The Shipping Density Problem[edit | edit source]
Hexayurts are light, but they are not small. An 8' unit (160 square feet) takes 12 4' x 8' sheets, or a package four feet by eight feet by one foot. A 40 foot sea container will only fit 80 units, and that's just not nearly enough.
There is an answer: ship the buildings without the air which provides both strength and insulation, and expand the dense shipping form into buildings at the disaster site / war zone.
It involves developing some new technology, but it is clearly within the scope of the possible, and possibly even the easy, at least in one case.
Materials Options[edit | edit source]
There are two promising construction materials we have worked with.
The first is modified polystyrene coated with aluminium foil (commonly used in the construction industry for insulating houses - go to any Home Depot and ask for Tuff R by Dow.) That's what most of the units I've made were built from.
The other is hexacomb cardboard, used universally in the packaging industry. Hexacomb cardboard looks like an inch thick honeycomb, with the faces covered with nice thick craft paper. In a hexayurt context, a foil facer would be added for waterproofing, and there are a lot of options with this material for additional waterproofing and strengthening treatments.
Hexacomb Cardboard from Pregis - These folks have been really nice to me over the years, and incredibly helpful, particularly Mark Jacobson, one of their salesmen with some long standing expertise in using this material in building applications (they used to do it in California in the 1980s).
Either one of these materials can be shipped in a much, much more compact form than 4' x 8' x 1" boards.
Foam Boards From Liquids[edit | edit source]
The insulation boards could, in theory, be shipped as liquids. The feedstock chemicals would then be mixed on site in a portable factory, either built in a sea container, or built on the back of a very rugged 18 wheeler truck. On site, in a camp or a disaster zone, the truck rolls in, the chemicals are mixed on site and foam up into the board mold, and are coated with the silver foil.
An 18 wheeler can carry around 36 tons of liquids. Assuming 10 lbs of chemicals per board, that's 7200 boards, or 600 units. At UN occupancy densities (3.5 square meters per adult, if I recall correctly) that's shelter for 2700-ish people per truck. That's beginning to look like a reasonable shipping density.
I discussed this idea briefly with Dow Chemical, who know their way around this stuff (Steve Harasim) and they say "it's not easy, but it's plausible. It's not trivial to get good quality consistent product, there are a lot of factors."
Developing this kind of technology is, I think, a job for the military.
Flat Packed Cardboard[edit | edit source]
This approach to building hexayurts gives a reasonable $100 home ($0.60 per square foot) - suitable for long term use in many areas of the world.
Note this page was revised, December 2007, to revise the price estimate to $160 ($1/sq. foot) based on using a much more durable aluminium exterior. I believe that the $100 home is still possible, but it's going to require vast economies of scale, and developing world material prices. In that context, however, it should be perfectly possible.
http://files.howtolivewiki.com/rapid_deployment_concept.mov (3mb) for some film of hexacomb core and a brief discussion of this approach to making Hexayurts.
Like corrugated cardboard, Hexacomb is flat materials arranged into a 3D form which is much, much stronger. The honeycomb can be shipped "collapsed" - enough material to form the honeycomb center of a 4' x 8' x 1" board is shipped as a solid block 1" x 4" x 6'. (1/6 cu. ft.) The solid block is stretched out to it's full volume by hand or with a simple machine called an expander, which simply grabs the cells of the honeycomb and pulls them open from the flat pack core: it's a simple mechanical device.
The honeycomb is a very strong, very lightweight structure, and it can be filled with blown cellulose (shredded newspaper, for example) to provide insulating properties.
Then the facing materials - something light, waterproof and tough - either tyvek or, for longer life, aluminium-faced kraft paper are stuck directly on to the open honeycomb, forming the panels. A close analogy is shipping corrugated cardboard as a roll of flat material, then corrugating it on site. Hexacomb is about that complex - no fiddly chemistry, just paper, shapes and glue.
To seal the edges of each panel, one can use tape, or have the facing material be significantly larger than the panel, and glue-and-fold the edges over several times, rather like the sealing mechanism on the waterproof bags that kayakers and divers use. This approach removes the need for taping the edges of each panel. Before the panel is sealed, moisture absorbing materials could be thrown into the open face of the panel to help with longevity by absorbing any atmospheric moisture trapped inside during fabrication. The little silica packets that are shipped with items like shoes or computer equipment would be one example of that kind of moisture absorber.
Densities for these buildings are going to be a lot lower than the liquid-ship form documented above. My guess is 400 units a truck, but there are some significant unknowns in all of this. Or about 7000 units per TEU/6meter container
Finally, add a container load of pedal-powered table saws (or a generator and portable table saws, $100 each retail price) to cut the boards, and a crate of tapes per truck.
The other approach is to fabricate the panels using a much simpler and lower tech approach. Rather than the expander and the portable factory, the panels are assembled by hand using unskilled refugee labor guided by a large group of leaders. This approach has the advantage that the refugees are left with an upgraded skill base, which may have utility outside of their immediate circumstances, and the buildings are good enough quality to be useful after the immediate crisis is over, particularly in extremely poor areas.
