Cost-optimal and indoor environmental quality assessment for residential buildings towards EU long-term climate targets

Following the 21st Conference of the Parties (COP 21), the 2015 Paris Agreement on Climae Change strengthens the attempts of the European Union to decarbonize the building sector and to facilitate the transition from fossil fuels towards cleaner energy. The last version of the Energy Performance of Buildings Directive 2018/844/EU is human centric and requires the integration of indoor environmental quality assessment, simultaneously with energy performance and cost-optimal requirements. In other words, efforts to improve the energy efficiency of buildings must actively contribute on reducing the building stock's climate impact while ensuring healthy indoor climate conditions, wellbeing and productivity. This paper introduces the cost-optimal analysis and indoor environmental quality assessment for nearly zero-energy buildings in temperate climate. The study presents several nearly zero-energy buildings (NZEB) scenarios for residential buildings, which include measures that are either upgrades that can be implemented in the as-built case study building or different other configurations of thermal envelope, technical systems and on-site renewable energy production. The cost-optimal analysis results show that among the investigated scenarios, the lowest global cost is achieved by the as-built house, which is an all electric building that has passive house envelope, mechanical ventilation with heat recovery, heat pump and solar collector. Furthermore, the study reveals that with the implementation of PV panels, the primary energy demand can be reduced with 55% at a global cost increase of only 3%. The results and data can be used to compare energy efficincy measures and the related costs between EU Member States.