Rules of thumb for energy-efficient renovation of apartment buildings : The case of Nils Holgersson, the Swedish statistical home

Abstract: In Sweden, there are around 300 000 multi-family buildings with high energy consumption state a high renovation potential in the building sector. This study aims to analyze different renovation measures for a typical theoretical multi-family building to determine their effects on energy consumption, financial profitability, and impacts on obtaining an energy label in the rating system. The reference building was created based on the given energy consumption for the Nils Holgersson building (NH), where the information data accumulated and assessed utilizing dynamic energy simulation software IDA ICE.The selected renovation measures include modifications to the building envelope and ventilation. The reference building was equipped with an exhaust ventilationsystem with no heat recovery. The study showed that heat losses through ventilation contributed to the largest share. The losses through windows and walls are significant; hence selecting ventilated façade and adding insulation were relevant efficiency measures. The study analysis a vacuum insulation panel (VIP) applied for external walls due to its highly efficient thermal properties compared to conventional insulation. The results of life cycle cost analyses (LCCA) for 40 years demonstrated that VIP and ventilated façade have an economic benefit because of the energy cost saving during the operation phase of the building, despite the high initial cost. The cumulative LCC for each measure showed that VIP approaching the conventional insulation within theservice life the ventilated façade is cost-efficient at the end of the 6thyear compared to changing glazing. The selected rating system is Miljöbyggnad (MB). After renovation, the NH building could achieve the bronze level on the energy indicators.The study found that the energy consumption in the base model was 144.7 kWh/m2and the implemented renovation package leads to a reduction of 47 % annual heating demand. As a rule of thumb, the annual energy demand will be 90 kWh/m2, and the cost for the renovation package including installation would be 1150 SEK/m2causing a total energy-saving 2900 SEK/m2at the end of 40 years.