This post was inspired by my inquisition into Styrofoam dome houses.
From an engineering perspective the principle of using expanded (meaning, puffed-up with air bubbles) polystyrene for dome houses is fantastic. I cannot imagine a more economic, robust, materials-efficient method of containing a given volume of residential space.
The dome shape provides the ultimate in structural efficiency for a self-supporting structure, and plastic molding allows you to eliminate unnecessary material use as the shapes can be perfect (no material mass used for where you don't need it).
Also as an expanded plastic it won't rot, and it's an inherently good insulator. For practical insulation, you can't do better than a thick mass of non-convecting air bubbles.
There is the fire risk concern as plastic can be toxic when it burns, but that concern is mitigated with fire retardants absorbed into the polystyrene, and coatings. And of course there's nothing stopping you from employing fire alarms, etc.
Styrofoam domes would be brilliant in the face of hurricanes in terms of direct wind resistance due to their shape, but not so much for resisting debris due to their low point-loading strength (you could easily shoot a bullet through it). Maybe you would want some extra protection if you're living in some kind of tornado alley, or if your climate is prone to massive hailstones?
For earthquakes, you wouldn't want to be in anything else. You would sooner die from being thrown across the room than from your house caving in on you.
Though I believe that plastic dome's have huge potential for industrial, commercial and many residential applications, I nonetheless believe they may be a thrifty-overkill for much of the mass-residential market.
Aesthetically, it's hard to make a dome that doesn't have an underlying industrial feel to it, and I know that a lot of people will have a problem with that. A lot can be (and is) done to alleviate this problem by breaking the spherical structure up with additions, and matching it to good settings, but the dome-y undertone is still going to be there in the end. They will always look like a bit of a water-tank.
Another more minor concern is the wasted space. Because furnishings and facilities do not fit precisely into a circular floor, the dome needs to be larger than a squared structure for a given domestic serviceability. Dome houses may also require a suspended ceiling for those who do not like the cold spatial feel that can come with an excessively high ceiling.
I have never actually been inside a dome house, but I can say that what would surely be a concern is sound-proofing. The weakness of using low-mass walls is that middle to lower frequencies will tend to cut too easily through them. However, this problem can be mitigated easily enough, and I will talk about it later.
Note: Normal styrofoam for packaging is about a 70-to-1 air-to-polystyrene ratio, making it flimsy. Styrofoam for housing construction is significantly more plastic-dense than this, and likewise stronger.
Following on, I would like to suggest another approach that is crudely related to the styrofoam dome houses, but is what I believe to be a better optimum for a mass-market appeal.
Modular Styrofoam-brick houses:
With the focus being for economical housing, I think using Styrofoam as a structural base would be ideal. The model I believe would be best is modular, lego-style construction. That is, reduce all the components that make up the house to Styrofoam bricks that are about 1-foot square, and also employ larger bricks that are about 2-feet high.
From this base, structural reinforcement would be applied only where required, as you don't have to use expensive materials for the purpose of mere containment and structural integration. This is the core of where you would get your materials-efficiency from. You can also achieve huge savings in labour with this format of housing construction, as a house made up of large, glued-together precision-built bricks can be rapidly erected and with minimal skill.
Getting the cost of labour and materials down is the name of the game.
I would also suggest burying a typical house about 2-feet into the earth, and using a low-height and aerodynamic roof.
With a light-weight Styrofoam roof providing a low center of mass, and low final house height, the building would have inherently high structural resistance to both winds and earthquakes (like with a dome house, but to a lesser extreme). This translates further into a reduction in structural mass/requirement, especially in New Zealand where earthquake resistance is critical and a mandatory building requirement.
The following image shows a plan view of the Styrofoam bricks locked and glued together - forming the walls and the studs.
Some of the bricks would have concrete sections impregnated within them for extra compressive strength, and also for the sake of providing dead-weight mass for acoustic insulation.
The concrete sections will have holes in them so that a thin steel rod can be threaded through the bricks (like beeds) to be post-tensioned on installation. This provides significant tensile strength within the studs, for as required. Also, post-tensioned concrete can provide excellent acoustic insulation, as it will not deflect (at all) from normal dynamic loading (= sound waves).
Many of the bricks will have flutes for wiring and ventilation.
This is the best roofing format I can think of. I can't (yet) see a better way to make a cheap roof that would still be modular-friendly.
The idea is to produce a light, rigid roof with low windage. Think of a freezer panel bloated-out to provide a thick curved side, including cylindrical cavities to remove structurally irrelevant mass. Refer to the following image:
The ceiling would be suspended, maybe with small tension springs to ensure that noise impacting the roof does not (directly) conduct to the ceiling. The large cylindrical cavities provide a substantial air-gap/distance between the integrated ceiling and the upper-section of the roof. With the cavities filled with a lossy sound absorbing material (to suppress harmonic resonance between the boundaries), the double-boundary can then provide for excellent acoustic resistance at lower frequencies. However, the ceiling section may still need to be mildly weighted.
A model design:
The economical housing design I suggest [and this is just an example, of course] is extremely quiet, giving excellent internal privacy. All the main zones (living, kitchen/dining, bathroom and bedrooms) are almost completely isolated from each other acoustically, so the internal styrofoam walls should not need to be weighted (or much). The principle of using wide double-boundaries is strategically exploited everywhere.
