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/

Prefabrication experiments - 473 - Héliobulle : A «sunlight sphere»

 

Reducing negative environmental impacts and conceiving energy-positive construction systems has never been as important considering the drastic and catastrophic effects of climate change that are visibly modifying our collective landscapes. Prefab has generally been linked to more economical, and energy efficient systems articulated to replicable component fabrication and assembly which curtail construction waste. In previous eras of crises, building system inventors have coupled some of prefab’s advantages with mechanical and natural biophilic conceptions in symbiotic relationship toward complete energetic autonomy. 

 

An architecture of energy systems was best represented by Buckminster Fuller's Wichita house and geodesic dome houses within unfamiliar shapes and geometries made pertinent through their potential for resource efficiency.

 

Fuller's ideas inspired many other experiments, one which is particularly characteristic of the era's zeitgeist. The Héliobulle or geodesic «light-sphere» proposed and patented by architects J. and M. Pattou combined a spherical dwelling with an energy production machine. The icosahedron prototype deployed 20 outstretched triangles in a 3-frequency grid assembled from 180 triangular reinforced and plastic faces. South facing surfaces included solar absorbing elements which channeled power through a central vertical tube connected to a stocking chamber underneath the living floor. In cross-section, five adjustable posts attached to reinforced concrete cylinders cast onsite supported the levitating orb. A wind turbine connected to the central tube served as a complement to the solar energy production. 

 

Mandated by the French Alpine Club, the 6-meter diameter tiny mountain bivouac huts included a furnished ground floor area for living and a loft for sleeping.  The patent describes the sphere as the perfect solar shape; the sun’s rays would always reach at least one of the composing triangular faces perpendicularly at a particular time of the day. Each polyester based monocoque triangle was designed as a layering of either absorbing, undulating, or transparent material depending on its position on the sphere in relation to the sun’s trajectory. Assembled in just ten hours by four people this geodesic sphere certainly expresses its ties to Buckminster fuller's theories of maximum livable space within a minimal lightweight building kit.

Architects' representation of the «Helio-sphere»

 

Prefabrication experiments - 472 - A Perfect Storm for Mass Timber

 

Selected materials and construction strategies embody the era they are invented in. Pozzolanic ash concrete provided Roman builders with an artificial stone to erect vaulted and domed structures that still stand today. Industrialization harnessed new energies for steel and concrete elevating construction capacity for edifices of scopes, sizes and heights impossible to imagine before then. Reinforced concrete, a robust and intrinsically fire-proof material, came to represent the modern industrialized housing block. Casting this malleable and resistant material into shapes reformed onsite construction as surface elements for floors, walls, roofs, and other required components like stairs or balconies could be precast in quantities offsite, delivered and easily assembled onsite. The precast large panel blocks of postwar France epitomize the marriage of a material's properties and overwhelming demand for its use. 

 

Today, critical decarbonization of building activities to reduce construction’s environmental footprint, increasing urbanization and a demand for quickly built housing is stimulating the demand for another twentieth century material:  engineered laminated timber. Both glulam and cross laminated timber are embraced as eco-friendly as their low carbon footprint when compared to energy intensive materials like steel or concrete has unveiled a competitive edge in the age of rapidly evolving climate change. 

 

Engineered laminated mass timber is relatively simple to produce, and components can be fashioned in any geometry and precisely cut as customizable offsite produced kits for building. Parts, slabs, panels, columns can also be normalized or standardized according to spans and dimensional requirements of reproducible building types. The Sylva scalable timber construction system by European forestry company Stora Enso demonstrates the straightforward mass timber approach: post and beam glulam is complemented by cross-laminated elements for bearing or spanning elements. Along with their school kit, Stora Enso produces components ranging from simple linear elements to comprehensive modular volumetric building sub-assemblies to be stacked into multiple configurations. Along with sequestering carbon during their lifespan, if the timber is protected adequately and its joinery designed for disassembly, components can be deployed over multiple lifecycles, making mass timber perfect for low embodied energy building.

