Optimum insulation thickness determination of a building wall using exergetic life cycle assessment

To minimize the building energy consumption and its environmental impacts using effective insulation material is a vital task. This study performs an optimization of insulation thickness in a building wall based on a new method named exergetic life cycle assessment which combines the exergy analysis and life cycle assessment. The environmental impacts associated to the insulation materials among with the fuel used for compensation of exergy loss from the room are considered as the objectives for minimization. Also, a life cycle cost analysis takes the insulation material and fuel into account for cost minimization. Two insulation materials are used in the analysis named Rockwool and Glasswool. The optimal thicknesses, which are calculated based on environmental impact analysis, are 0.219 m and 0.098 m for Glasswool and Rockwool, respectively with net saving of exergetic environmental impact equal to 215.8996 mPts/m2 and 161.2979 mPts/m2. The optimum insulation thickness based on exergetic life cycle cost analysis are found to be 0.018 m and 0.012 for Glasswool and Rockwool, respectively with annual cost saving of 1.6028 $/m2 and 0.7658 $/m2. A sensitivity analysis reveals that total exergetic environmental impact is affected by temperature of the fuel entering the combustion chamber, the temperature of stack gasses and combustion temperature. The walls with lower thicknesses, through the use of optimum insulation thickness, higher amounts of net savings and lower payback periods could be obtained.