Life cycle cost analysis for determining optimal insulation thickness in Palestinian buildings

This research performs an optimization of insulation thickness in buildings external walls based on a Life Cycle Costing (LCC) approach. Buildings sector consumes 43% of total Palestinian energy. Although building insulation is a low investment with guaranteed benefits alternative, it is still elective in Palestine. Eight governorates were considered in the analysis. The analysis takes into consideration typical external walls construction, insulation types, weather data, energy prices, heating and cooling equipment conversion efficiencies, and market financial parameters. Two types of insulation were studied which are polystyrene (denoted by I1) and polyurethane (denoted by I2). For energy type, electricity is assumed for summer cooling and LPG fuel for winter heating. Optimal insulation thicknesses were calculated assuming different Degree Days (DD) base temperatures T-b. Results show that insulation type and DD have the highest significant effect on optimal insulation thickness. Polystyrene (I1) and Polyurethane (I2) investment costs are 83 and 171.43 $/m(3), respectively. Despite that, same optimum financial benefits can be achieved using (I2) at half thickness compared to (I1). For all cases, optimal thickness varied between 0.4 and 9 cm. At T-b equals to 18 degrees C, annual savings varied between 4 and 8 $/m(2)/year. Simple Payback Period (SPBP) analysis values varied between 0.9 and 1.6 years. This research is the first to analyze effects of buildings insulation on annual heating and cooling loads in Palestine. The authors believe that it should motivate decision makers to develop a Palestinian building code that considers building insulation a mandatory item. Fortunately, this research proved that it is financially attractive.