This article extends a novel advanced dynamic calculation method (IDEAS - Inverse Dynamics based Energy Analysis and Simulation) of assessing the controllability of a building and its servicing systems. IDEAS allows confident (i.e. calibrated in SAP) predictions to be made regarding the impact of novel heating and renewable energy systems. IDEAS can be used as a dynamic sizing tool for a heating system in a building and can be used to benchmark control systems performance as it can represent near perfect control. The addition of an air source heat pump model to IDEAS is described. This allows for detailed analysis to be made of air source heat pumps in a SAP-compliant framework, taking into account the dynamic nature of the system efficiency and thermal capacity