The lounge is isolated from the kitchen, because the modern kitchen is too noisy to be openly integrated with the lounge, I believe. However, the kitchen and dining areas are integrated, with the kitchen bench co-functioning as a dining table (requiring some minor adjustment of floor levels). This saves a lot of space and makes the kitchen more practical and social (like a bar).
The segregated lounge has panoramic views and allows for a highly dynamic feel within the house, in turn avoiding the 'living in a box' feeling that small houses are notorious for. The hall area has a section of deep open shelving for all items, making it easy to keep the house clutter-free which also is important for a somewhat compact house.
The more you sprawl a house out with semi-external rooms (like the lounge in my model), the less thermally efficient it becomes. However, if you're using styrofoam for walls and ceilings, and double-glazed windows, this concern becomes moot. Indeed, you can build all kinds of practical and interesting house structures, and cheaply, with a system based on styrofoam modular bricks.
The wider context:
The easiest way to get rid of noise is to put your house in a place that isn't noisy. With new, large-scale residential developments, achieving this is easy if you exploit modern transport technology. I suggest basing new developments on the ULTra system (or similar) to eliminate the noise of cars, and the ugly sight of dominating wide roads. I talk about this opportunity in detail here.
I believe there is vast potential with styrofoam as a fabrication-base for houses, using lego-style modular systems. I can't think of a fundamentally more economical and efficient way to erect durable, well insulated, high quality houses that feel excellent to live in and with explicitly taylorable design potential.
Keeping the system modular on the brick-scale allows for detailed design flexibility. This is important for the sake of optimising the feel of your home. The truth is you can't design a house (properly) until you have a detailed knowledge of the environment it's fitting into. A small but well-designed home can feel great if it works with the context, and conversely a large but inappropriately designed house can feel terrible. Having detailed design flexibility allows you to economically build to the conditions, empowering a good designer to get the most out of any given environment.
Another key advantage of a styrofoam-based house is that it's very light. Making it easy to transport, elevate (on stilts, etc) or even float.
Fabrication for module components can be developed with relative ease using modern tool-making. Check out the following video showing rapid prototyping (for dies), using solid modelling. 3d printing has a lot of potential as well. These are significant enabling technologies for modular house structures of the type that I am suggesting.
To optimise the styrofoam bricks to their function, it would be ideal to make them like bone - dense on the outside, less dense in the center.
You could always make the bricks in two separate sections (an inner and outer component of differing densities), but I would be curious to know if they could be fabricated seamlessly, with the molds producing merging densities in one fabrication phase. This would certainly optimise the strength-to-material mass ratio, and efficiently.
And to note, a density-merging system could also have significant applications with rapid 3d printing, for large(ish) load-bearing structures.
Thinking further, I would imagine many of the reinforced studs would/could be structured as the following image suggests. Specifically, to anchor the whole house.
This structure would require a thicker single steel rod for post-stressing, but it would provide bending resistance on any horizontal axis - making for a simple, reliable anchorage for the body of the house. You could also make these structural components wider than the thickness of the walls (without a significant aesthetic compromise) if you integrated them with the external corners of the house.
Also note that the styrofoam brick becomes in itself the concrete mould for prefabrication. Once you have made your styrofoam brick (very rapidly and cheaply) the wet concrete is just poured into it, to set. This should provide for an extremely economical (and precise) form of fabrication.
3d printing for entire houses is getting a lot of attention as a construction possibility. It's certainly interesting and no doubt has potential, but I don't see the technique being more efficient than building houses lego-style, with big easy-fit-together blocks. Standardised components formed out of moulds lends itself to efficient mass-production for highly affordable prefabrication, and surely more affordable than 3d printing as it's faster to fabricate, easier to transport, and ultimately requires less material due to greater precision that can be achieved with moulds.
Anyway, the following video shows us a house being fabricated with 3d printing. It uses recycled materials. It comes from this article.
I think 3d printing has serious potential not in a prefabrication factory, but on-site building new large-scale developments - entire townships and suburbs, ranging from maybe 50 to 5,000 houses.
3d printing could be a superb tool to this end. A highly mobile concrete printer could run through a development printing appropriate structural components for houses (to be later fitted with other materials) and all kinds of civil infrastructure - water tanks, outdoor paths and stairs, pond and pool linings, a castle in a playground, an outdoor stage...whatever!
However to achieve this, you need a mobile printer - not something that operates on rails and only moves in a straight line and on flat ground. For the sake of perspective, the following image gives you my rough guess as to what a flexible mobile printer would be like. It would compensate for the poor rigidity by using robotically-active stabilisation. The technology to provide this kind of precise stability in a flexible crane is here today.
In operation you would mount two polls on the construction site (like cellphone towers) that allows the concrete printer to know its exact location down to a very small area within the development. With the houses and infrastructure already designed on a computer, the printer would move around the site systematically doing all the foundation concrete work, automatically, for the houses (and other) to be completed later.
Again, on this level, 3d printing could be extraordinarily efficient and make for some very interesting residential developments. But again, this I believe is where 3d printing belongs. We have better options for most other prefabrication work.
3d concrete printing, mass-produced composite bricks for pre-fabrication, and full-automation network-based transport (here) could all work together to drastically reduce the cost of urban developments, while at the same time revolutionising their liveability.