School ConstructionComponents by Store Enso

Préfabrication experiments - 471 - From assembly lines to trucks, ships, trains and helicopters

Manufactured dwellings are idealized for efficiently supplying homes delivered from a factory to any site. Mobile homes built on standard-sized steel trailers were designed, robustly built to be pulled over roads and adapted to common towing devices. Modular volumetric buildings use similar manufacturing principles, without the mobile substructure, and require flatbeds to carry the volumes to their site, where they are lifted to be set into their final position. Cranes equipped with spreader beams, used to strap the modules, make easy work of modular assembly. Both approaches, a steel mobile trailer or an independent volume, are defined and constrained by transport loads and dimensional parameters.

 

Getting these factory-produced buildings to remote locations sometimes requires more complex logistics; Cargo ships can be used for intercontinental transport. Stacked on ships, they can be rolled off or craned onto barges to be brought to ports and then trucked to their final destinations. Rail is also possible, however it is considered less convenient as the modules would have to be lugged to and from rail lines as manufacturing facilities are not necessarily located in proximity to railway networks. 

 

Another form of modular transportation has been imagined to get houses to any location. While impractical, complex and expensive, the dream of flying a house is connoted in many prefab experiments. But is it really feasible ? High-capacity helicopters, such as the Sikorsky S-64 Skycrane, Boeing CH-47 Chinook, and the Russian Mil Mi-26, are known for their exceptional lifting capacities. These helicopters are specifically designed for lifting and carrying loads exceeding 20,000 pounds (9,072 kilograms). A standard modular volume 12feet x 40feet can easily weigh up to 20 000 pounds. While lifting and delivering one unit is certainly possible, assembling a building in this way is unfeasible. 

 

Whether truck, rail, ship or helicopter, modular volumetric construction is regulated by its factory manufacturing on an assembly line which also determins maximum width as in all cases the module will have to be trucked from its production area to a staging area before its final transport. 

Sikorsky S-64 Skycrane (above); Boeing CH-47 Chinook (below)

Prefabrication experiments - 470 - Soft densification and pre-approvals

 

Industrialization has certainly sped up production of every commodity and reduced their cost per unit. In an era of urgency, housing promoters were inspired by advances in manufacturing. In the wake of World War 2, the subsequent population growth and economic boom of the «Trente Glorieuses», suburbanization and development were linked to the automobile’s democratization. Bedroom communities planned with small uniform houses sprouted using assembly line principles. Along with housing, strip malls, and schools deployed similar modular planning methods in a generalized sprawl of mass-produced built form. 

 

Vast building initiatives consumed resources and quickly reorganized the live-work relationship around commuting. The current climate crisis reframes postwar suburbanization's dwelling provision strategies as wasteful and is providing a context for these bedroom communities to be reimagined as land reserves for soft densification in response to the need for affordable housing. As was the case in the first act of suburban building, communities are again turning to industrialization to quickly provide replicable housing types. To skip over some of the time-consuming permitting and planning associated with one-off projects, catalogues of preapproved designs that add-on, retrofit, or provide accessory units on existing tracts are an attempt to increase housing supply and curtail uncontrolled sprawl.

  

The town of Collingwood in Ontario, Canada has initiated a streamlined ADU (accessory dwelling unit) permitting process based on pre-approved designs, financial incentives, and landlord support tools for ADUs marketed as rental units. ADU’s can be delivered to backyards, attached to an existing structure, or included within the main dwelling unit. The designs are intended to ease design decisions and procurement. One of the preapproved designs is a a 516 sq feet modular volumetric unit, a design by Habitat 28 and Attimo Homes, engineered-to-order and delivered to any site circumventing the usual permit process. A streamlined procurement timeline includes client, permit department, fabricator and builder; this type of integrated supply chain of actors can certainly decrease housing supply challenges using industrialized building systems geared toward repurposing underutilized land resources.

