There has been a lot of publicity about 3D printed housing lately, and it is not surprising because the notion seems almost unbelievable. What is not to like about being able to almost instantaneously convert practically any plan into reality for very little money? This article from fastcompany.com describes such housing that is being developed for masses of poor people in El Salvador and other third world countries. They claim that this can be done for under $4000 per house!
So, is this for real? Well, not quite when you check into the details of what is being accomplished. They say that the walls can be printed in less than a day, but then that still leaves fabricating a roof, adding windows and doors, and all of the standard utilities (plumbing and electricity). It is not clear, but it appears that the $4000 price is just for printing the walls, which require the massive machine that is assembled at the building site.
Then there is also the question about how sustainable this approach really is? The walls are printed using some proprietary formulation of cement, the manufacturing of which is one of the most polluting and energy-intensive industries around.
And then how well insulated are these houses? They claim that they are very energy efficient because they are composed of lots of thermal mass. Well, thermal mass and insulation are two different things, and thermal mass alone will not provide a well insulated house. If you look at the printing of the walls in action you can see that they are composed of truss-like patterns of interior braces between the inner and the outer walls. This pattern alone will not provide much insulation because of all of the thermal bridging.
It is possible to print houses with cellular lightweight concrete that can provide up to R1.6 per inch. At this rate an 8″ thick wall would be about R-13, which wouldn’t provide enough insulation for most energy codes in the U.S. The formulation that they are using with the technology described may not even be that good.
So my attitude about all of this is that there is real promise in the 3D printing technology, but one needs to be careful to evaluate many of the claims that are being made about it.