A quinzee is a snow shelter built by hollowing out a large pile of snow. Other types of snow shelters good for sleeping in include igloos, constructed by stacking blocks of snow that have been formed or cut; and snow caves, which are dug into a deep snowpack, ideally on a slope.

Snow caves are efficient for backcountry travel because they are fast to build, though not roomy. Igloos can be as big as you’d like but are a major undertaking. Quinzees can be built with less sensitivity to snow conditions than an igloo, since piling snow causes it to melt & refreeze to itself.

The major labor component of a quinzee is hollowing out the pile of snow through a small opening. What if you only had to pile up the snow that you wanted to be there as the walls and roof of your structure? This instructable will show you how to do that using a weather balloon. I found that you can build a quinzee tall enough to stand in and wide enough to sleep 3 people with about 2 hours’ work by 2 people.

Step 1: Equipment

Here’s the equipment you need.

-1 avalanche shovel per person

-2 avalanche probes (or 1 per person)

-2 200g weather balloons, $20 from High Altitude Science (you only need one, but take a spare!)

-1 foot bellows pump, e.g. $9 from Intex

-1 tent rainfly or tarp (will double as moisture barrier you sleep on)

-Snow stakes or other anchors for rainfly

-2 short & fat rubber bands

Variations and Notes:

You can use anything you want as a pump. The Intex pump I used is quite heavy at 2lbs, but only cost $9 and pumps a lot of air quick. I also tried an Exped Schnozzle Pumpbag (~$35), but it’s slower and it’s very annoying to have to use your arms to pump (will take around 300 bag-fuls). Finally, there are smaller foot bellows pumps that are also more expensive, which may be a good compromise if you’re actually planning to pack stuff in some distance from civilization.

Step 2: Start Pumping

Now to build it! Pick an open spot with clean snow, where it will be easy to transport (shovel) snow from a wide area. The moment you’ve picked your spot, plug your pump into the weather balloon nozzle, use a rubber band to make a decent seal, and start pumping – this will be your rate-limiting process.

For a 3-person quinzee, I’d aim for 5-6 foot diameter or 2 meters on your avalanche probe. An easy rule of thumb is that you’re done inflating the balloon when you can’t see the top of your friend’s head on the other side of it.

Step 3: Dig a Spherical Pit

While the balloon is being inflated, the rest of the team should start digging a spherical “nest” in the snow that the balloon will fit into. It’s a good idea to keep the surfaces flat as you’re finishing this up, because pointy bits will be poking the balloon. Toss the snow just outside the hole, because this snow will become your quinzee walls.

Tip: you can use 2 avalanche probes and a rubber band to make a gage, a bit like a compass from geometry class, to see exactly where you need to remove snow to make a spherical hole. Stick one probe deep into the snow, and pick an offset (say 50cm) between the probe tip and the bottom of your hole. Then put the rubber band 1 balloon radius (say 100cm) above that, or at 150cm. Now you can hold the second probe so its 100cm mark is at the fixed probe’s 150cm mark, and the excavated hole surface should be just touching it!

A note on hole depth: Practically speaking, you may as well dig out the hole for as long as takes to inflate the balloon, up to half-burying the balloon (maximum of one radius deep).

Step 4: Balloon in the Hole!

Once the balloon is inflated, drop it in the hole, orienting the nozzle and the hose to your pump at a spot where you want your entry tunnel to be.

Then, cover the balloon with the tarp or rainfly, and anchor the cover into the snow, as close to the sides of the balloon as possible since you’ll have to dig them out of the walls later. Tip: make sure you actually tie into your anchors, so they don’t pull free and get lost in deep snow later!

If you want, you can give it a few more pumps after it’s tied down, to get it locked into the cover more stiffly. It’s okay if the nozzle or your pump itself is leaking a little; there is so much air in the balloon that it’s not going to matter.

Step 5: Bury the Balloon

Now bury the balloon in snow! As you build up snow around the sides, the balloon gets squeezed up into the remaining hole. You may want to carefully place some chunks of snow on the very top of the balloon, so that it stays in more of a dome shape and less of a cone. Focus on carefully stacking snow to cover the entire balloon, minimizing the force of snow leaning against the balloon.

Once you have a covering layer over the whole balloon, pat it down with your shovel. If you pat forcefully, you may knock a chunk loose and push it into the balloon. That’s okay, add more snow to patch it up, and don’t pat quite so hard. Fill in thin spots you find. Your goal is to have 9-12” (25-30cm) thick snow everywhere.

Once you’ve done this, stop and take a well-deserved snack & water break of at least 15 minutes. This gives the snow time to re-freeze to itself, becoming a solid structure.

