nZEB ( Nearly Zero Energy Building standard) is the European Energy Performance of Buildings Directive Recast 2010 (EPBD). It requires all new buildings to be nearly Zero Energy Buildings (nZEB) by 31st December 2020 and all buildings acquired by public bodies by 31st December 2018. This standard is now being applied to all relevant building designs and requires buildings designers and owners to achieve 20% of their primary energy needs from renewable sources on site or nearby. Callaghan Engineering have undertaken nZEB design on 5 school projects over the past 3 months to bring the already completed designs up to the required Part L of the building regulations 2017 for buildings other than dwellings. Central to the design process is the development of a new thermal model to test that with improved design elements for insulation u-values, airtightness, thermal bridging, glazing and using 10% renewable energy contribution we are achieving the necessary reduction in energy demand compared to a similar building prior to nZEB (reference building). With the design teams , Callaghan Engineering achieved the necessary nZEB changes through the use of photovoltaic cells on the roof and improved u-values in walls, glazing, floors and roof.