In the past decade, many tools have been developed to support design decisions related to energy efficient buildings. However, these energy simulation tools are complex and require too detailed input data to be appropriate for use in the sketch design stage. Archi tects and designers hence often take energy related design decisions based on their own experiences or intuition. This paper proposes a simple tool to estimate the energy consumption in the sketch design stage which can, in a later design stage, be linked to a dynamic simulation tool. Furthermore, this study proposes the use of visualisation methods by architects to improve the integration of energy simulations in the sketch design stage. The proposed simple energy estimation tool is based on the “dynamic Equivalent Heating Degree Day Method (dynamic EHDD)”. Relevant sketch design parameters identified are thermal compactness, insulation level, effective use of direct and indirect solar gains, internal gains including occupant presence and activities, and ventilation strategies. In order to develop in-depth simulations, the tool is linked to the dynamic energy simulation software “EnergyPlus” to be used during the detailed design stage. The tool is developed for the Belgian context, but the approach is also valid for other contexts. Keywords: design supporting tool; design process; dynamic EHDD; user behaviour; solar gains; internal heat gain s; energy simulation