Analysis and optimization of external venetian blind shading for nearly zero-energy buildings in different climate regions of China.

• Effect of external venetian blind on nearly zero-energy buildings was studied. • Energy performance of external shading in different climate regions was quantified. • Multiple optimization design of shading arrangement parameters was discussed. • A new index was proposed for evaluating the energy efficiency of external shading. The development and promotion of nearly zero-energy buildings (NZEBs) is an inevitable trend of building energy conservation, and external venetian blind shading (EVBS) is one of the most effective technologies for NZEBs. Therefore, this study aims to analyze and optimize the energy-saving performance of EVBS for NZEBs in different climate regions of China. Based on EnergyPlus, the optimal shading arrangements of NZEBs are obtained by evaluating the shading performance of different shading slat angles, orientations, window-to-wall ratios (WWRs) and locations. The results show that the energy saving potential of EVBS for NZEBs is significant, especially in southwest of China. And the energy-saving trends of EVBS with different shading arrangements are similar regardless of the climates, and the maximum energy saving potential per unit window area of EVBS is obtained in slat angle of 0°, west orientation and low WWR. The total energy saving potential (P) gradually decreases first and then increases rapidly as the slat angle increases for all slat angle (0°~180°) shading conditions. And the multi-orientation shading effect is the sum of each single-orientation shading effect. In addition, the cooling efficiency index (CEI) is proposed to evaluate the importance of shading to reduce the cooling demand of buildings, and to guide the improvement of the self-performance of shading. This research will be helpful in guiding the application of EVBS for residential NZEBs in different climate regions of China. [ABSTRACT FROM AUTHOR]