A review of HVAC solution-sets and energy performace of nearly zero-energy multi-story apartment buildings in Nordic climates by statistical analysis of environmental performance certificates and literature review

Multi-story apartment buildings, also known as multi-family or multi-unit residential buildings, represent the largest share of newly constructed, residential floor area in Norway, Sweden and Finland. Since the start of 2021, these buildings are required to be nearly-zero-energy under the Energy Performance of Buildings Directive. However, there has been limited research into defining solution-sets to achieve these requirements. This study utilises the detailed databases of Energy Performance Certificates (EPCs) of the three countries to analyse solutions used in low-energy buildings built in the last 20 years. This was supplemented by exemplar projects and literature presenting novel solutions. Resulting low-energy solution-sets involved district heating or heat pumps (primarily ground source) to provide hydronic heating and domestic hot water. A secondary source (often direct electric) was commonly used to cover peak load. The dominant ventilation strategy was balanced ventilation with high efficiency heat recovery. An alternative, found in a minority of Swedish projects, was an exhaust air system integrating a heat pump. A single optimum solution-set could not be defined due to differences between regulations and climates. The different primary energy factors used in each country had a significant effect on the preferred solution. Further study is required to determine if these factors affect a country's entire building stock or just the EPC grade a building achieves, skewing the statistical results.