Prefabrication experiments - 477 - Prefab as policy

 

Catalogued designs, uniform platforms, replicable buildings, preapproved prefab micro dwellings - governments are scrambling to test many of these ideas to supplement affordable housing supply faced with a stagnating construction sector. Offsite construction complements these approaches by applying manufacturing methodologies to increase efficiencies and capacity. While some see current crises as prefab's heyday, the possible links between manufacturing, architecture and housing construction already sustained modernism a century ago. 

 

Modern architects explored and elevated prefab to a type of language spawned through material innovation, redirecting architectural production from the onsite fashioning of materials to the streamlined assembly of factory-made components. From relationships with military industrial complexes, governments also underwrote prefabrication as a way forward toward stimulating inventive systems. Prefab’s time came and went in the 1940s, 50s and 60s with each generation explaining why their era was the right time for a robust turn toward industrializing construction.

 

Going from architecture and construction as a cultural phenomenon based on centuries of onsite informalities and peculiarities to industrial production tainted by mass production connotations is a transformation that requires more than simple reforms - it requires a complete conversion of business models for builders that are ingrained in business-as-usual and apprehensive about the expanded economic risks that go along with mass production. These changes are even more tenuous as demand for and successful application of offsite construction as a product-based pattern is constrained to certain relevant building types with repeating organisations. 

 

Iconic experiments like the Lustron House, designed by Carl Strandlund, convey the rich heritage of government support along with ambitious inventors looking to produce coordinated components for easy-to-assemble low-cost housing. Their application was largely obstructed by onsite principles promoted by tract housing developers like William J. Levitt who took simple to build platform or balloon framing and democratized onsite mass production processes that were ingrained with complete flexibility.  Lessons from both production methods tell the tale of prefab's marginal uptake and consumers' enduring need to feel that their home is a one-off process, even though all its components and properties are mass-produced.

Onsite construction using mass production principles

Prefabrication experiments - 476 - Carbon emissions onsite versus offsite

 

Prefabrication, industrialized building systems and offsite construction are valued for their potential to reduce costs, condense timelines and to bolster quality standards. As tasks are transferred into factory and manufacturing settings, the effective harmonized workflows that are applied in other industries bring added value to the preassembly of large building fragments to facilitate on site coordination. Still marginally applied when compared to conventional construction methods, the climate crisis along with housing and labour shortages have put prefabrication on policy makers' radar to address many current challenges. 

 

Among present drivers for innovation in prefabrication is the need to decarbonize the built environment, reducing embodied carbon of materials and methods along with infrastructures' operational carbon. Offsite manufacturing has the potential to reduce waste at every step of the fabrication process; this argues for its systematic use even though comprehensive studies demonstrating relative reduction in embodied carbon are lacking and offer contradicting viewpoints. Component fabrication reduces embodied carbon by optimizing material use, however in some cases, as in modular volumetric construction, embodied carbon can be slightly higher due to material redundancy.

 

Holistic, whole building studies are complex and require methodologies that account for the immense variety of materials, components, contexts, seasonal variables, climate conditions and processes involved in building construction. It can be simple enough to calculate embodied carbon of site cast concrete versus offsite cast panels; however they only account for a specific element within the building’s overall footprint.

 

All seem to agree that offsite construction’s shorter schedules, in part due to task overlapping logically lead to lower carbon emissions; if the construction of a building is reduced by 3 months over a 12-month schedule, time savings translate to less travel to and from sites for everything from workers, tooling and machinery. Further, projects that are built in extreme conditions require heating. Propane or any other type of energy is squandered as buildings' temporary enclosures offer little climate performance. Onsite's wastefulness is well-documented which can easily be mitigated with offsite construction. 

