Additive Manufacturing and Construction
The Integrated Design received a grant to develop a 3D printing process for the construction industry using a wood-based material. Details on this project can be found later in the article.
Additive manufacturing, better known as 3D printing, is an emerging technology that some have claimed will usher in a 4th industrial revolution. It has already changed product development practices by enabling rapid prototyping that speeds up development timelines for new products. Most colleges and high schools have 3D printers available for their students to learn this new workflow. In addition, there has been extensive time and effort put into developing processes and printer designs that can print with different structural materials, like metal, nylon, and carbon fiber. Metal 3D printing has been transformative for the aerospace industry because it can make specialized low-production components. The construction industry is poised for significant disruption if 3D printing can crack the nut on large scale printing techniques and regulatory hurdles.
What is 3D printing and how did it start?
Additive manufacturing is a technological process that can build parts using plans generated in a software program, normally by breaking down the part into multiple layers. The printer is then able to create these layers using a controlled feedstock material and stack the layers on top of one another until the part is produced. This technology has been around since the 1980s and the first patent that was successfully granted was to Charles Hoyll in 1986 for a Stereolithography apparatus (SLA) printer. It uses a UV Laser to solidify a photopolymer resin contained in a tank and builds the part layer by layer as seen in figure 1. This is similar to a resin 3D printer available online starting at prices around $300. Another very common 3D printing technique was invented and patented in 1989 called Fused Deposition Modeling (FDM). This works by pushing filament through a hot extruder onto a hot bed, again printing it layer by layer. This has become an incredibly popular method for rapid prototyping.
Figure 1 - Example of SLA (left) and FDM (right) printing techniques.
Rapid prototyping was the entry point of 3D printing in the construction industry with architecture firms using it to build scale models of buildings. However, it wasn’t too long afterwards that firms attempted full-scale 3D printing for construction was pursued. USC professor Behrokh Khoshnevis was the first to make a full-scale wall section using a concrete feedstock material and a gantry style printer. The process developed is similar among other large scale 3D printers that are currently under development. You can see the initial 3D printing process flow in the video below. https://www.youtube.com/watch?v=-yv-IWdSdns&t=224s
With this prototype and the printability properties concrete possesses in its pouring states, concrete has “cemented” itself as the primary material for 3D printed construction.
What are the reasons we are developing this technology?
There are quite a few market pains in the construction industry, especially when looking at the residential and light commercial spaces. Housing demand is outpacing current supply, leading to a shortage of houses. The demand for housing is expected to increase substantially through 2030. This is especially concerning in cities that are continuing to grow rapidly.
The second issue facing construction is that there has been a long-term shortage of skilled construction workers. A survey of over 2,500 construction firms conducted by the Associated General Contractors of America found that 80% of firms had a difficult time filling open positions . This is also combined with the construction sector lagging behind other sectors in the economy in terms of productivity gains in the last year .
In addition to making more housing, there is a great demand for housing to be sustainable and energy efficient. This can be done by reducing the energy load that buildings consume, which is currently about 40% of the total energy used in the US. If we look deeper into that statistic, a substantial portion of that energy is being used for HVAC. One effective measure to reduce loads is by creating a more airtight envelop and adding insulation. With all these market pains, how can 3D printing help solve some of these problems?
Benefits of 3D printing
In 2020 the market for 3D printing in construction had an estimated market size of $7 million and is projected to reach $1.2 billion by 2028 globally.
The main benefits touted by 3D printed construction advocates is that it reduces time and costs. To understand how much 3D printed buildings cost, 5 different case studies on 3D printed buildings were used to determine the cost per square foot. This was then compared to other means of construction for different building types, which is shown in the table below. There is a big cost advantage that 3D printing has over its competitors. These valves are preliminary figures in a field that is constantly evolving. The labor cost to run the printer, cost of setup, and the cost of the printer itself may not be reflected in the provided estimates. When the technology matures, it may prove to be cheaper on cost per square foot basis than conventional methods
How long does it take to print a building? ICON was able to print a 500 sq ft home in about 24 hours start to finish on an affordable housing project in Mexico. Once the printer is started, there is little need for manual labor during the printing process. This labor is mostly limited to placing support beams in place to frame windows and doors. For the projects used to estimate the cost per square foot, the printing time ranges from a couple days to a couple of weeks depending on the scale of the project and the printer used.
A second benefit from this method is the waste reduction. Currently, waste generated by the construction industry topped 600 million tons in the US for 2018. 3D printing can almost eliminate waste material in construction because it relies on an additive process that only uses material where the software intends. Utilizing robotic machinery to make the building also limits human error while on the construction site and reduces risks in terms of worker safety. The last benefit worth noting is the opportunity to design complex and flowing designs without having major construction costs.
