How can people have fires inside igloos without them melting through the ice?



Edit: Thanks for the awards! First time i’ve ever received any at all!

In: Chemistry

What happens is the rough inside later of the igloo melts a little bit at first but the super cold ice behind it which is being kept cold by the outside temperatures freezes it again in to a smooth crust. Because there’s now less surface area the warm inside air is less effective at melting the surrounding ice.

So basically it’s a constant battle between the fire inside warming up the air and the ice and cold air keeping the structure frozen, and the achieve a balance at some point.

Snow with an ice layer over it is very insulative. That keeps the heat inside and the cold out. It also keeps the heat out of the actual snow and the ice sort of keeps itself cool. It is the same reason that snow that has a crust of ice takes so long to melt even if it is way above freezing.

Igloos often have a small hole in the side and one on top. The side hole allows fresh air while the top hole allows CO and smoke to leave. Much of the heat also leaves through that hole.

I learned how hard it is to melt snow/ice with fire in an interesting way. My boss told me to we had a “parade” of higher ups coming through. There was a bunch of dirty snow in the parking lot. I went to Home Depot and rented the biggest kerosene heater I could. Had guys pack it up high and pointed it right at the base. Maybe an hour later very little progress.

One of the guys who reported up through me walked by, called me a dumb fuck and said that’s going to take forever. It was 60 degrees out and he grabbed 2 guys and they broke it up and threw it in a thin layer over the parking lot. Took like 2 hours to melt on its own after that. It would have taken us a day to melt it all.

Anyway, getting schooled by a technician was fun. Little did he know I just wanted to play with a kerosene heater. But, he did get to call me dumb which was a positive for him and taught me a lesson on how many BTU’s it takes to phase change ice to water.,and%20it%20won't%20melt.

To avoid melting the ice, people must keep the ice below its melting temperature. That means that they can’t add heat to ice indefinitely. But while a central fire will always deliver some heat to the ice of the igloo, the ice of the igloo will also tend to lose heat to colder air outside.

As long as the ice loses heat at least as fast as the fire delivers heat to it, the ice won’t become any warmer and it won’t melt. Water has a lot of latent heat. This means that it requires a lot of energy to transform water from ice to liquid, even though the temperature stays at 0°C.

Furthermore, water has a high specific heat capacity, which means it takes a lot of energy to change the temperature at all. And finally, even though the air inside is maybe ~10°C, the outside might be waaay below 0°C, and might might be windy, causing the equilibrium temperature of the ice to be well below 0.

They say if you ever get stuck in a car in the middle of winter, a tealight candle on the dashboard can provide enough heat to get you through the night.

Not an igloo expert, but am firefighter trainee.

Fire science is… wild. The stuff you learn in high school chemistry doesn’t hold a candle(eyyy) to the real thing.

Heat wants to rise and so does fire. You know how they always say close doors and windows to contain a structure fire, and how modern buildings have actual fire doors? Basically what this does is contain a fire until help arrives. It’s not going to put it out.

What firefighters do in a fully involved fire is the exact opposite. They vent the roof directly above the hottest part of the blaze. This causes both smoke and heat to escape vertically so that a fire attack team can enter from the side and extinguish the fire without being melted. Turnout gear and water vapor alone have their limits.

In addition, water doesn’t magically extinguish fire, as you can see from oil fires burning on water. Water only cools the fire’s fuel below its ignition point and thus puts it out.

So I’d imagine with the igloo scenario, enough heat escapes vertically that the interior is warmed without melting the ice, and the cooling effect of the outside air on the ice keeps it in a solid state. I’m sure many igloos have melted from too much fire and too small a chimney.

I also always wondered how they are ventilated?

It looks like your question was mostly answered. I would add that another good example is that ice fisherman who are out on the ice for the day (not in a fishing shanty) sometimes start a fire on the ice for warming up and cooking. The ice melts a little and then a layer of cold water battles with the fire on one side and the ice on the other (very similar to the layer inside the igloo). Even after a full day of fire, it will only melt a few inches into the ice.

An important note is that the goal of warming the inside of the igloo is NOT to keep the inside a temperature that you would be comfortable in your home. It is to make it more comfortable in clothes and blankets. The structure does melt if the internal temperatures get too high. As others have said, you want to find an equilibrium so that the melting is not happening faster than refreezing. If you want the structure to last more than a few days, the internal temperature needs to be fairly low, say 40s or perhaps up to 50s. This is a welcomed respite from negative temperatures in the arctic.

Snow melt, humidity from your body, and breath will freeze into the cracks, helping to seal the structure and block wind and the elements from infiltrating. However, ice is a much worse insulator than the packed snow initially used to create the igloo, so you don’t want the walls to too thick with ice. The ice also helps trap moisture inside, thus increasing the relative humidity inside of the igloo. Super cold air is very dry, and can make it painful to even breathe. Humid air also holds heat better than dry, so a small heat source can provide a better warming effect when the humidity is slightly higher.

It is a lot harder to melt ice than most people realize. It’s not just heating ice from 0C to 1C; you have to add enough heat to cause a state change, which doesn’t even change the temperature. You are basically melting 0C ice into 0C water. Which also means that the melted ice doesn’t help you melt more ice.

[Here is a documentary that explains it better than I could.](

I’m an Inuk from Nunavut and I have experience with this! In the colder seasons of winter often between November to April are the peak freezing temperatures, the snow packs harder from winds and cold making snow easier to pack and build into shape, forming a stronger integrity of an igloo (proper name is ᐃᒡᓗᕕᒐᖅ “Igluvigaq” ) with the cold atmosphere keeps the exterior of the Igluvigaq frozen, the interior warms by the flames of stone lamp called ᖁᓪᓕᖅ “qulliq” melts a thin wall making film of ice. The ice is kept frozen by the outside, making the Igluvigaq insulated and keeping the Igluvigaq nice and toasty! Igluvigaq are often used in temporary shelter when going out to hunt and harvest away from family camps.

I have a follow up question about this:

How come mountaineers never seem to build igloos (ᐃᒡᓗᕕᒐᖅ as /u/IpodAndMp3 stated) when they get in trouble on a mountain?

For instance, in the 1996 Everest disaster, where 12 people died, not one had tried to shelter in the snow (as far as I know). In addition to that, I have never hear of *any* mountaineer trying to shelter in an igloo to combat exposure – which seems obvious for a number of reasons: snow is abundant and a professional camp stove is very light, compact, and can be used to make water from ice – I would assume that would be an essential thing on the way to the summit.

Now, I realize the Everest disaster has many, many, other factors: HACE, massive storm / wind, well above the death zone, lack of O2, fatigue (especially), etc. I am not trying to suggest I know shit about anything in this regard – it’s the one example I can think of. I am legit curious and as, like I said, I haven’t heard of this type of shelter in any / many exposure incidents.

My best guess is that snow on the tips of mountains are not “sticky” enough for this sort of endeavor?

Anyways, enlighten me.

Conduction vs convection. The convective heat put off by the fire just isn’t enough to overcome the amount of heat that the thick walls of an igloo can absorb through conduction. It would take an immense amount of BTUs to melt the walls of an igloo. Ever seen the video of the guy trying to melt the snow on his driveway with a flamethrower? It didn’t work very well…. It takes only a small amount of convective heat and few BTUs to warm the air inside the igloo. Think about breathing on the palm of your hand. The surface of your hand gets warm for about 3 seconds. But you could never breathe on the palm of your hand enough to make the back of your hand warm. Now imaging the back of your hand is -10 degrees. Your hand is going to be frozen regardless of a little warm air hitting one side of it.