Modern straw bale technology is a long way from what you're describing, and it's by no means an impermanent structure: a lot more than straw is involved. Otherwise, local building/planning departments would never have approved it. Mud or clay mixed with straw is called "wattle and daub": it's an ancient, and very impermanent, building technology suitable for very dry locations. So developing a 3D printer for this material mix wouldn't be very useful. There are 3D printers that use dirt or other powders mixed with a binder of polymer for buildings, those exist and/or are being developed by architects. We've reported on a few of them.
Ann, I suppose that straw should indeed last a lot longer than hay, since it has much less food value and a whole lot less moisture. I can see that hay bales with cement sprayed on the outside could resist the weather, and if they were covered with adobe on the inside the fire hazard would be small. But I don't think I would count on them for structural strength for the long term, since they are still organic materials with a very high surface to volume ratio. Fine for a single story house but probably not for a multi story residence.
How about a machine to 3D print with a straw and clay mix? It would need to have a robot that could build walls, so it would certainly not be a traditional machine. But it is certainly within the grasp of present technology. If anybody develops this concept and is a big success, they owe me a lunch.
Well, that explains it. What you describe and the modern straw bale technology are worlds apart. Basically, straw bales are used inside the walls and protected, of course, from weather. So the walls are super thick and it's excellent insulation. Many very old building technologies are way better than what we use now, which is determined more by commercial interests than by practicalities.
Ann, I was thinking about a hunting lodge that had been built with old hay balesthat were a really good deal, from what I was told. I visited it in it's third year and it was not so very wonderful at that time. But it certainly was a lot warmer than a tent in that part of Michigan, in November. I don't think that anybody chose to use it in following years.
William, it rains here, too. Straw bale houses aren't what you think they are: I suggest you try googling the technology. All those problems have been solved by the construction methods used. The code was changed here to accommodate that house and the technology, and it's been changed elsewhere as well.
I would not want a straw bale house in Michigan primarily because it would not last very long. We have way too much rain and snow, it would absorb enough moisture to decompose, and then it would be unhealthy to live in as well. But in those counties that avarage a half inch of rainfall during a monsoon year a straw house might work out quite well.
Besides that, there is a real problem with the inspector simply "not liking" something, and with nothing in the code saying it is OK, the only recourse is an expensive lawsuit. So the person gets his way just because he can, with no valid explanation even offered. This is why so much work is done without permits or inspections. Common sense is often not allowed. And it seems that some of the local codes predate many modern inventions of the past few years.
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