Building envelope systems for the circular economy; Evaluation parameters, current performance and key challenges

The building industry is the world's largest consumer of raw materials. In an effort to reduce the rate of consumption there is an urgent need to adopt more efficient recycling and reuse practices in the building industry. Emerging to support this need is the circular economy framework (circularity) – a concept that aims to separate ‘economic growth from environmental destruction’. Using the framework of circularity this research critically evaluates the ‘reuse’ performance of a key area of modern construction; the external envelope layers of timber framed buildings. The research collates circular assessment criteria relevant to the evaluation of building envelope layers from literature. In conjunction with real-world deconstruction tests and the aforementioned circularity assessment criteria the study identifies two key trends limiting circularity in the building envelope; the widespread presence of fixings that irreversibly damage components, and the widespread use of chemically modified materials (i.e treated and/or engineered timber). Given the prevalence of such building methods in New Zealand, Australia and North America there is a clear need for research that proposes fixing and material technologies for building envelopes that meet circular economy design criteria.