A research team in Stanford University designed new panel that can cool structures even under direct sunlight. This panel is made of nanophotonic materials and has a maximum reflectance keeping the building from heating, therefore it reflects as much of sunlight as possible and also it achieves minimal absorption throughout the solar spectrum. From an engineering standpoint the building must radiate heat back into the space as much as possible; as a result this will reduce the heat transferred into the interior spaces of the building. When this panel accepts the incident solar energy, it changes the frequency band to be less transparent to the atmosphere and it radiates it more efficiently that from a normal black body spectrum.
The new panel achieves both goals, it is an effective reflector for solar light and it also emits thermal radiation very effectively. According to the research, the new panel is capable of saving 100 watts per square meter and their study give an example of a typical one – story, single house with just 10% of its roof covered by radiative cooling panels could offset 35% its entire air conditioning needs during the hottest hours of the summer. Although, it is too early to predict how successful these panels are in the market and how competitive are compared with the other products.
Some materials that have similar properties: silver teflon radiator coating material, “gold” thermal blanket and black thermal blanket
This picture is for spacecraft covered with the golden blanket. However, I do not think someone will use it to cover the building and save some energy.