Thermal performance for buildings has come a long way. Initial emphasis was on energy simulation with greenhouse gas reduction being primary driver. Modern building simulation suites offer analysis of natural ventilation, detailed HVAC modeling, cooling load estimation, daylighting analysis, visualisation of sun paths and sun penetration within spaces, and CFD analysis for air flow and temperature at specific time periods within a single GUI. DesignBuilder is such a system, allowing such analysis to be carried out within a short time frame. The lecture will cover above aspects and provide example of it's use in real projects.