The housing market is urgently demanding customized quality buildings at affordable costs. Housing prefabrication represents a suitable strategy as long as it is combined with cost-effective personalization through mass customization. Designs need to be easily customizable to foster the mass customization of prefabricated housing. Decisive requirements are design robustness and flexibility. Crucial decisions for the achievement of these requirements are made in the conceptual design phase, but this stage is not adequately supported, and tools for addressing decisions during this phase are not provided. In engineering design, axiomatic design (AD) has been shown to be able to support the analysis of existing ideas in terms of aptitude for customization and the generation of robust and flexible solutions that are easier to customize. Thus, the current study applied AD to the analysis of well-known prefabricated houses and the design development of a new prefabricated housing system to show the potential benefits of this approach for the building industry. Results show that AD has the ability to support the analysis of ideas for identifying problems linked with customization and the ability to address the conceptual development of robust and flexible designs for providing easily customizable solutions.

This research seeks to develop a step change to the way housing is designed for cities in the UK. Housing demand in cities is predicted to increase. Urban centres are struggling to provide affordable housing. Moreover, cities are wasteful in terms of resource consumption, and waste generation heavily affecting the environment. The circular economy offers new ways to design, make and use houses to address these issues systemically as long as technical innovation is combined with social innovation. To date, the circular economy has mainly focused on technical innovation with limited emphasis on user social practices and behaviours. The combination of technological and social innovations through design has just appeared in emerging research and practice areas of design for sustainability. So, approaches that support the design of integrated solutions for transforming large socio-technical systems like cities are not yet well-established. To contribute to the development of integrated approaches for implementing a circular economy in urban housing, this study reviews a set of existing cases of social innovation for regenerative and restorative urban systems. Through empirical observation, we seek to integrate existing theories and concepts on circular economy and formulate theoretical insights for promoting the development of social-technical innovations.

The concepts of “modularity” and “prefabrication” require a deeper understanding being crucial to investigate their relation with the circular economy. Prefabrication involves pre-manufacturing building elements off-site and their transport to the construction site and assembly. Prefabrication can be divided into different categories: Component, Non-volumetric, Volumetric, Modular construction, Hybrid structures, or Whole building prefabrication; and can be based on linear (e.g., columns or pillars), bidimensional (e.g., walls or floor panels), or tri-dimensional elements (e.g., modules or whole prefabricated houses). The most commonly used materials are steel, wood, and concrete, although plastic, composite, and nature-based materials are increasingly being explored. While comparing the prefabricated materials, steel has high embodied impacts but recycle and reuse potential, timber has biogenic content and high reuse potential, and concrete poses transport and assembly challenges. The refurbishment of prefabricated buildings and the use of prefabricated elements in refurbishment are also discussed. The main benefits of adopting prefabrication are impact, cost, material, waste, and time reduction, with quality increase; and the challenges are cultural, technical, and market aspects with some investment required. A bibliometric analysis explores the relationship between modularity, prefabrication, and circular construction and concludes that the link between the three concepts seems fragile and unclear.

The current Italian housing market requires customized high-performance buildings at an affordable cost. Timber building prefabrication represents a suitable way to satisfy this demand, but its application for this purpose is at the moment inadequate mainly due to restrictions of production approaches: the lack of variety of low-cost mass-produced buildings and the high costs of ad-hoc full-customized buildings. In order to provide affordable customized houses, the timber building industry should focus on designs characterized by the combination of mass-produced and customized parts. In this way, clients would have the chance to personalize decisive parts for them, and the building industry can limit costs by the mass production of the others. This strategy involves artefact flexibility and robustness with regard to the architect's viewpoint. Crucial decisions for the achievement of these requirements are made in the conceptual design phase, but in this stage architects’ decision making is not supported by suitable approaches. Axiomatic Design (AD) has been shown to be able to support decision making for the development of concepts that would have the best chance to provide the specified requirements. In this study AD is applied to prefabricated building design in the timber housing industry. Despite limitations placed by timber construction systems, this application results in a prefabricated building system enhanced with regard to robustness and flexibility, and therefore better able to foster designs that satisfy the current housing demand