OFF-SITE : Industrializing construction for the low-carbon cities of tomorrow

The construction sector is facing a triple revolution: environmental, digital and
industrial. Its historical model is running out of steam, and it is urgent to consider
new models associated with new, more efficient methods of design and construction.
How can off-site construction, by combining prefabrication and industrialization,
represent a major solution to the complex issues raised by urban densification,
economic difficulties in the sector and the urgency of decarbonization? How can
off-site production help meet the challenges of today and tomorrow? What are the
promises of this new approach, positioned at the heart of transitions?

ADEME defines off-site construction as «a construction or renovation process integrating the design, prefabrication, logistics, quality control, on-site implementation and end-of-life dismantling of building subassemblies that have been produced off-site». It’s a collaborative approach based on the use of factory-prefabricated components, then transported to the construction site, which becomes an assembly site.

Before being a technical or technological revolution, off-site construction is first and foremost a methodological revolution, at the interface between process and product innovation, serving objectives of quality, timeliness, profitability, safety, ecology, the circular economy and the life cycle.

ECOLOGY, DIGITAL AND INDUSTRY: CONSTRUCTION’S TRIPLE DEBT

With an ecosystem struggling to master its primary purpose – i.e to build within a framework of controlled costs, deadlines and quality, reduced environmental footprint and improved workplace safety, all with a significant scale factor – the construction sector is facing a daunting challenge. It must reinvent itself and undergo a deep transformation within a tight timeframe.

3 key figures highlight the challenges facing the industry:

• The carbon footprint of the building value chain
  represents 153 Mt CO2e in 2019, or 25% of France’s annual carbon footprint1.
• Less than 6% of projects use BIM.
• The sector’s productivity has declined by 20% since 2001.

With nearly 427,000 companies and an average of less than three employees per company, the French construction sector is fragmented. The multiplicity of small businesses operating in diverse geographical areas, with little capacity to invest in training and R&D, appears to be one of the explanations for the sector’s chronic innovation deficit.

The retirement of baby-boomers, who represented a large pool of skilled labor, is generating a marked increase in the cost of non-quality. According to Agence Qualité Construction, the number of damage claims has risen by 6.7% between 2012 and 2021. In concrete terms, this means lower productivity and higher insurance premiums for over a decade.

[1]Extrait du rapport « Feuille de route décarbonation du cycle de vie du bâtiment » – https://bit.ly/3JvrfPd
[2]Baromètre 2020 du PLANBIM2022 – https://plan-bim-2022.fr/wp-content/uploads/2021/03/Barom%C3%A8tre-BIM-2020-Infographie-4-pages-v4.pdf
[3]https://www.lemoniteur.fr/article/ameliorer-la-productivite-dans-le-secteur-de-la-construction-en-france.2294577
[4]Rapport FFB « Le bâtiment en chiffres 2022 » – Juin 2023 – https://www.ffbatiment.fr/le-batiment-en-chiffres
[5]Agence Qualité Construction – Url – file:///Users/alice/Downloads/r-observatoire-qualite-construction-2023-aqc.pdf

Despite its proven benefits in the final quality of structures, by managing substantial flows of information with a high level of precision, Building Information Modeling (BIM) remains underdeveloped in France. Except for complex or large-scale projects, very few «standard» projects make use of BIM.

There are many reasons for this, but the main one remains the challenging valuation of the ROI of such an approach in an ecosystem that is still poorly trained and lacks interoperability. The discontinuity of the digital flow between the design and construction phases prevents the exploitation of the benefits of BIM during the operation and maintenance phase.

Because its industrialized components are natively digitized, the off-site approach should bridge this gap and promote the deployment of a highly digitized value chain.

OFF-SITE: A MODERNIZATION LEVER FOR A MORE EFFICIENT AND EFFECTIVE VALUE CHAIN

From relatively simple elements to 3D modules 95% prefabricated in the factory, the «off-site» approach relies on components of variable scale. The Anglo-Saxons use an indicator called «PMV» (Pre-Manufactured Value) to determine the level of «off-site» applied to a given project.

By moving from a logic of monofunctional materials to a logic of multifunctional constructive systems, off-site involves revolutionizing working methods to make the value chain more efficient.

To fully exploit the potential of these new constructive processes, it is necessary to approach the development and design of projects in a new way, by integrating upstream certain input data from the constructive systems themselves. Design is no longer done from a blank sheet of paper, but from components or constructive systems that are integrated into projects. This methodology is known as «DfMA» (Design for Manufacturing & Assembly). To achieve this, it is essential to be able to collaborate from the outset with a multi-disciplinary project team, moving from a sequential engineering logic to concurrent engineering.

Project performance necessarily involves selecting the most suitable construction processes right from the development phase. This shift of engineering to the earlier phases of a project is not neutral with regard to procurement processes, and requires anticipation of decision-making, including the selection of providers and contractors.

Reduction of timelines, increased perceived quality, reduction of construction site nuisances, improved worker safety… During the construction phase, the benefits of off-site construction are numerous but involve considering new constraints, and new skills are required to ensure the success of a project. The prefabrication of large-sized components has a major impact on logistical organization. Transport and storage become key parameters for the success of an operation ; and mastering them is essential to guarantee easy assembly of elements on-site.

