Chapter 5 of the Health Effects of Climate Change (HECC) in the UK: 2023 report. This chapter highlights several key insights for public health. Measures to mitigate climate change such as passive or low-carbon heating and cooling, energy-efficient lighting, and solar energy will enable existing homes to become more energy efficient, may help alleviate fuel poverty and improve thermal comfort in winter. However, such measures also increase building airtightness and without accompanying improvements in ventilation, retrofitted homes may experience degraded indoor environmental quality. Overheating in summer is associated with adverse physical and psychological health impacts. The effects of exposure to noise from mechanical ventilation are not yet understood; however, the ingress of environmental noise from transport has adverse psychological and physiological impacts on health, such as sleep disturbance and cardiovascular and metabolic diseases.