Will naturally ventilated dwellings still be safe under heatwaves?

Heatwaves are often responsible for many deaths due to high temperature indoors. Energy savings is a key element in building design and refurbishment works to reduce the impact of climate change. Natural ventilation is often promoted as an indoor space cooling solution thanks to its energy saving potential.
The paper deals with prediction of heat-related health risks situations in naturally ventilated dwellings.
In these spaces, indoor thermal conditions depend on windows opening and on difference between outdoor and indoor temperatures. The efficiency of temperature control also depends on especially building thermal inertia, solar gains and occupants’ behaviour. Yet, meteorological variability and occupants’ behaviour are difficult to predict. Thus, operating limits of technical solutions using natural ventilation are not totally reliable because of uncertainties on the variability of these parameters.
In order to decrease uncertainties in prediction of heat-related health risks and to secure building design, the first step of a science-based methodology is proposed to help building sector professionals. It links consensual indicators, including ergonomics of the thermal environment standards, to distinguish between a moderately warm situation from heat stress causing unhealthy indoor environment for occupants. Simulations are performed for a dwelling with different air flow rates under contrasting meteorological conditions to illustrate the methodology and the potential limits of natural ventilative cooling, according to health risks.
In tested dwelling, natural ventilation can reduce indoor temperature but doubt remains about providing comfortable conditions. According to ergonomics standards scopes, a gap occurs between "moderate thermal environment" and "heat stress" areas. Further investigations are needed to bridge the observed gap.