Potential of mechanical ventilation for reducing overheating risks in retrofitted Danish apartment buildings from the period 1850-1890 – A simulation-based study

Advancing energy efficient renovation solutions in buildings necessitate adopting high-insulation and airtightness to avoid heat loss through transmission and infiltration, which can result in overheating. Elevated indoor temperatures have a highly negative effect on building occupants’ health, wellbeing and productivity. With the possibility of remote working, people spend more time at home, and therefore addressing the elevated indoor temperatures and the overheating risks in residential buildings proves to be essential. Even more so, as these high temperatures during daytime are followed by consequent high temperatures during night-time, which distorts sleep quality. The current Danish building regulations suggest that the operative temperature in dwellings should not exceed 27 °C for more than 100 hours per year and 28 °C for more than 25 hours per year. However, in many new and renovated dwellings in Denmark the temperature during spring and summer exceeds these measures. The paper presents the first results from a larger study focused on typical Danish apartment buildings from the period 1850-1950 many of which currently undergo extensive renovation. The main objective of the project is to study facade solutions that eliminate overheating. The present paper reports an effect of different ventilation strategies on overheating in renovated apartment buildings from the period 1850-1890. The investigation showed that energy renovation in this type of buildings, including adding insulation and exchanging windows, yielded energy saving of approx. 60%, but resulted in an increase of overheating hours when no mechanical ventilation system was added. All studied mechanical ventilation systems with heat recovery were able to decrease the overheating hours below limit specified by the Danish building code in the case of the building situated in the narrow street canyon. In the absence of shading from surrounding buildings, the CAV ventilation operating with minimum airflow required by the Danish building code reduced overheating hours insufficiently.