Integrated operational and life-cycle modelling of energy, carbon and cost for building façades

The buildings sector contributes 20% of global greenhouse gas emissions, and building energy use is anticipated to double by 2050. Building performance research has typically focused on the operational phase, with life-cycle impacts increasingly studied, but often in isolation. This paper presents a novel framework integrating building energy modelling with life-cycle analysis and life-cycle costing. This is applied to four façade glazing materials in a 15-story case study office building in Queensland, Australia – a sub-tropical and commercial example rare in literature but important for future building development. Results demonstrate that double-glazed low-emissivity material (Type 4) was the most energy and financially efficient despite higher embodied energy and carbon than alternatives. It yielded operational energy and greenhouse gas emission savings of 13% against the baseline, and 2% lifetime financial savings. Clear double-glazing (Type 3) had the poorest overall performance, attributed to its low U-value trapping heat within the building and increasing net energy and emissions. This was new evidence that clear double-glazing should be carefully considered in sub-tropical climates. The integrated approach identified a material with improved overall performance. If only embodied impacts (production, transport, disposal) were assessed, GT1 would appear the best option as it takes less energy and carbon to manufacture and transport yet has very poor operational performance. This paper extends existing knowledge on façade materials and will aid future work on sustainable, low-emission building design in other climates, economies, designs and industries.