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Igloo building: blocks, sheets, triangles, volumes, areas and glue
Following on from preparation and initial mincing, the next things to decide on where how to create the chicken wire skeleton, and how the blocks would be attached to the substrate given the extra complication of a white sheet in between the two.
Chicken wire dome
Chicken wire will be great as a skeleton, as it's relatively easy to shape, but can still be nice and sturdy if you need it to be. The mesh structure will be really useful for anchoring it into the ground, and attaching the coverings, too. However, it only bends nicely around one axis at a time, as it barely compresses or expands as a sheet at all. That means making cylinders of chicken wire and expecting to be able to stack and bend them into a dome is not going to work.
What I'll do instead is to cut 16 equally sized isosceles triangles, chain the bases (b) together into a loop, then stitch neighboring long sides (l) together, eventually joining all the acute vertices at the top of the dome.
It's pretty likely this won't hold its own weight particularly well, so I may need a single vertical pole in the middle of the dome.
Attaching the blocks
The polystyrene blocks must be secure (because of the wind), quick to put on, and easy to take off. And as the polystyrene itself is awkward to work with, I'll do as much of the hard work as possible before leaving for Nevada. The best solution seems to be to attach the blocks onto strips of white fabric, measured to fit around the igloo in courses. These strips will be useful in keeping everything together during transport, and make it super easy to attach and detach the blocks once on the playa.
I wasn't sure about how to permanently bind polystyrene onto fabric; I wasn't sure until I found This to That. Hot glue!
As for attaching the fabric strips to the sheet and chicken wire underneath, I'm not sure. However, I do know that it's a much easier problem to solve than dealing with the blocks.
Next up: trying to make custom blocks of polystyrene, working out how much chicken wire I need, finding suppliers and finally the pre-build prep work!
Igloo building: preparation and initial mincing
Burning man is only 6 weeks away, and my highfalutin plans to build a polystyrene igloo on the playa are looking ambitious at best. So, fueled by some Arctic architecture brainstorming with my sister, this weekend I began making plans for how I can make this work.
Size
My first pass at sizing was that I'd like to be able to stand up in the centre of the dome (so 195cm inside radius), and that the walls should be around 20cm thick so that you get some real thermal insulation benefit during the hot day and cold night.
Unfortunately, this works out at being over 5 cubic metres of polystyrene. That's a lot, considering we need to fit it in the van to ship it in and back out, along with hundreds of litres of liquid nitrogen, bikes, water, people, a geodesic dome, etc..
Scaling this back to 180cm at the zenith, with 10cm thick walls, it comes out at 2.15 cubic metres of polystyrene, which is a lot more practical, although still pushing what we can realistically take.
Design
I got really inspired by this old 1940s Canadian public information film about traditional Inuit igloo building (video doesn't work in the UK, unfortunately...). I'd assumed igloos were built much like houses, with interlocking blocks going on top of others in courses. In fact, it turns out that the best construction method is to spiral upwards, round and round from bottom to top, so there's effectively only one course of blocks which loops round on top of itself. This means you never have that awkward first block in a course which would have nothing to butt up against. By spiralling up, you always have a block below and a block to the side to nestle up to (image from WikiMedia):
Using this method, one man can create a 6" high shelter in less than an hour, using nothing but the stuff he's standing on.
My initial thoughts were to mimic this proven design very closely, working out some way to bind blocks of polystyrene together that would be easy to detach at the end of the week, ready for shipping back to SF and reuse in the future.
However, after some thought, I think the traditional method just won't work for polystyrene. Firstly, the stuff is so light that it needs no encouragement to fly off at the merest hint of a breeze. Secondly, while snow blocks can be mushed up and mashed together, naturally binding together as they re-freeze, polystyrene just doesn't behave that way; each block would have to be manually, laboriously anchored to its neighbours. Thirdly, you can easily cut a doorway into a finished igloo, but cutting holes in the polystyrene would dramatically weaken the structure and produce loads of non-biodegradable, impossible to catch white beads flying everywhere in the wind.
So, the design I'm going for is a three stage process:
- a chicken wire skeleton to the desired internal size, complete with doorway, anchored into the dirt with rebar
- a white sheet over the chicken wire
- blocks of polystyrene attached individually to the chicken wire, with some reversible binding
The idea is that the wireframe will be free standing, and give us a substrate to build on. The sheet is to fill in the gaps between blocks, keep the wind out and complete the "all white" effect. If we manage to get the blocks nestled together closely enough, very little sunlight will make it through directly to the sheet.
What next?
- How best to create an igloo shape out of chicken wire? That stuff is pretty horrible to work, especially with 3D curves
- How to get / create polystyrene blocks? I'd like to make them myself if possible...
- How to attach the blocks to the chicken wire, through the sheet
- How big should the blocks be? Is it practical for them all to be the same size?
- How much will it cost?
