A circular approach to facade design

The built environment has a significant impact on our natural environment, depleting non-renewable resources, overwhelming landfill sites, and contributing to substantial greenhouse gas emissions.

The European Commission estimates that the construction industry is responsible for ~50% of all extracted raw materials and 35% of all total waste generation. Operational energy consumption from buildings accounts for ~36% of total GHG emissions and another 10% is attributed to embodied carbon associated with material manufacturing. As the construction industry, we must move away from the existing ‘take, use, dispose’ mentality and as building envelope decision makers it is our responsibility to take on this challenge.

Sustainability in the context of building envelope design has primarily focused on optimising operational design and comfort, specifying U-value and G-values for optimal thermal and optical performance (among other performance parameters). As we head towards a catastrophic environmental tipping point, we must shift to examine our role as a building envelope industry more holistically and consider environmental impacts beyond the service life of the facade alone.

The following paper proposes a circular approach to building envelope design and introduces three circular performance indicators to assess façade materials and products: lifecycle resource consumption, lifecycle waste generation and lifecycle carbon emissions.

A traditional unitised curtain wall system is used as a test case to quantify the current industry environmental impact. The critical materials of the tested system: aluminium, and mineral wool, are assessed in detail to evaluate the impact of varying production processes (i.e extruded, cast and rolled aluminium, annealed, heat-treated and laminated glass) and finishes (i.e milled, anodised and powder coated aluminium, performance coated and fritted glass). The assessment considers regional factors to provide an international comparison.

An industry review of circular material alternatives (i.e low carbon, or recycled materials) is undertaken for comparison. The alternatives are substituted into the unitised curtain wall test case to assess any improvements in the circular performance indicators.

The barriers, risks and opportunities of the circular approach are discussed, including economic and regulatory hurdles. The impact of closed loop recycling and renewable resources on the overall reduction of lifecycle carbon is highlighted. The paper concludes with recommendations for benchmark targets and how the building envelope industry can support the shift towards holistic façade sustainability.