Passive cooling for the built environment

Passive cooling technologies reduce heat and solar gains in buildings and public spaces while dissipating excess heat. This approach could reduce impacts of mechanical air conditioning, which has environmental impacts and consumes electricity, contributing to peak demand and grid stress. In this Review, we discuss advances in passive cooling technologies, focusing on smart solar control, ventilation, and radiative, evaporative and hybrid dissipation systems. These technologies are at different stages of development and deployment, ranging from technologically mature approaches such as ventilative cooling and solar control to emerging materials for passive and radiative cooling. Each technology has benefits and trade-offs. Ventilative, radiative and evaporative cooling have low energy use, but their effectiveness is dependent on climate, timing and air quality. Solar control improves thermal comfort, requires maintenance or has design constraints. Implementation of these technologies can reduce cooling-related energy consumption and provide thermal comfort in communities where access to affordable cooling is limited. However, increasing temperatures and humidity changes could challenge their effectiveness. Policies are needed to encourage uptake of passive cooling approaches in communities that currently rely on mechanical cooling and enable uptake for those that lack cooling access.