An improved Trombe wall is proposed to adapt to building construction with selective thermo-insulation facades (internal and cavity wall insulation, but not external wall insulation system). The case study is conducted in Xining, Capital city of Qinghai province in China, where the general building facades are mostly selective thermo-insulation facades to fight against the severe cold. A numerical analysis is undertaken to show the effects on the improvement of the building’s thermal environment by comparing the improved Trombe wall system with the classical Trombe wall system. The operating efficiency of the improved Trombe wall can be up to 33.85%, an increase of 56%. The results show that the improved Trombe wall works more effectively than the classical Trombe wall system in utilizing solar energy for the sample building.