5. Embodied Energy Existing Frame Cast concrete= 1.3MJ/kg 6000 tonnes= 7,800,000 MJ 7,800,000 MJ= 2,166 Mwh Existing + Replacement Frame= say 4,300 Mwh Estimated heating requirement for new building: 68 Mwh per annum Energy saved by retaining existing frame would heat the building for 63 years