Carbon emissions from buildings - diagram by lmnarchitects.com 

 

Prefabrication experiments - 475 - Modular evolutions in mass timber

From forest to sawmill, to artisans and finally to the construction site, timber buildings evoke a modesty linked to generations of builders. Dry joinery, steel anchors, bolts and a plethora of other fasteners, including the earliest iron cut nail, have made it possible to create both grand and vernacular structures. Recent advantages in engineered timber products complement enduring principles to elevate timber's advantages without some of the dimensional nuisances, distortions and changes associated with sawn lumber.

 

Glulam and cross laminated timber (CLT) in particular have become synonymous with a type of precise kit-of-parts construction where elements are shaped to sizes as well as complex profiles and assembled to generate variable forms with the robust technical characteristics generally associated with steel or reinforced concrete, but without the carbon footprint of these energy intensive materials.

The kit-of-parts approach to timber construction based on digital manufacturing of detailed building components reduces waste by optimizing offsite methodologies and delivering only necessary elements to site. Further, mass manufacturable and scalable with a high strength to weight ratio, cross laminated timber is being deployed in projects as a potential alternative to concrete flat slab systems common to fireproof multistory buildings. 

 

Staging the mass customization and adaptability potentials of CLT, Nordic Structures, a Canadian producer and supplier recently produced modular volumetric CLT boxes in the Northern community of Chibougamau, Québec located approximately 500 km north of Montréal. Les Pavillons du 49° designed by Montreal-based studio Perch architects was fostered by Nordic's local vertical supply chain, from forest to panel to module to delivery, to erect this first example of modular volumetric CLT in the company's portfolio. It only took four days to stack the 47 factory produced modules. A total of 20 rental units, each organized from at least two CLT mega chunks delivered with exterior cladding, leaving weatherproofing and stitching to be finalized on site. Large balconies along with dynamic window placement were used strategically as arrangements to avoid the modular box type architecture sometimes associated with modular volumetric. 

Nordic Structures, Les pavillons du 49° during module setting and construction

Prefabrication experiments - 474 - Organized offsite pre-assembly with Consolidation Centres

 

Building construction dictates logistic challenges: closing streets off to traffic, delivering materials and oversized machinery to sites, and disposing unused or hazardous materials are just a few elements that underscore the intricacies associated with even the most accessible sites. These complications are exponentially augmented in remote locations with extreme climate conditions where construction is limited to certain seasons. 

 

Beyond the habitual obstacles faced in accessible communities, the housing supply crisis in remote areas like the Far North is compounded by sociodemographic barriers including years of underfunding, a tenuous grasp of local housing demand and building culture, sizeable distances between communities, and rapidly changing climatic conditions accelerated by global warming.  Further, construction’s highly fragmented design to delivery process is aggravated by difficult to reach sites impeding the normative, quick, effective and sustainable supply of housing. Prefabricated houses have been proposed to solve some of these issues, however the logistical challenges of onsite delivery and completion along with low social acceptability of shipping less than adapted housing exacerbates the already problematic context. 

 

An issue that should be addressed is the convoluted delocalized supply chains disconnected from local settings and onsite assembly in communities without existing production infrastructure.  Construction Consolidation Centres (CCCs) are increasingly researched and explored to harmonize the just-in-time delivery of components to complex building contexts. A combination of management, logistical and distribution facilities receive orders for components and materials which can be assembled into large modular building chunks or optimally packaged as kits-of-parts to reduce onsite time or waste and ensure efficient resource management. 

 

Governance of these CCCs for remote construction would have the potential to link multiple communities, achieve economies of scale, and prepare optimal housing bundles into ready-to-deliver loads.  A co-op CCC operated by neighbouring communities enables coordination of diverse physical and social needs. Beyond the grounded harmonization of actors, CCCs require a political will combined with policy tuning supply with delivery, along with pertinent design, inspection and operation criteria for quality products.  The CCC model combined with offsite preassembly can be a way forward for reducing the entanglement of actors, methods, materials and components associated with conventional supply models. 

Construction Consolidation Centre imagined by CSB Logistics - https://www.csblogistics.com/