ZEMCH 2015 - International Conference Proceedings | Page 88

In this study, the more variation around regression line points out higher influence of the specific parameter in output uncertainty. Input ranking is determined by considering this equation: Dominance factor (%)=1-R2 (2) As seen in figure.7, uncertainty in Rp, either solely in the left side or included in combination set of input parameters in the right side represents the highest output uncertainty effect; while other parameters have rather equal position in the graph. This result denotes that among investigated input parameters, geographical based disparity in product prices might cause the greatest uncertainty in global cost calculation outcome. Figure 7: Dominance ranking of input parameters in output uncertainty; (a) left: individual parameters, (b) right: combination set of parameters. Conclusion This study investigated stochastic nature of some input parameters involved in cost optimal nZEB calculations and their effects on output uncertainty. By conducting an uncertainty analysis, obtained results of Monte Carlo simulations represented a normal distribution and revealed the probability that potential output be located within ±5% of base case value (deterministic calculation) is 68% while it is 95% for ±10% around it. In sensitivity analysis, through the regression analysis carried out, it was observed that Rp (product price development rate) has the highest dominance in affecting output uncertainty and created the largest variance; while other studied parameters were at the same level of importance. Therefore, for higher level of accuracy in results, more precise input assumptions are required. For this purpose, it is desired that EU suggested methodologies in their following revisions consider stochastic nature of input parameters in determination of cost-optimal nZEB level and include them as a phase in calculation process. This could be achieved through a parametric procedure which in preliminary steps marginal error of each uncertain input parameter is determined and all values