WUFI

hi
i am trying to modeling one roof (softwood 0.025m/mineral wool(heat cond. 0.04) 0.25m /PA membrane 0.001m) but the problem is that when i set roof composition by WUFI+, the total thermal resistance which have been calculated is 6.528 m2k/w but by WUFI it is 6.48m2k/w.
so would you please tell me about this diffrence???i checked all of material prperties and all of them are same

For the calculation of the total resistance in WUFI Plus the thermal conductivity of the dry material is used. WUFI Pro takes the influence of humid materials into account for the overall R-value calculation.