Igloo mythbusting...

[hikingfish]

I was approximating volume as surface area (of, say, the outside) * thickness, which works for a straight wall or a thin enough shell.

Using your more precise formula for wall volume (what you called "total volume"; a math teacher would call it "shell volume"):

wall volume = 2/3*pi*(r+t)^3 - 2/3*pi*r^3
where r is the inner radius and t is the wall thickness
= 2/3 * Pi * ( r^3 + 3*r^2*t + 3*r*t^2 + t^3) - 2/3 * pi * r^3
= 2*pi*r^2t + 2*pi*r*t^2 + 2/3(pi * t^3)

Now compare that to the volume available in the cylinder under the inner radius r, if the snow depth is d:
available snow = pi * r^2 * d

As before, set available snow equal to wall volume. Also, out of laziness, write "p" for pi:

2p(r^2)t + 2prt^2 + (2/3)pt^3 = p(r^2)d

Cancelling is not as easy (I shouldn't have multiplied out, above), but we can get to:

2(r^2)t + 2rt^2 + (2/3)t^3 = (r^2)d

or
d = 2t + (2rt^2)/(r^2) + (2t^3)/(3r^2)

which, as I said, means d should be a bit more than 2t. How much more?

In any real-world igloo, we know that r is going to be, conservatively, at least ten times as big as t. (Example, nine-foot igloo, half-foot-thick walls, r is 18 times t.) Let's see what happens if we replace "r" with "10*t".

d = 2t + 2(10t)(t^2)/((10t)^2) + (2t^3)/(3(10t)^2)
= 2t + (20t^3)/(100t^2) + (2t^3)/300t^2
= 2t + (1/50)t + (1/150)t.

d = 2.026667 * t

In other words, the extra terms are pretty negligible; 2t was darn close. The bigger r is compared to t, the more negligible the extra terms are.

Wow! Very cool proof. It appears I was out-math'ed hehehe (not that it's hard to do lol). Sorry if I had to do the calculations a different way, I didn't quite understand what you were saying I guess.

 

[hikingmaineac]

After learning this the hard way on a very stormy night at Edmands Col building a snow cave (taking turns digging),

Tim, I'm just curious - was building a snow cave in the col a planned event or last resort situation? Care to share the story (or a link to the previously written TR?)

Thanks!

Brandon

 

[hikingfish]

Tim, I'm just curious - was building a snow cave in the col a planned event or last resort situation? Care to share the story (or a link to the previously written TR?)

Thanks!

Brandon

I was also wondering the same thing. I was also wondering how steep was that slope where you built the cave?

Fish

 

[Dr. Dasypodidae]

Baffin Igloo Construction, April 1992

I will try to upload a couple of sequential shots if this one works.

View attachment 2486

 

[Dr. Dasypodidae]

Here are two more, with me in my old slime-green Dynamic b/c ski boots; uggghh.

 

[nartreb]

Wow! Very cool proof. It appears I was out-math'ed

Actually I made a really stupid mistake. I bet you built a nine-foot diameter igloo, not a nine-foot radius igloo. My "conservative" ratio of radius to thickness wasn't quite conservative enough. Your actual igloo would be very close to my "conservative" result, but for a truly conservative model, say r = 5 * t (corresponding to a 5-foot inside-diameter igloo with half-foot-thick walls, or ten-foot inside diameter igloo with foot-thick walls), the extra terms aren't quite so negligible:

d = 2t + 2(5t)(t^2)/((5t)^2) + (2t^3)/(3(5t)^2)
d = 2t + 10t^3/(25t^2) + 2t^3/(75t^2)
d = 2t + (10/25)t + (2/75)t
d = 2.42666667 * t

Throw in a 70% usability fudge factor, and we get:

d = 3.466667 * t

 

[hikingfish]

Here are two more, with me in my old slime-green Dynamic b/c ski boots; uggghh.

Those lime green boots are so retro

Seriously, very cool igloo pics (+rep). I'm wondering if you built it yourself or you had some help from a guide? Did you take the blocks from inside the igloo or you had a quarry nearby? And finally, how big were the blocks approx.?

 

[sardog1]

I'm not sure exactly what you mean in your second point. Of course it's more work, that's for sure, to stomp an area with your snowshoes/skis for 20 minutes and then wait for that area to sinter. But you can (and should!) take your time while stomping and afterwards building the igloo so you don't sweat. Exactly as one should do for any snow shelter. If you're building a snow shelter in wet snow, then that's another story. But then again, you probably should of brought a tent if conditions are so close to freezing point. Wouldn't you agree?

The tent is exactly the point for New England and similar climates (e.g., the western slopes of the Pacific NW and the Sierras.) Building a snowshelter during a trip across country in these locales will cost you time and energy better spent elsewhere. As Tim Seaver has noted, even digging a snow cave is often a wet affair. Quebec has colder temperatures and dryer snow in some parts, so snow shelters might make some sense up there at times.

