NZEB renovation definition in a heating dominated climate: Case study of Poland

Abstract

The main objective of this article is to propose possible requirements for NZEB (nearly zero-energy buildings) renovation definition in heating dominated climate. A survey was carried out on potential approaches and indicators that could be used for the NZEB definition of existing single-family houses in Poland. The process of determining requirements for the NZEB renovation definition was divided into two stages. The cost-optimal U-values of the building's envelope were initially calculated and, based on them, the energy demand for heating (QH) and the reduction of non-renewable primary energy demand (QP) were estimated. The calculations were made for different energy prices, locations, and two building models. Based on them the requirements for cost-optimal renovation (QH ≤ 60 kWh/(m2 year), QP reduction ≥ 75%) and NZEB renovation (QH ≤ 40 kWh/(m2 year), QP reduction ≥ 80%) were proposed. In contrast to definitions using only a maximum level of QP, two indicators were used. Such a solution is appropriate for existing buildings because it prevents the situation in which only renewable energy sources (RES) (with a low primary energy factor) will be applied in order to decrease the primary, non-renewable energy demand.