The acceleration of construction times is particularly attractive in a context of rising borrowing rates, where financial costs are increasingly weighing on the balance sheets of operations.

However, beyond the speed of execution, moving a part of the construction site to an out-of-town factory generates a significant reduction in nuisance for the neighborhood, thereby increasing its acceptability for the surrounding community.

By transferring construction to a controlled environment, with stable weather conditions throughout the year, workers also enjoy a safer working environment that is conducive to training, while the implementation of industrial quality assurance plans guarantees unrivalled control over the quality of prefabricated factory products.

Developing industrialized construction is also a response to the challenges of revitalizing employment areas. By establishing production plants in vulnerable territories, off-site construction helps workers from relocated industries return to work. It’s a good way of spreading the metropolitan dynamism to more remote areas.

OFF-SITECONSTRUCTION: A LOGIC OF INDUSTRIALIZATION

Off-site construction operates in a logic of industrialization often compared to the post-war prefabrication wave in France. However, despite of similarities in both approaches, allowing the construction process rationalization, the post-war goal was to urgently rehouse and build quickly, in a context where labor was abundant and architectural requirements were limited. Today, this new quest for industrialization carries very different ambitions and values, around new societal, industrial, ecological, and digital challenges.

Historically, building design is based on a prototype logic. There is no repetitive or standard approach; everything must be reinvented for each project.

Industrialization implies radically changing this vision, relying in particular on the notion of a «product.» There will be no industrialization without productization. Thanks to its complementarity with digital tools, whose power should allow achieving a high level of variability without compromising the efficiency of an industrialized production chain, off-site construction holds the promise of contributing to overcoming obstacles to the industrialization of construction, up to «industrializing customization.»

This new paradigm implies strengthening synergies between the various players and overcoming the lack of interoperability between systems. It calls for a redefinition of the way engineers and architects work together, at a time when increasingly complex buildings must meet ever-more demanding standards, leading to a growing complexity in the architect’s profession. If he is to retain his role as master of design, the architect must gradually move towards mastery of these new, more technical elements. With this in mind, ESTP, in partnership with ESA, has created an excellent dual degree in architecture and engineering.

The fact remains that buildings will never be manufactured products like in other industries and will always be part of a specific urban context, with a high level of intrinsic variability.

While off-site construction meets a wide variety of needs, it is not suited to all projects. Depending on the context, the right mix of off-site and traditional construction processes needs to be determined in advance. The most important thing is to meet the need as precisely as possible. A revolution, then, but one that does not aim to make traditional construction disappear.

«OFF-SITE CONSTRUCTION WILL BE ECOLOGICAL OR WILL NOT BE»

Use of dry and bio-sourced materials, short supply chains, waste reduction, reduced logistics flows onsite and easy deconstruction of buildings : from an ecological point of view, off-site construction in France offers many advantages, even if the industry lacks structured data to valorize these benefits.

It’s not only about building but about designing a new, more virtuous model, from design to deconstruction. The intrinsic ability of off-site construction to facilitate dismantling and recycling allows envisioning future buildings as adaptable or even movable, with a drastically reduced environmental impact. While not all buildings are intended to be moved one day, this approach remains highly interesting in the off-site construction’s ability to be integrated into a circular economy logic. In the same logic, the high level of digitalization of off-site products means that buildings can be seen as banks of materials, where each element is identified and referenced for future dismantling and reuse.

REBUILDING THE CITY ON THE CITY

Renovation is often the most effective way to reduce the carbon footprint of real estate. With almost 80% of the buildings in 2050 already existing, and regulations limiting soil artificialization, new construction is likely to slow down in favor of increased energy renovation of the existing stock.

Off-site construction, with its ability to accelerate construction timelines and create value in territories while reducing nuisances, emerge as an essential element in the construction of the cities of tomorrow. It is an essential tool for local authorities and contractors, enabling them to simultaneously pursue two major ambitions: making the city more pleasant, and rebuilding the city on the city.

TRAINING AND INNOVATION: ESTP COMMITS TO ADVANCING OFF-SITE CONSTRUCTION

The boom in off-site construction is creating considerable training needs at all levels. As a historic leader in the training of construction engineers, ESTP is committed to supporting this transition, convinced of the importance of raising awareness of these emerging dynamics at an early stage.

Thanks to their natural facility with digital tools and their awareness of environmental issues, students joining the school will be the actors of this transition. These new visions and new ways of working, which break with the traditional practices that have long plagued the building world, are the keystone of the construction of tomorrow.

For its part, the ESTP Research Institute supports its partners in their research and innovation efforts, to design the materials, structures, processes and construction systems, as well as digital and methodological tools, needed to overcome the many challenges raised by this transition.

This evolution is at the very heart of ESTP’s identity. Initially founded on a vision focused on the construction of major infrastructure projects, the school now aims to go further by rethinking the city of tomorrow. This is reflected in the evolution of its slogan «l’école des grands projets» («the school of major projects») which has become to «constructeurs d’un nouveau monde» («builders of a new world») this year.