Snow is a fabulous insulator under the right circumstances. If the temperature drops below -30 F for an extended period, you need either a snow shelter or a fire inside a tent, or you should be on Denali enjoying the view.

I've never been a quinzhee fan. Lots of work and perspiring for little reward, IMO. Similarly, if I'm lying in a snowtrench, it's from necessity, for just one night. Been there, done that.

 

[sardog1]

I was also wondering the same thing. I was also wondering how steep was that slope where you built the cave?

Fish

Snow caves require a substantial amount of snow on a fairly steep slope. One of the things to consider is the possibility of someone tramping around overhead. You generally want a couple feet or more of roof above you.

Another reason for finding a steep slope with enough snow is that throwing snow up out of a hole is very inefficient and gets more difficult as you progress with the excavation. You want to be able to tunnel into the hillside and avoid digging down as much as possible. That requires at least five-six feet of horizontal distance through the snow from you to the side of the hill. Most times when I did it with just five feet, I regretted it.

One more thing on snow caves. Some people are unsuited to being in a snow cave because of claustrophobia. Some of those people will try to talk themselves into it. But that's a prescription for a nasty escalation of the claustrophobia at the worst possible time. I've put a lot of people into snow caves in the course of training avalanche dogs. If they didn't tell me that they were really, truly enjoying it once they got in, I brought them out. Something to keep in mind if you're planning to use snow caves, or even igloos, for a trip.

 

[Dr. Dasypodidae]

Seriously, very cool igloo pics (+rep). I'm wondering if you built it yourself or you had some help from a guide? Did you take the blocks from inside the igloo or you had a quarry nearby? And finally, how big were the blocks approx.?

Great questions.

The architect was Joavie Alivaktuk, the shorter guy on the right in the first photo and the leading outfitter in Pangnirtung at the time (perhaps he still is). I hired Joavie to take us via snow machine (sicky-doo in Inuktitut) to some remote lakes for sediment coring (paleoclimatology research) and he wanted to show me and my field assistant Stephen, the 6' 4" tall guy on the left in the first shot, an example of traditional Inuit knowledge. So, judging from these two guys for scale, I am estimating that the blocks were about 2.5 ft x 2.0 ft x 0.5 ft in dimension? The final keystone block at the peak of the roof is smaller and the trickiest to carve and fit into place.

Stephen and I cut and transported the blocks with one snow saw, barely able to keep up with Joavie who shaped and fit our blocks into place with another snow saw. As you can see from the first photo, we excavated the floor of the igloo to harvest blocks for the first row of the spiral, with the remaining blocks coming from the exterior. The entry trench (see second photo) was then dug another couple feet deeper than the interior floor to keep the inside just below the freezing point (the outside air temperature was about 30 F below zero, as I recall). A couple of vent holes punched through the peak of the roof with a ski pole are also required. Joavie apologized for not having access to river or lake ice at our location, which he would have used to fabricate a window or two.

The whole process took us less than 30 minutes, which Joavie told us was pretty good time (my guess is that we did not set any records). We waited for another 30 minutes or so for the snow chinks between the blocks to metamorphose before standing on top (see last photo; a little ritual, I think, if one is not desperately in a rush to escape the weather). Very little sweat equity in igloos, but probably not safe from polar bears, if you remember Gary Larson's Far Side cartoon where one P bear says to the other: "I just love these these things, crunchy on the outside, chewy in the middle."

Unfortunately, we rarely get the perfect snow for igloo building in the Northeast, such as found on Baffin, or in Antarctica, where I have also built igloos. The igloos on Baffin and in Antarctica will stay standing for weeks in cloudy or dark conditions, but sag pretty quickly in other places such as western Canada, where we built an igloo in the Selkirks that was uninhabitable after just three nights (we had to build a second, but perhaps we only needed Joavie there to show us the way?).

 

[Tim Seaver]

Tim, I'm just curious - was building a snow cave in the col a planned event or last resort situation?

Those pics are from 1992, on a 4 day Presi Traverse. The snow cave was indeed planned, although we had a tent with us. Dingmaul Rock is the steep slab of rock jutting into the sky in the top pic, which is just before where you would cross the steep open snowslope ascending from Edmands Col headed south on the Gulfside (north of the Jefferson Summit Loop Junction).

Snow blasting across the ridge over this sharp edged rock fills in this lee pocket pretty regularly. We made the cave about 50 feet above the trail. The slope above the cave entrance is probably 60 degrees or so, but fairly short. Because so much spindrift is constantly falling down this slope, we needed to clear our vent holes pretty regularly, as even our pretty big doorway was snowed in in no time. Make sure to bring a shovel inside and keep it near your pillow

 

[hikingmaineac]

Those pics are from 1992, on a 4 day Presi Traverse. The snow cave was indeed planned, although we had a tent with us.