Here is a projection for cardboard-and-ply-press mass deployments. In this scheme, panels are made by hand, using a simple plywood press. The alternative method, using a mechanical expander and press, is also viable but is not documented here yet.
The process works like this:
- A container load of cardboard, presses and finished hexayurt panels is sent out, with multiple containers of raw materials (hexacomb and facing sheets, glue etc.) following.
- If outdoor conditions are inclement (rain, dust) the finished panels are assembled into factory hexayurts, and the presses are moved inside.
- Panel components:
- Facers (sheets of kraft paper-backed aluminium)
- Assembly and press components and tools:
- Flat table
- Flat dry surface (plywood on 2x4 framing)
- Three plain boards
- One pinboard. This board has hundreds of nails of the correct length pounded through the board in a triangular grid pattern. They will hold the hexacomb in the expanded form. Experiment with pin density.
- Glue roller
- As many refugees as can sit comfortably on one board
- To make a panel:
- Set plain board on table.
- Set pinboard on top of that, points up.
- Stretch out enough hexacomb over pinboard to form a 4' x 8' panel.
- Roll glue over top of the hexacomb.
- Apply a facer to the hexacomb, aluminium side up. Wait 30 seconds for the glue to begin setting.
- Flip over the pinboard like a spatula and drop the glued single-faced panel onto the plain board. Carefully put the pinboard aside.
- Roll glue over the other side of the hexacomb.
- Apply the opposite facer.
- Lift the plain board with the new panel onto
- Put a panel on top. Several refugees sit on the top panel while the glue dries.
- Process notes:
- Keep one board under the whole stack and one board under the top panel. The boards rotate between the stack and the table
- Every 30 minutes, start a new pile, leave the completed pile 30 minutes to dry, and move the dry, oldest pile to the trimming phase.
- Trimming phase:
- Trim and seal the panel edges either with tape or by folding and crimping the edges shut with more glue.
- If using glue, replicate above 30 minute drying cycle.
- Once enough panels for one hexayurt are dry, begin assembly.
$100 per press—2x4s, plywood, nails. some metal rods or pegs. Guess 3 minutes per panel=20 panels per hour per press. Stacks of 20 or 40 panels being left in the press for half hour to dry.
$4.50 for each honeycomb core.
0.1mm thick aluminium foil costs around ten cents a square foot in industrial quantities. This is *quite* durable - you can't get a finger nail or a pencil through it. That comes to, say, $6.50 per sheet, for a total of $11 per panel. The previous estimate of $7 per panel might cover a much thinner aluminium foil coating, and be suitable for limited lifespan applications, but let's price this out for a somewhat longer-life shelter.
Total of, say $12 per panel with panel facings and glue.
- 100 presses = $10,000.
- 100 presses * 20 panels per hour * 12 working hours a day = 24000 panels per day
- 24000 panels * $7 per panel = $288,000 of cardboard etc.
- 24000 panels per day / 12 panels per basic house = 2000 houses per day.
- 12 panels * $12 per panel = $144 per house for panels.
- Assuming $16 of other bits (tape, etc): $160 per house.
Right around $1 per square foot. (Can we get it down to $100 for the entire house? Yes, but it requires enormous economies of scale, and production in a developing world economy. It cannot be done at that price in the developed world.)
- 166 square feet each, or shelter for around five people: roofs over 10,000 per day, assuming there are people to tape up houses and work panel presses.
Now shipping volume.
- A panel weighs about 7 lbs, between facings and core.
- A 20 ft sea container can be loaded to 40,000 lbs (up to about 50,000 lbs I believe)
- 40,000 lbs / 7 pounds per panel / 12 panels per house = 475 units per sea container.
- 475 units is shelter for about 2400 people, assuming 5 per unit.
So you need roughly four 20ft containers per day to keep the presses running. I'm not sure what that is in Chinook loads, but I think it's about 20 runs. A chinook helicopter will carry about half what an 18 wheeler will, so we're talking about housing for 1000 people per chinook run.
Assume the presses weigh 100 lbs each = 10,000 lbs of presses.
Both the presses and the core are heavy enough to be weight rather than volume bound for the shipping container.
So the first 20ft container ships with 100 presses and and as many panels as can be fitted in, to make the "factory" units. Panels fit 480 per full container (or 40 hexayurts per 20 ft container).
I think the approach is to send two to five 20 ft containers of panels or pre-fab buildings, emergency food, water purification tablets and panel presses. Then as quickly as possible get the panel presses going, and ship in the rest of the infrastructure packages.
What's interesting is the cost for 100,000 people comes out to be about $2 million, give or take, just for housing, and more like $4 m ($40 per head) with a very basic infrastructure package. I think those are quite attractive numbers, really.
- http://files.howtolivewiki.com/rapid_deployment_concept.mov (3mb) see some hexacomb material and get a better insight into the system
- hexayurt rapid deployment hinge and lock - an alternate approach from Woody Evans