Plan of the P50 by Habitat28 and Attimo Homes

Prefabrication experiments - 469 - Platform theory for scaling efficiencies

 

The current affordable housing crisis is driving policies for change in the construction industry and its supply chain sectors. Necessary steps toward efficiencies include reducing bureaucracy, increasing productivity and performance; Performance framed by climate change, requires low-carbon building solutions while increasing supply. Factory production using materials and methods that harmonize quality, quantity along with reducing construction's wastefulness and environmental footprint is promoted within the future of construction road maps toward decarbonization in many countries.  

 

Manufacturing principles can be deployed to increase efficiencies and have proven their worth in all industries with building construction lagging. Industrialized building has had some successful applications in architecture; modern timber, steel and concrete construction systems were directed to solve the housing crises of the interwar and postwar years. 

 

Timber framing used in tract housing, most notably in Levittowns, is a case in point where sawn lumber was dimensioned consistently and deployed to an incredible number of houses using similar spans, plans, and elements. Dimensional consistency within a well-established and understood supply chain is what made timber framing so scalable. The same type of scalable normalization was used in steel buildings for large hangars or storage facilities. Panelized reinforced concrete also used material normalization to become a formidable, industrialized building system in Europe. All three construction methods can be described as «platforms» geared to particular types; small spanning timber for houses, large-spanning steel for industrial buildings and fireproof concrete for multiunit buildings. 

 

Still, the one-off nature of the construction industry impedes the scalable standardization in supply chains required by manufacturing.  Industrial production applied to building calls for a comprehensive transformation toward an integrated process with platform theory at its core. Using the same platform - type relationship that led to the above-mentioned successes in processes and designs should be directed toward consistency in building design and production. Further cross-sector collaboration between manufacturers should be based on normalization to share challenges and offer opportunities for best practices to be streamlined throughout the industry. This would allow one-off singular projects to be based on repeatable details, components and manufactured elements - developing a mass-customizable approach in construction. 

Top left: Levittown mass production; bottom left: Typical concrete panel block; Right: a platform for combining residential spaces into diversified designs (Resolution 4 architecture)

Prefabrication experiments - 468 - Flexibility of on and offsite reinforced concrete

Whether cast on or offsite, reinforced concrete construction was generalized for collective housing in a relatively short period between the end of the 19th and the middle of the 20th century. Prized for its rapidity, strength, flexibility and fireproofing, the malleable material also sustained the invention of new industrialized building systems and their architectural potentials. Slabs and columns could take rationalized form-resistant shapes and heights difficult to achieve in conventional timber or masonry construction. Further, the open plans based on a rigorous grid of distanced posts or columns generated horizontal arrangement fields free from the structural constraints of customary bearing walls. Massive postwar rebuilds throughout Europe contributed to understanding the possibilities for these systems to be mass-produced and modulated for any context. 

 

In Italy during the late 1960s and early 1970s many collective housing blocks were erected by fostering the advantages of reinforced concrete with precast elements. Italian architect / designer, Angelo Mangiarotti planned a series of collective dwelling blocks which showcase the shared knowledge maturing in multiple countries. Born on February 16, 1921 in Milan, Mangiarotti graduated in architecture from the Milan Polytechnic in 1948. He met modern masters Frank Lloyd Wright, Walter Gropius, Mies van der Rohe and Konrad Wachsmann as a visiting professor at the Illinois Institute of Technology in Chicago in the early 1950s, where prefabrication was extensively seen as the future of architecture and construction. 

 

After returning to Italy, Mangiarotti founded a studio, and investigated a building system that combined onsite cast concrete flat slabs with a modular precast curtain wall system hung from the perimeter of the concrete floors. Based on a strict modular grid, factory-made opaque or transparent vertical panels would simply slide and suspend from a horizontal modular lintel block anchored to the main structural slabs. A compositional interplay of vertical panels and windows varied the arrangement according to any customizable layout within the adaptable open plan. This hybrid onsite and offsite system was stacked to 8 stories at Monza from 1968-1975 and 5 stories in Arosio contributing to the rebuilding of Italy and defining the country as a locus for the study of flexible open prefabrication.

Edge detail of the suspended curtain wall