Early design phase energy predictions using a semi-dynamic approach as an accurate proxy for dynamic energy simulations

[Display omitted] •New algorithm for accurate prediction of operational energy in early design phase.•Extension of static “equivalent degree day method” into dynamic method.•Intuitive visual representation of parameters affecting dynamic degree days•Prediction of environmental impacts without additional inputs.•Automatic generation and visualisation of design space. The building sector is well known as one of the significant contributors to climate change. The use of materials and energy are important drivers, both during construction and the whole life cycle. This study is part of a research to improve the Belgian national approach of life cycle environmental assessment for buildings. The current approach focusses mainly on material use, and the operational energy is estimated via the equivalent degree day method assuming a fixed value of 1200 equivalent heating degree days per year. This paper extends this widespread degree day approach to improve its accuracy by including the effect of various parameters (climate, building characteristics, obstructions by the environment, occupant behaviour). Step by step user-friendly input and graphical feedback is moreover considered necessary for designers and has been added. The annual heating energy estimated by our proposed semi-dynamic model has been validated by dynamic energy simulations using EnergyPlus of 8000 randomly generated cases. Both results have been plotted in a 2D graph. The slope of the linear regression through the origin is 0.8955, and the R-square value is 0.9058. Based on this comparison, it is concluded that the semi-dynamic model, with simplified input and fast results, has sufficient accuracy for the first design phases compared to the dynamic model.