Abstract The building envelope is a key factor affecting the energy efficiency of buildings. Often, building envelope design requires both explicit knowledge and tacit knowledge. In practice, the tacit knowledge embedded in existing envelope design cases is significantly underused. To enhance the application of such knowledge, this paper proposes a case-based reasoning (CBR) model for the decision support of building envelop design during the preliminary design stage. A case library of 100 certificated green public and commercial buildings is used to develop the model. An experiment on a test case is performed to verify the methodology and usability of the model. Furthermore, records for 25 certificated green public buildings are used to validate the effectiveness of the model. The result shows that the accuracy rate of the CBR model is 84% when considering heating and cooling demands of envelopes. In conclusion, the proposed CBR model is promising for improving the efficiency of envelope design for public and commercial buildings while reducing the reliance on expert participation.