3D printed houses have been steadily gaining popularity and with time multiple aspects of the technology have been put to the test.
These include structural strength, durability, cost, and safety. One important aspect of safety is the fire resistance of a house. In the case of a fire breaking out, a house should be able to withstand the effects for an extended time so that the tenants can evacuate safely.
Conventionally built houses have multiple layers of safety that give them fire resistance. This includes several construction techniques (which have been tried and tested) that are implemented to make them fire-resistant.
So, what about 3D printed houses? Are they fireproof? The answer is yes. 3D printed houses are fireproof. Depending on the type of 3D printed house, it can have multiple layers of fire safety built right into it. This can include the use of thicker walls, incorporation of active fire mitigation measures, or the use of fire-resistant construction materials. All these methods can also be used together in unison. Although there are several factors to consider, it is safe to assume that 3D printed houses have sufficient fire-resistant capabilities built into them.
Before we take a deep dive into the methods employed for fire resistance, it is important to make one important distinction and that is the material used for constructing the 3D printed house.
What about the cost of 3D printed houses? Check out article on costs here.
We also suggest reading our article on 3D printed houses durability to get the full picture and understand how 3D printed houses are safely constructed.
What material is used for 3D printed houses?
Multiple materials have been tested over time for 3D printed construction. This includes concrete, wood, and clay among others.
However, most of these materials are in the early stages of their development and most of them are yet to be tested for large-scale implementation. This includes factors such as durability, maintenance, safety, and structural integrity.
This applies to all materials but concrete. Concrete, long before 3D printing was even invented, has been used widely used for construction. It is one of the most durable construction materials and it also happens to have excellent fire resistance.
Concrete, due to its workability and flexibility in its wet state, is also a perfect material to be used for the 3D printing process. It can be extruded easily, and it can be modified so that it sets quickly.
The layering process of 3D printing makes concrete a very suitable choice as a construction material and a large majority of the 3D printed houses built up till now have been concrete ones, so we will primarily focus on those.
Are concrete 3D printed houses fireproof?
For concrete to be used in 3D printing, not many changes have to be made to its chemistry. A few additives might be added to promote quicker setting times, but that is about the extent to which modifications are usually made.
Since concrete is being used in its default configuration, it can carry over the fire-resistive capabilities that it has. Concrete does not burn and has a very low heat transfer rate (it does not spread heat very efficiently). (Source)
In addition to that, concrete members are also able to withstand loads under high-temperature conditions. It means that if a fire does break out, the concrete building can stay structurally intact for a long enough time for safe evacuations to take place.
This is a really important aspect to consider, especially because many other materials do not possess this prolonged fire resistance.
Now that we have established concrete as a safe material, let’s take a deep dive into the methods used in concrete 3D printed houses that make them fire-proof.
Which methods are used to make 3D printed houses fire resistant?
There are multiple ways through which this can be done. Since 3D printing offers the flexibility of printing almost any shape, geometrical patterns can be used effectively to increase the fire resistance of structural members, like walls.
3D printers can layer concrete such that it creates voids and an air insulation layer. These cavities serve as a fire retardant and prevent the fire from spreading. Its effectiveness has been proven through extensive peer-reviewed research. (Source)
Another method that is employed is the use of alternative reinforcement materials for strengthening the structural members. Steel is particularly notorious for having poor fire resistance and it quickly loses its strength under high temperatures.
In that case, fiberglass reinforcement can be used. It not only is lighter and stronger, but since it has a lower heat conductivity and a high melting temperature it can withstand the effects of fire for longer while maintaining its structural integrity.
Other reinforcement materials have also shown improvements over steel rebar, but overall glass fibers have shown the highest thermal resistance. (Source)
Which factors affect the fire resistance of a 3D printed house?
In a concrete 3D printed house, many variables can be modified to increase the resistance of the structural members to fire.
Research has shown that altering the thickness of walls just by a few percent can considerably improve fire insulation. In addition to that, the density of the wall can also be modified to increase the fire resistance and it is proven to be more effective than thickness changes. (Source)
These methods are effective not only because they are easy to modify (A 3D printhead is quite versatile and the dimensions of the layers can easily be changed), but also because the additional material being used does not affect the cost by much.
That is because concrete is a widely available material, and the cost of the additional material is compensated by the advantages that it serves. When compared to the additional price of the concrete, repairing a house after a fire would be much more expensive.
Since wall density is more effective at stopping fires than wall thickness, a hybrid of high density and cavity walls can be used. This also cancels out the cost of the additional material required, since less material is being used overall.
One slightly unintuitive factor that also affects the fire resistance of structural members is the load that it carries.
Researchers have found that walls that are under higher loads tend to have better fire resistance in comparison to walls that have lower loads or are free-standing. (Source)
Although the reason for this behavior is not yet understood, there have been many hypotheses as to why that happens. One reason could be the pressure that the wall is under. It causes the wall to be compressed and hence prevents spalling (chipping of concrete from the surface).
Without sounding too scientific, the addition of pressure has something to do with molecular changes in the concrete matrix and that ends up making it more resistant to fires. You can refer to the source above for more details.
All these methods (in addition to improving fire safety) are cost-effective and maintain the low construction costs of a 3D printed house, which is one of its biggest selling points.
What is Rockwool and how does it improve fire safety?
Rockwool is widely used in conventional houses as an insulator, and it also happens to have great fire-resistant capabilities. It is manufactured by weaving together a mixture of molten rock fibers and ceramics.
Rockwool has shown great fire resistance in the cavity walls of 3D printed houses. In comparison to an air-insulated cavity wall, a Rockwool insulated cavity wall has better fire-resistive capacities and it outperforms an empty cavity wall in almost every test condition (be it insulation or thermal resistance). (Source)
Since this is also a widely available material, the cost addition is minimal. The material is also lightweight, so it does not add any considerable load on the structural members of the house.
Are 3D printed homes safe?
This is after all the most important question that homeowners want the answer to. There are several factors to consider here, but on a general basis, 3D printed houses should be as safe to occupy as conventionally built ones.
They are structurally sound, durable and as we have seen above, they have ample fire resistance as well.
If you are still not convinced, you can refer to interesting posts here and here and our post on hurricane safety where we cover other aspects of safety and durability in much greater depth. All the claims in these posts have been backed up by rigorous peer-reviewed research and in my opinion, all the indications have been optimistic.
It does not mean that there are no improvements to be made. There is always room for improvement and that is the greatest thing about technology.
We always strive for the next better thing and that approach has led to some fascinating advancements throughout history. If I say that 3D-printed houses are among those advancements, I would not be wrong.
There is much to learn and much to improve, but the future of the technology is bright and hopefully, we will see it being implemented on a much larger scale in the future.