Optimisation of the Use of Renewable Energy Sources in Near-zero Energy Building Standards in Poland and in the Czech Republic

European Union member states have, since 2020, introduced a model for the design and construction of buildings to a new energy standard for buildings with near - zero energy demand (nZEB standard). Following European models, many other countries are introducing the nZEB standard as a mandatory standard for building design and construction. Directive 2010/31/EU has left European countries free to adopt the parametric levels of the nZEB standard. The minimum parametric levels characterising the nZEB standard are based on the availability of materials and technology and on the economic calculation that each EU country had to make before adopting the minimum requirements for the nZEB standard. Directive 2010/31/EU only imposed the deadline for the introduction of the nZEB standard as 1.01.2021. A second requirement of the Directive is that renewable energy sources must be used to supply heat, cooling and electricity to buildings as far as possible. However, the percentage of RES sources used in the overall energy balance is not specified. It is not always possible to cover the total energy demand of buildings with renewable energy sources. Often, RES cover only part of a building's energy needs. In this article, the authors analysed the regulations for the nZEB standard in selected countries. Two European countries were selected for further analysis: Poland and the Czech Republic. Using a single - family residential building as an example, an analysis was carried out to determine what percentage of energy should be used from renewable energy sources in addition to other energy sources such as gas, district heating or coal to achieve the near - zero energy building standard defined for the two countries analysed. The analysis carried out by the authors can provide guidelines for the design of buildings to the nZEB standard in both Poland and the Czech Republic.