Passive cooling is based on the transfer of heat by natural means from a building to environmental sinks, such as clear skies, the atmosphere, the ground, and water. The transfer of heat can be by radiation, naturally occurring wind, airflow due to temperature differences, conduction to the ground, or conduction and convection to bodies of water. It is usually up to the designer to select the most appropriate type of technology for each application. The options depend on the climate type.