Analysis on life-cycle costing for insulated external walls in Australia

Thermal insulation is one of the integral parts of building construction. Further, it is also a significant factor in achieving energy efficiency. Therefore, minimum standards are set up for thermal insulation in buildings. Further, to achieve energy efficiency of green buildings, it is required to achieve higher thermal insulation standards. The external wall being the outer skin of the building covering a considerable proportion of the building envelope, needs to be properly thermally insulated. However, there is a clear lack of research on the different types of insulation options for external walls regarding life-cycle perspective. Therefore, this research aims to develop and analyse life cycle costs for seven different types of external wall structures commonly used in Australia. Life cycle costs are calculated using net present value (NPV) technique for various types of insulation material, sarking material and different types of external wall structures in the five main cities in Australia. A sensitivity analysis is also carried out for the changes in discounting rate and for the changes in labour rates. According to the life-cycle costs analysis, the maintenance cost of the external walls varies from 13% to 29% and the costs of demolition range from 13% to 25% of life-cycle costs. Clay masonry veneer and reverse veneer external wall solutions could achieve the required minimum R-values in all climatic zones with a lower life-cycle cost. Further, life cycle cost increases with the increment of the total R-value of the external wall structure. Cost other than the initial cost varies from 34% to 45% in external walls The results derived in this research can be used to make informed decisions on insulation material selection for green buildings.