of fusion.
> Conductance refers to its ability to carry heat from a hot object on one side of it to a cold object on the other side
edit:
> It’s wrong to say that water (or ice) is a poor conductor of heat because it takes a lot of energy to melt it.
not what i said.
you basically said i was wrong, and then explained something else, said in other words.
i was trying to keep it simple. sure, it's not 100%. what i said is basically right, i explained in way that's easy to understand. unlike your explanation.
warm air inside the igloo does not conduct heat very well through the igloo material. if water was a better heat conductor, it would melt faster. many of the different thermodynamic properties are related to each other.
The reason it takes a lot of heat to change the temperature of water, or to cause a phase change from solid to liquid, or from liquid to gas, isn't because "water is a poor conductor of heat," but rather because "water has a high specific heat," which is the amount of energy (calories, BTUs, etc) needed to change a given weight of the material (one gram) by a given amount (one degree celsius).
This is what makes water pretty much the "ideal material" to use to transmit power in things like steam engines (turbine steam engines are still heavily used in power generation) or to carry heat in things like engine cooling systems or residential/commercial heating systems.
Water really has quite a few remarkable properties from a scientific or engineering standpoint.
>... you have to put a lot of energy (heat) against it to heat it up (or cool it down)
This refers to specific heat (energy required to change temperature) and is not the same as thermal conductivity.
>Ice wants to stay ice. this is why ice cubes work so well to keep drinks cool.
This refers to heat of fusion. Also not the same as thermal conductivity.
You could replace the ice in snow with different substances with lower specific heat, lower heat of fusion, and a melting point so high that melting is irrelevant, and it would still be a poor heat conductor due to the large air content.
every one of your comments in your comment history is argumentative, about stupid details and generally telling other people they are wrong.
you seem like a genuine asshole.
edit: omg that creep actually replied from an alt account just to get the last word in! hahahahaha
and every one of your replies in this thread is you being an argumentative asshole who also happens to be wrong half the time.
You were wrong though.. you said it was a poor conductor of heat since it takes a lot to heat it up….
Those are different things.
Its heat conductance isn’t amazing, but is not the same or well related to its specific-heat-capacity & the energy it takes to phase change…
None of that has much to do with igloos keeping warm largely by being a windbreaker & containing the air in the space… it anything.. its the conductivity of the air in the space that matters… and not the walls at all.
Water is an excellent conductor of heat, that's why it's so often used as a coolant.
The term they meant to use is "Heat Capacity".
Water has a high heat capacity; it takes a relatively high amount of heat (energy) to cause a change in temperature.
This is also why it makes a good coolant, as it can then transfer that heat.
this is really really wrong
water is not a good heat conductor, look it up.
edit: here's a link link
> In terms of heat conductivity, water is classified as a poor thermal conductor and acts as an insulator by resisting the flow of heat through it.
wow, this goes to show how much upvotes actually mean
I don’t think there’s an agreed upon definition of “good” conductors.
In an engineering context it’s a mediocre conductor and can’t compare to most metals, but in a wilderness survival context water is a very good conductor of heat and is to be avoided at all costs if you want to stay warm.
In practice it’s a better conductor than snow, rock, and any other material you’ll find since it’s a liquid (I know that’s not technically correct, but in practice it might as well be).
> I don’t think there’s an agreed upon definition of “good” conductors.
heat conductivity is measurable, and predictable link
The unit of thermal conductivity, k = J/s⋅m⋅C°
there's a table listing some materials.
one of the really unusual characteristics of water is its low heat conductivity, which is a basis of its importance for life on earth... if water conducted heat more, it would freeze faster, potentially also from the bottom up, and global temperatures might swing too fast to support life. the same goes for ice and it's unique characteristics.
Yes there is an element of heat capacity and other thermodynamic terms going on... but i was keeping it simple for the person i was commenting to. if someone doesn't know why an igloo doesn't melt, it's easier to explain with terms they might know better.
You didn't address a single thing I said. I'm aware that it's measurable and I don't need the physics lesson. Besides, you're not in any position to be lecturing anyone on thermodynamics.
i did address where you were flat out wrong, and then provided a scientific example as to why you were wrong. that you dismissed it, says all i need to know about this discussion with you.
"Good" is a subjective measure. No one has defined a cutoff point between good and bad conductors. You did not address that at all. I said that "in an engineering context it’s a mediocre conductor" and you just provided numbers that support that conclusion.
In the context of wilderness survival, you can eliminate most materials on those lists and compare its conductivity to rocks, snow, trees, bushes, grass, air, etc. Suddenly water is a very good conductor relative to the other materials you are likely to encounter.
wow dude, you just don't give up, huh. you picked a fight and your first sentence was wrong and you're back tracking.
"oh... well 'good' is a subjective measure"...
i said it was a bad heat conductor, and you took the opposite stance, and now you're trying to qualify your answer with completely different scenarios.
seriously man, i don't want to talk to you. this discussion happened yessssssterrrrday. you are a day 2 reddit twat that reads over comments and nitpicks them to death. ain't nobody got time for that.
I said the same thing in two different ways since you didn't understand the first time. That is not back tracking. If you don't want to discuss it you can stop replying any time.
This is wrong in at least four different ways:
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