Offsite construction is often misunderstood. To be fair, that misunderstanding stems from legitimate sources that have tried and failed to derive the value from offsite construction.
That history is more confused by the actual definition of offsite construction, which has had many starts and stops for decades. About 20 years ago, the industry already had plenty of experience, just not loads of success.
While sustainability in the construction industry was gaining traction, the popularity of offsite was growing. The construction industry was miles behind other industries with sustainability practices, and offsite construction leaders recognized the opportunity it had to make a powerful, positive impact with better building practices.
While the industry is starting to recognize the potential of offsite for better performance, as shown in this COGNITION Smart Data, there still is slow adoption. Nearly 60% of respondents believe that offsite construction has the potential to elevate sustainability, yet according to the National Association of Home Builders, only 3% of homes are built offsite.
“Sustainability has always been a big benefit for offsite,” said Mark Lee, formerly with MiTek and now an offsite consultant. “Numerous studies have demonstrated anywhere between 40 or 50% savings on embedded carbon.”
The main way that offsite contributes to more sustainable construction is by reducing waste, he explains, which is done both by minimizing waste with the optimal use of materials, and because by using BIM in the design planning stage, a more accurate bill of materials can be created leading to more thoughtful use of materials.
And, while the history is a bit jaded, the future is open to possibility as the technology is proving to deliver on lowering carbon beyond what conventional construction can do, starting with a more optimized process.
Being in a controlled environment is a big benefit to the sustainability of offsite construction. Designs are complete and scrupulously followed when a project is offsite, as compared to onsite construction where designs, measurements, and plans can change daily.
While the opportunity is there for offsite to play a larger role in more sustainable construction, Kelly Hampton, the chief brand officer at offsite building company Neovi, says the evolution has been slow and minimal.
In the offsite process, there is a higher level of technology use that is leveraged from design and manufacturing to assembly. This use of technology also creates efficiencies that aren’t possible onsite, including ways to limit the number of “touches” and movement required during the building process.
In offsite construction, there is much more coordination with quality assurance programs, such as design, modeling and technical tools that can optimize the raw materials. For instance, instead of using a 12’ board for a 7’11” cut, a program will inform the labor to use an 8’ board, which immediately reduces waste.
In France, Sofiane Ben Maamar launched Bim’Steel a housing manufacturer that can build 70% faster, which can reduce carbon and cost by up to 30%. Up to 90% of a unit is finished in the factory so that there is less waste and so that material use can be optimized. Plus, all raw materials are 100% recyclable.
“Our new factory will enable us to renovate and build nearly 20 homes per day according to low-carbon standards,” Maamar said.
The efficient processes of offsite construction require equally efficient supply chain logistics, particularly since transportation plays a larger role.
There are several approaches to reduce the impacts of transportation on the overall environmental impact of offsite construction. The transportation requirements vary from a volumetric offsite project to a panel-based method. With volumetric, there is more waste since the module is completely built, and then requires more shipping space, which can be considered shipping a lot of air.
“You can create hub and spoke type models instead,” said Lee. “By creating sub-assemblies that can be finalized closer to the job site, you can minimize shipping air.”
Regardless, offsite construction helps reduce carbon by limiting the number of trips that trades might have to a job site. Offsite has more structured logistics to manage both planned and unplanned trips to the job site.
Other developers are looking at minimizing the cost and environmental concerns of transportation by creating micro-factories. Brian Gaudio, CEO at Pittsburgh-based Module, points out that traditional modular factories are located far from population centers, so his company started a small micro factory in Pittsburgh.
The homes are manufactured to Passive Haus standards for the highest level of sustainability.
“The module is 40% faster to build, 70% more energy efficient and has 10% lower operating costs,“ Gaudio said. “The manufacturing is core, and good design is what ties it all together.”
There also are future opportunities to reduce carbon with new and different materials.
Since the assemblies and sub-assemblies are made with high precision, the offsite manufactured project has a tighter envelope to reduce operating carbon. Plus, with better envelope performance, the demand on the HVAC also can be reduced, lowering those operational carbon costs.
“The principle evolution has been from one of lower waste to considering alternative means to building,” said Neovi’s Hampton. “As new and better materials and methods have come to be used in the construction industry, they have found a place in offsite construction. Good examples of these are CLT and steel. In many cases, these new materials, such as steel framing, are best suited for offsite construction.”
Neovi is focused on materials that can improve the overall quality of the living experience. Neovi uses steel framing for better precision, plus it’s non-combustible, it doesn’t rot or mold, it is seismically stronger and also is pest resistant. Neovi also roll forms the framing within their factories to minimize waste.
Fairly unique to Neovi is a move from drywall to solid surface throughout the home as a rigid material that can’t be easily damaged. This means less waste from damages, and less waste because the same material is used throughout, which optimizes cuts.
Bim’steel is taking a unique approach to materials with decarbonized steel as the primary structural material, which is 100% recyclable. Plus, the roof and wall insulation are bio-sourced wood fiber. The homes have a high-performance solar control glazing to manage heat as well and together these features add up to net-zero carbon emissions and net-zero energy consumption.
“We are setting a new standard in sustainable housing,” said Maamar. “Bim’Steel aims to be in the U.S. this year. In six months, we can set up a production line that could start producing more than 1,000 homes per shift with 10 workers.”
He estimates costs between $35 and $40 million to set up a normal production line with 14 robots and the 10 workers that would be capable of producing those 1,000 housing units.
Bio-SIP offers another unique use of innovative materials. It is a modular panel system made from recycled plastics and natural fibers that has low embodied carbon, can be built quickly, offers good thermal efficiency, and is fully recyclable at end of life.
“I got into green construction out of sheer frustration,” said Justin Murray, the COO at Bio-SIP. “The way homes are built in the U.K. is slow, wasteful, and unsustainable. Tiny little bricks, mostly just for a rainscreen, slow the process down and demand highly skilled labor. Globally, house building is crying out for a revolution. We need homes that are fast to build, affordable, energy-efficient, and sustainable.”
Bio-SIP homes are net zero, designed to be manufactured in micro-factories, and assembled onsite. Instead of volumetric modules, the panelized system makes logistics simpler, plus sets the company up to deliver the quantity and quality needed by the market.
The future of offsite construction is very promising for both the affordability and the sustainability of tomorrow’s housing.
Lee expects that by leveraging BIM in the design and planning, the models themselves will provide the platform to predict carbon in a design.
“The key is in the application of the BIM modeling to include carbon modeling it,” he said. “You change the bill of material if there is good data on the carbon of those materials, then you can model for that and create a better design.”
Technology improvements in things like automation will further improve performance in offsite construction. Plus, Hampton predicts that the data available to offsite companies will support better decisions, like being able to utilize Environmental Product Declarations to then select more responsible materials.
Transportation will also become more sustainable when its electrified and won’t be such a weight on the carbon scoring of offsite construction.
Consumer demand also will force more builders into the realm of offsite construction.
“If one company can build more sustainably, without increasing costs, others will need to find ways to follow suit,” Hampton said. “Buyers will expect and demand it. If you can have a home that will forever be mold and pest free at the same cost, or less, than a traditionally built home, wouldn’t you want that?”
Right now, COGNITION Smart Data shows that only about 27% of survey respondents felt that offsite construction is a great opportunity, but the shift is happening and needs to happen to align with sustainability goals.
“For us, offsite construction isn’t just a method — it’s the only practical way to deliver better homes for people and the planet,” Bio-SIP’s Murray said.
Publisher’s Note: Green Builder's 20th Anniversary celebration is sponsored by: Carrier, Trex, and Mohawk.