Passive solar and natural cooling: Impact on the biosphere
Protecting people in heatwaves without heating the planet
What this tab covers Effects on human, animal, plant, fungal and microbial life and on whole ecosystems: in the short term (construction and early years), medium term (operating life) and long term (decommissioning and legacy).Passive design is mostly beneficial: it avoids the electricity and refrigerant emissions of air conditioning and protects people from heat. Space cooling uses about 2,200 TWh a year and causes about 1 Gt of CO2. Specific risks are limited to water use and seawater-cooling discharge.
World electricity for space cooling about 2,200 TWh a year2 CO2 from cooling electricity about 1 Gt a year (about 3% of global emissions)2 Share of US building primary energy used for air conditioning nearly 15%4Effects over time
| Life affected | Short term | Medium term | Long term |
|---|---|---|---|
| Humans2 | Little evidence of harm beyond normal building risks. | Cooler interiors without electricity protect health in heatwaves; about 700 million more people could live in hot climates by 2050, and over 40% of people in hot climates may still lack cooling then. | Buildings designed for passive comfort keep working when power supply fails. |
| Animals5 | Little evidence of effect. | Seawater cooling returns deep water to the sea; South Pacific experience suggests marine life and coral reefs can thrive near outlets. | Little evidence of effect. |
| Plants2 | Little evidence of effect. | Planted trees are used for shading in passive cooling. | Little evidence of effect. |
| Fungi and soil life2 | Little evidence of effect. | Little evidence of effect. | Little evidence of effect. |
| Ecosystems2 | Little evidence of effect. | Avoided cooling electricity cuts power-sector emissions; refrigerant leakage from air conditioners adds about another 1 Gt CO2e a year. | With better design and efficient equipment, 2050 cooling demand could be about 1,200 TWh instead of up to 5,000 TWh. |
How the effects are reduced
The main risk is a design wrong for the climate: unshaded glazing overheats, and evaporative coolers waste water in humid regions. Climate-specific building codes, shading and auto-flush rather than continuous bleed-off address these. Seawater systems need assessment of the outlet so that returned water does not harm reefs.
Sources
- Buildings Decarbonisation Report: Summary, Cooling Energy Transitions Commission, 2025
- Passive radiative cooling below ambient air temperature under direct sunlight (Raman, Anoma, Zhu, Rephaeli and Fan, Nature 515, 540-544) Nature, 2014
- Sustainable cooling: a deep dive into seawater air-conditioning solutions for the Caribbean World Bank Blogs, 2024