Thanks for the info!

 

[Little Rickie]

The whole process took us less than 30 minutes, which Joavie told us was pretty good time (my guess is that we did not set any records). .

I'm impressed.

 

[nazdarovye]

I did a trip a year ago in Yellowstone with a group of fellow writers from Backpackinglight, and we brought along the Grandshelters "Icebox" igloo tool with plans to build igloos at each of three multi-night camps.

http://www.grandshelters.com/

Even with the help of the tool - which did result in a nice igloo - I thought it was an incredibly inefficient use of energy for this kind of trip to make the igloo. Temperatures got down to -14° or even a little colder - so from that standpoint the igloo was pleasant, with the temperature getting no lower than the teens inside - but it took hours to make.

I was the sole person to sleep in a tent (a Hilleberg Jannu) and I was so much happier in it. It took just minutes to set up, it protected me from the wind, and I could hear nature all around me (animals, falling snow, wind in the trees) versus the dead silence of the inside of the igloo.

The group scaled back plans after that, and moved on to another site where they built two igloos and decided not to move after that, just doing day skiing around the second location.

Here's my tent, with the igloo (10' diameter) somewhat visible in the background:

Here we are starting to break down the igloo (it was near a fairly popular trail, and the rangers told us to destroy it to keep the curious out):

And here's more of the group standing on its roof, which even after we'd chipped away at the sides, still easily supported their weight; I'll give igloos that: properly built, they're strong and durable.

Igloo Ed from Grandshelters, and Will Rietveld, one of the writers (with the shovel in the pictures), build igloos early in the season in Colorado and use them all winter, returning multiple times. For that kind of use, they actually make a lot of sense.

 

[RoySwkr]

Joavie apologized for not having access to river or lake ice at our location, which he would have used to fabricate a window or two.

He did that in "Nanook of the North", I always wondered if that was for real or just the movie

 

[The Hikers]

Of course modern day Inuits ride on snowmobiles, have no knowledge of formulars, and don't sweat.

 

[DougPaul]

Of course modern day Inuits ride on snowmobiles, have no knowledge of formulars, and don't sweat.

A few still run dogs, from what I have read.

Perhaps more interesting is their traditional clothing system: they use two layers. The inner layer is made of thin animal skin, sort of like a version of long underwear. The outer layer is made from heavy animal fur (caribou, IIRC) and seals well around the openings. Thermal control is by venting. This system is still superior to our multi-layer systems in some conditions.

When then enter an igloo, they take the outer layer off and leave it out in the cold. Otherwise the moisture in the garment would melt and freeze stiff next time they go out. (I had to connect it to igloos somehow... )

Doug

 

[Dr. Dasypodidae]

A few still run dogs, from what I have read.

Perhaps more interesting is their traditional clothing system: they use two layers. The inner layer is made of thin animal skin, sort of like a version of long underwear. The outer layer is made from heavy animal fur (caribou, IIRC) and seals well around the openings. Thermal control is by venting. This system is still superior to our multi-layer systems in some conditions.

When then enter an igloo, they take the outer layer off and leave it out in the cold. Otherwise the moisture in the garment would melt and freeze stiff next time they go out. (I had to connect it to igloos somehow... )

Doug

Yes, Inuit dog teams are coming back after a lengthy hiatus, but snow machines are still the primary overland transport means, in the eastern Canadian Arctic anyway.

When my feet were getting cold inside my plastic boots, Joavie noted (later while we were in the igloo ) that my VBL socks were the problem. So, as a scientist, I experimented the next day with a VBL sock in one boot and not in the other, and he was indeed correct. I think that the explanation perhaps was that we were working up just enough sweat in our work coring lake sediments to make thermal venting more effective for staying warm than the vapor barrier.

I have done the same as Inuit in leaving my goretex shell outside the tent when winter camping.

 

[Chip]

Keith in the Cave

Nothing to add to this excellent discussion except...this is a really cool picture ! Thanks Tim !

 

[pks4000]

Hail the Igloo

Again .....the Ice Box Igloo form from Grand Shelters makes building unsweaty and precise. And it works with snow textures that wont pack into a snowball like western powder and eastern granular . Weve built in both

The time it takes is about the same as to pack out a tent base, wait for it to settle, and bury snow stakes .
In the morning you sleep in, pack your stuff and hit the trail.

You dont have to dig out frozen snow bags, whack and defrost the tent and fly and ground cloth, roll it all up, jam it in the now smaller stuff sack and carry 1-2 lbs of frozen water vapor. All with 1- 2 hours of sleep