Influence and sensitivity evaluation of window thermal parameters variations on economic benefits of insulation materials for building exterior walls-a case study for traditional dwelling in China

The energy consumption intensity of rural buildings in China shows an increasing trend. Adding insulation materials for exterior walls can lower the building energy demand (ED), and evaluating its economic benefits (EB) can provide valuable references for decision-makers. Although many studies have evaluated the EB of wall insulation, the effect of window thermal parameters is rarely discussed. The variations of window thermal parameters can change the ED and the investment cost of the wall insulation, then change the final EB of the wall insulation. In this work, the impacts of four window thermal parameters (U-value, solar heat gain coefficient, window-to-wall ratio, air changes per hour) on the ED and EB of wall insulation are investigated. Then they are ordered according to the global sensitivity analysis results. Meanwhile, the effects of building orientations on these results also be discussed. Results show: (1) The optimum insulation thickness is 50 mm for traditional dwellings when considering the window system; (2) The EB of wall insulation is most sensitive to the air changes per hour, followed by window-to-wall ratio, U-value, and solar heat gain coefficient; meanwhile, the variation of building orientation cannot change this sensitivity order; (3) The insulation costs cannot be balanced out when the air changes per hour exceeds 1.3 h-1 and insulation is not thicker than 5 mm.