JV3 assessment is a pathway to energy compliance with way more flexibility compared to the rigid Section J DTS pathway. JV3 assessment is a comprehensive modelling approach that covers the building fabric, external glazing and services in a single model (i.e. Proposed Model). This model is then compared to a same model having building fabric and services as required under NCC Section J provisions (i.e. Reference Model). If the proposed model emits less carbon emissions than the reference model, then the proposed building achieves energy compliance. This method allows flexibility to reduce constructions costs or to keep an existing low-performing gas boiler. We do this by offsetting the loss of energy via better insulation elsewhere or installing solar PV, etc. (which is not possible under DTS pathway).