Cooling energy demand in Danish residential buildings under climate change: simulation of naturally-ventilated options

Rising temperatures in Europe are increasing the need for sustainable cooling in buildings. This aspect requires building simulations to be performed under updated weather conditions to ensure proper sizing and optimization of HVAC systems operation. To address this challenge, this paper analyses the cooling demand of eleven monitored apartments in Copenhagen. The analysis of 2023 summer data shows that conditions of thermal discomfort arose in the units where windows’ opening was overlooked. Each dwelling is modelled as a lumped-capacitance network integrating natural ventilation modelling. Dynamic simulations are run to calculate the apartments sensible cooling demand under different setpoints (26 °C, 25 °C, 24 °C), weather scenarios (summer 2023, Test Reference Year, projected datasets for 2050 and 2090) and HVAC system management. The outcomes highlight a sensible cooling demand up to 20 kWh/m2 with 26 °C setpoint for units characterised by large glazed surfaces when windows are closed. By exploiting natural ventilation, the demand can be reduced by 65–95 % compared to the fully closed-window scenario. Comparable cooling needs are observed for the 2023 and 2050 scenarios, while a decrease is seen in 2090 due to lower predicted solar irradiance. Conversely, the cooling loads are underestimated adopting the Test Reference Year. The combined operation of natural ventilation and active cooling systems lowers the demand compared to the separated use, although peak loads remain similar. The results stress that HVAC systems in Danish buildings should be adapted to changing climatic conditions, but a rational usage of natural ventilation could mitigate the increasing cooling demand.