A survey on prototype and currently commercial dynamically-tintable windows has been performed. The technologies of electrochromic, gasochromic, liquid-crystal and electrophoretic or suspended-particle devices were compared and validated for daylight and solar energy control in buildings. State-of-the art commercial electrochromic windows seem most promising to reduce cooling loads and lighting energy in buildings, where they have been found most reliable and able to modulate the transmittance by up to 68 percent of the total solar spectrum. Their efficiency has already been proven in hot Californian climates, but more research is necessary to validate the products for colder climates, and to improve furthermore the commercial products in order to control the indoor climate in a more energy efficient way by reducing both heating and cooling loads.status: publishe