Step 6: Dig In

Now, dig out your pump, and disconnect it from the tube so air can start escaping. Follow the tube to the balloon nozzle. Dig with your hands as you get close so you don’t stab the balloon with a shovel. Carefully widen the hole, and then pull the tube out of the balloon nozzle so air can escape faster. Once your hole is wide enough, you can crawl in and squeeze the balloon so it empties faster. Now you’re ready to customize your quinzee! Smooth out the ceiling & walls to avoid condensation drips. It’s okay to push on the snow to pack it a bit from the inside. You can also dig or compress your floor, level out a sleeping platform, and widen out your entrance tunnel and stairs as you like.

Note that it’s often recommended to make the ceiling of your entrance tunnel lower than the sleeping platform, in order to reduce convective heat loss while you sleep. That means digging a fairly deep entrance tunnel if you’re not on a slope; you can also use an extra therm-a-rest or other items to block off the entrance tunnel when you turn in for the day. Enjoy!

Step 7: FAQ

Q: How should I build up snow around the balloon?

A: As evenly as possible, since it will balloon out in uncovered places. Also, consider carefully placing a few chunks of snow right on the top of the balloon, so it doesn’t balloon straight up as much while you’re stacking the walls.

Q: How thick should the wall be? If I can see light through it, is it too thin?

A: Thick enough that while building, a firm shovel pat doesn’t cause it to give in. If you can see light, that’s fine – and surprisingly thick snow still lets light through. Our test quinzee came out to around 30cm. What you should worry about is anyplace the slope of your base pile intersects a more dome-shaped covering of snow over the balloon. This is a weak point and you should add snow to smooth it out – this is what flying buttresses (https://en.wikipedia.org/wiki/Flying_buttress) are used for to stabilize architectural arches.

Step 8: Endnotes

This idea came about after I went quinzee camping (constructed the traditional way), had a blast, and obsessed over the following thought during the 3-hour car ride back home: how could one of these be built to minimize the amount of snow shoveling that has to be done? Key to this question is noticing that when removing snow from inside a cave through a small opening, one shovelful of snow has to be shoveled 3-4 times to get it outside and away from blocking the opening.

Initially, I thought a bunch about ways to use a displacement form to build around, and did some math to estimate how strong it would have to be. A tent-like structure crossed my mind, but a back-of-the-envelope calculation suggests the roof of a snow shelter can weigh in the ballpark of 1000 pounds. An inflatable structure was a natural next direction to look at, because they have the awesome property that you don’t have to worry about the total weight load, just the load per unit area. Just like your bike tire safely confines a fragile tube that can then be inflated to 100+ psi, I figured that a minimal inflatable structure could easily support a snow shell. Importantly, even that 1000 pounds of snow in the roof translates to less than 1 pound per square inch, so the inflatable form wouldn’t have to be inflated much at all beyond its own displaced volume.

I thought about different things that could serve as the inflatable form. Hammock maker Eno discontinued its camping couch; there’s another instructable that uses trash bags but I didn’t like the 1-time use aspect (was thrilled to see this proof of the general concept, though!); my friend Bailey said why don’t you just use a weather balloon? So I did! (Side note, a box of 20 33-gal Hefty bags weighs much more than a 200g or 350g weather balloon, and together could displace only a fraction of the volume. They may weigh less than the foot pump I used, though.)

The interesting math problem in building a quinzee this way is how deep to dig a pit for the balloon, such that the amount of snow required to build the walls, and that must be shoveled back out the opening, is minimized? This simplified problem collides with a practical problem (too complex to easily model): as snow is stacked against the side of a balloon, it’s squeezed inward and upward. Digging a hole (whose walls aren’t leaning on the balloon) and restraining the balloon with a top cover help mitigate this.

I initially modeled the shape of the quinzee as concentric spheres. But after building another one, I realized a big mistake here: if you’ve taken an avalanche safety class, you may recall that 45 degrees is about the steepest slope that loose snow will hold. So that means unless you pack it like crazy, you can’t have steeper than a 45 degree slope on an outer quinzee wall. Therefore, a quinzee is better thought of as a cone shape, with the interior being somewhere between a cone and a hemisphere. What this means, for minimizing snow shoveling, is that the walls get really thick towards the base as you increase roof height, so you’re going to want to dig that initial pit really deep.

How deep? I stopped doing math, but the question would be when is the buried portion of a spherical balloon equal in volume to a donut of snow around your hole that’s piled with a 45-degree slope? I imagine the answer is more than half the balloon’s volume, at which point it’s worth noticing that you’re shoveling snow up and out of a pit that is deeper than the height your snow fort will be above the surface. So that’s probably a good place to stop digging - no deeper than half-burying the balloon.

Thanks:

Rob for organizing the traditional quinzee camping trip

Rachael for being a sounding board and home weather balloon testing

Bailey for the weather balloon idea

Darci for advice on weather balloons

Justin for suggesting & loaning Mountaineering: The Freedom of the Hills as a reference on building snow shelters

Robert for helping build mini test quinzee

Scott for helping build the full test quinzee