Assessment of life cycle embodied energy and material cost in Australian shopping centres: Implications for material selection

Abstract

Shopping centres are the fastest-growing retail space in Australia driven principally by population growth and urban sprawl. A shopping centre undergoes frequent renovations and refurbishments during its life cycle for several reasons. These can include the need to increase foot traffic, improve sales and fixed term leasing periods of retail spaces. The refurbishment frequency of retail shops in shopping centres is exceptional compared to other commercial property assets, with refurbishments every 2 to 10 years. Consequently, building materials in shopping centres experience premature replacements due to economic, functional and social obsolescence. This overexploitation of resources ultimately increases the embodied energy and greenhouse gas emissions in shopping centres. Yet despite this, there is a lack of knowledge on embodied environmental impact of shopping centres in Australia, which constitutes a significant obstacle in achieving improved sustainability.

This thesis presents assessments of embodied energy and GHG emissions of shopping centres by developing an object-oriented model with three case study applications. Subregional shopping centres were selected as cases because they represent the largest share of shopping centre floor space (planned and existing) in Australia.

The embodied environmental effects of a building are predominantly governed by the materials and assemblies employed in its structure, envelope, and finishes. To minimise embodied effects, it is essential to select building materials with better environmental performances, which might increase life cycle cost. Hence, the object-oriented model prioritises both embodied energy and material cost to identify viable material and assembly solutions.

The model assessed and compared 8,820 assembly combinations across 16 different shop types in selected shopping centres. Results demonstrate that the estimated life cycle embodied energy and material cost of a typical single-storey subregional shopping centre are estimated to be around 485 TJ and AU$ 38 million as of 2019, respectively. Recurrent embodied energy is 45% of the total embodied energy, leading to an annual value of 193.15 MJ/m2, which is significantly higher in comparison to other building assets. The largest contributing shop type for life cycle embodied energy and material cost is the centre structure. Results reveal that informed use of current building materials and assemblies (i.e. engineered timber structures, fly ash cement in concrete, cork and other timber based products) significantly reduce embodied energy and emissions (up to 43%) and deliver material cost savings (up to 17%) in comparison to the business as usual scenario. The introduction of a carbon tax is also identified as an effective mechanism to encourage the selection of materials yielding a reduction of embodied energy and GHG emissions. The research outcomes demonstrate that the premature replacements of building materials and assemblies in shopping centres have a significant effect on their embodied energy demand and this varies significantly by shop types.

The contributions of this study will allow building designers and other project participants to evaluate material selection decisions while enabling policy makers to develop regulations and guidelines that compel or encourage the selection of materials and assemblies with improved environmental performances. This research contributes to mitigating adverse environmental effects of the built environment.