Optimal roofing solutions for Australian green buildings : a life-cycle cost perspective

Thermal insulation is a significant factor in building construction. As a result, Green Star in Australia requires building envelopes to be insulated properly. Further, green buildings require at least 15% above the required R-values (which are measured in m 2 K/W) for achieving Green Star credit points. Thermal insulation of the roof depends on various factors such as insulation material, sarking material, air films and roof covering. Therefore, there are many options with different combinations available to obtain the required total R-values. This research aims to identify optimum solutions for roofing solutions considering the life-cycle cost. There are ten commonly used roof types in Australia. Therefore, this research calculated the life-cycle costs using the net present value technique for more than 2000 options of roofing solutions and selected optimum solutions for each climate zone in Australia. The outcome shows that the initial cost and the replacement cost significantly influence the life-cycle cost. Further, the maintenance, replacement and disposal costs vary from 47 to 69% of the life-cycle cost. Sensitivity analysis concludes that the discounting rate has a significant influence on the life-cycle cost of the roofing solution. However, the changes in labour rate have only a slight impact on the life-cycle cost of roofing solutions.