Development of an Offsite Construction Typology: A Delphi Study

Offsite construction (OSC) delivers multiple products that vary in design and building complexity. Considering the growing prevalence of OSC, a systematic categorization of OSC types can offer operational and macroeconomic benefits to the construction industry. The purpose of this study is to develop an OSC typology through a systematic process, as existing studies do not present a rigorously evaluated typology that suits the modern OSC context. The research addresses the following research question: what are the distinct characteristics of unique OSC types that have emerged through the adoption of Industry 4.0-based technological advancements? Due to the rapid advancement of production and construction technologies, the existing OSC classifications are becoming outdated. As such, a detailed review of OSC technologies was conducted which enabled the identification of OSC categories: components, panels, pods, modules, complete buildings, and flat-pack (foldable structure). A series of case studies was then reviewed to explore and analyze the relevance of these OSC types in practice. It was then subjected to a Delphi-based multi-level expert forum to develop a modern and future-proof OSC typology. The rigorous process validated, defined, and delineated the boundaries between the OSC types. The research confirmed that OSC types can be broadly categorized as volumetric (pods, modules, complete buildings) and non-volumetric (components, panels, foldable structure). The results indicated that OSC skills vary with the complexity of OSC types, and that lightweight steel and timber are the most common materials.

Thermal Performance Improvement of Double-Pane Lightweight Steel Framed Walls Using Thermal Break Strips and Reflective Foils

The reduction of unwanted heat losses across the buildings’ envelope is very relevant to increase energy efficiency and achieve the decarbonization goals for the building stock. Two major heat transfer mechanisms across the building envelope are conduction and radiation, being this last one very important whenever there is an air cavity. In this work, the use of aerogel thermal break (TB) strips and aluminium reflective (AR) foils are experimentally assessed to evaluate the thermal performance improvement of double-pane lightweight steel-framed (LSF) walls. The face-to-face thermal resistances were measured under laboratory-controlled conditions for sixteen LSF wall configurations. The reliability of the measurements was double-checked making use of a homogeneous XPS single panel, as well as several non-homogeneous double-pane LSF walls. The measurements allowed us to conclude that the effectiveness of the AR foil is greater than the aerogel TB strips. In fact, using an AR foil inside the air cavity of double-pane LSF walls is much more effective than using aerogel TB strips along the steel flange, since only one AR foil (inner or outer) provides a similar thermal resistance increase than two aerogel TB strips, i.e., around +0.47 m2∙K/W (+19%). However, the use of two AR foils, instead of a single one, is not effective, since the relative thermal resistance increase is only about +0.04 m2∙K/W (+2%).