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Passive Cooling

Cooling that needs no electricity — how reflective and radiative materials protect people, buildings and ecosystems from extreme heat.

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Key terms in this topic

Passive Cooling
Cooling a surface, building or space using materials and design instead of electricity.
Passive Daytime Radiative CoolingPDRC
A material that stays cooler than the air even under direct sunlight by radiating heat to the cold sky.
Reflective Cooling
Cooling by bouncing sunlight away from a surface before it can be absorbed as heat.
Radiative Cooling
Heat loss from any object by emitting thermal infrared radiation.
Cool Roofs (Reflective Roofs)Reflective Roofs
Roofs coated or built with high-reflectance materials so buildings absorb far less heat.
Reflective Canopies
Overhead structures with a reflective upper surface that shade people and land beneath.
Reflective Reservoir Systems
Covering water reservoirs with reflective floating panels to cut evaporation and cool the surroundings.
Albedo
The fraction of sunlight a surface reflects — 0 is black, 1 is a perfect mirror.
Solar Reflectance
The fraction of incoming solar energy a surface reflects across the sun's spectrum.
Thermal Emittance
How efficiently a surface releases heat as infrared radiation.
Atmospheric WindowSky Window
A band of infrared wavelengths (roughly 8–13 μm) where Earth's atmosphere is nearly transparent to heat.