Influence of the ICU phenomenon on the thermal conditions of the indoor environment during hot periods

The concept of comfort, indicating a well-being, is challenging to define in a consensual and objective manner. One approach can be to circumscribe this concept in terms of environmental conditions that are optimal for the execution of a given activity.

Paris region's degraded oceanic climate is characterised by seasonal fluctuations in temperature, with pronounced variations between hot days and cool nights during summer. The classification of this climate as 'moderate' signifies that indoor thermal conditions are deemed to be safe for occupants.

he regulation of the indoor thermal environment is a multifaceted process, encompassing the implementation of external solar protection measures, a function significantly enhanced by the presence of insulation. Additionally, the process entails the nocturnal evacuation of heat through the act of opening windows. The air renewal rate is therefore a key factor in avoiding exposure to heat-related health risks, with wind strength and temperature difference acting as the primary drivers of this rate.

The two parameters are found to be significantly impacted by the urban heat island (UHI) effect in comparison with rural areas, or by the presence of urban parks, contingent upon prevailing atmospheric conditions.

Using observed data on wind speed and temperatures in the city, the consequences of the UHI on the indoor thermal environment are calculated for a dwelling representative of social housing in Paris after renovation.

The sensitivity study on wind and temperature facilitates the identification of conditions under which the UHI significantly undermines the protective function of the building envelope against heat. Furthermore, the impact of the UHI on night-time temperature can be used to adapt ventilation strategies during nocturnal hours, thereby optimising the dissipation of internal heat. Furthermore, the identification of risk factors associated with urban planning, such as distance from vegetated areas or the presence of water (rivers), is enabled.