Since 2019 and 2021 energy performance of nearly zero energy level is required from new residential and non-residential buildings by Energy Performance of Buildings Directive (EPBD). Currently, building sector consumes large 40 % share of the final energy usage. Pressures for energy saving efforts are created by legislation induced by proceeding climate change, national economies and healthy indoor climate. Growth rate of residential building sector is 1 % in many European countries. The modern-age buildings constructed in the period 1991-2010 form only 14-19 % of the entire housing stock. Although new buildings have lower energy consumption levels in comparison to old ones they may also have higher electricity use due to increased need for ventilation, cooling, lighting and office equipment. By quality assurance process, commissioning, the intended performance of new building is aimed to confirm before the operation phase. Optimal operation of mechanical, electrical and HVAC systems generate additional energy saving options for new buildings. The common aim is to produce best possible indoor climate with least amount of energy.