What are the barriers to overcome?
The first barrier to 3D printed houses is that they need to meet the current building code standards. The current code is designed to standardize construction methods that are already established like wood framed, CMU, and steel framed structures. The 3D printing process is constantly evolving to find an optimized composition of a printable and long-lasting material. This makes it more difficult to prove the finished building meets the structural, fire and safety codes needed to gain an occupancy permit for the building. To address this issue, standards are being updated to allow 3D printing structures to prove their compliance. For example, UL 3401 is an outline released in fall 2019 that helps regulators evaluate different building elements created from 3D printed processes. A recent project developed by SQ4A created a 3D printed 1500 sq ft, 3-bed, 2-bath house in Rockfield NY, and was able to achieve a full occupancy permit this year. It is currently listed for sale on Zillow with a pending offer. Another project in Germany was also able to achieve a full occupancy permit, showing the race between countries and companies to be the first. This is a barrier that is slowly being overcome and we will most likely see more demonstration projects coming soon.
The next issue in the industry is that the feed stock material and the finished structures are energy intensive products. Concrete has a high embodied energy value compared to other common building materials because of the high temperatures required for the manufacturing process. The 2,700 deg F temperature range is very difficult to reach without using fossil fuels. Another issue with concrete is that it is not as insulative as other common construction materials. In 2018, one of ICON’s first attempts at a 3d printed house was not able to meet the local energy codes. ICON was able to get an exception for this issue from local regulators, but this is concerning. A desire to embrace 3D printed buildings by permitting poor performance could lead to quality concerns and hamper the adoption of 3D printing as a sustainable and desirable construction method. It could very well become associated with cheap affordable housing projects and lead to a perception similar to manufactured homes in the 1970s.
There are other startup companies that are experimenting with more environmentally friendly materials. Gaia is one example and is using a locally sourced a biomaterial made from rice husk and rice straw as a feedstock material for their 3D printed buildings. TECLA is a recently completed project that shows the architectural freedom and the material used in action.
The Integrated Design Lab is also conducting research into environmentally friendly feedstock material for 3D printed construction. With the help from the Higher Education Research Council IGEM grant, we are developing a process to produce building assemblies using a recycled wood-based material. We are currently studying feedstock compositions, different extrusion processes, material properties and the life cycle environmental impacts.
Another issue to consider is the scalability of 3D printed buildings. There has been a lot of focus on building 500-1500 sq ft houses as demonstration projects. However, limitations on printer size prevent its use on larger projects. China currently claims title of the tallest 3D printed structure, with a 6-story apartment complex located in the greater Shanghai metro area. This structure was printed at an offsite factory and its components were assembled on site. The biggest onsite 3D printed building is in Dubai, which built an administrative office building. They used a robotic arm that printed sections of the building one space at a time. The process took about 17 days to print the 6,800 sq ft building and cost around $140,000. Other methods are seeing 3D printed construction being combined with traditional construction techniques to make larger multistory houses and offices, but the technology is still far off from creating medium to large commercial or industrial buildings.
The last issue, (and probably least certain), is the adoption of this technology within the construction industry and society. There are a lot of barriers for a traditional construction business to use the 3D printed process. The first is the cost for the 3D printer machine and to train workers to operate it. There is also a logistical challenge on how to transport and setup a printer in a dense urban environment, which depends on the design of the printer and the printed structure. Then once the house is printed, there is going to be limited ability to conduct major renovations and will probably come with significant costs. The other major concern is the public perception. Are people going to want to live in these structures and create a home, or is it going to become a symbol of cheap housing. The exterior finish of the printing is definitely a distinctive design characteristic.
With the vaguest answer available to mankind, maybe. It is better summed up with “Ask me in 20 years, I’ll know the answer then.” All joking aside, it is difficult to predict how the technological, regulatory, and societal considerations will play out in the upcoming years. This largely depends on the ability to deliver both affordable housing for cities that are struggling to keep up with increased housing demand, as well as creating a desirable and energy efficient dwelling that people want to live in. There is also a competing process in offsite manufacturing that could offer the same benefits. We will have to wait and see if 3D Printed is the wave of the future.
Prototyping 3D printers were able to take off in the consumer market in the 2010s due in large part from the initial patents on the printer design expiring.
Tais graduated from Boise State University with a bachelor's degree in mechanical engineering and is pursuing a masters degree in mechanical engineering at the University of Idaho in Boise. He is working as a graduate research assistant with IDL with a primary research focus on cellulosic 3d printing for modular building assemblies. Outside of his studies, Tais enjoys skiing, hiking, and general outdoor recreation.