  Radiative cooling is a passive cooling technology by reflecting sunlight and
emitting radiation in the atmospheric sky window. Although highly desired, full
daytime sub-ambient radiative cooling in commercial-like single-layer
particle-matrix paints is yet to be achieved. In this work, we have
demonstrated full daytime sub-ambient radiative cooling in CaCO3-acrylic paint
by adopting large bandgap fillers, a high particle concentration and a broad
size distribution. Our paint shows the highest solar reflectance of 95.5% among
paints and a high sky-window emissivity of 0.94. Field tests show cooling power
exceeding 37 W/m2 and lower surface temperature more than 1.7C below ambient at
noon. A figure of merit RC is proposed to compare the cooling performance under
different weather conditions. The RC of our cooling paint is 0.62, among the
best radiative cooling performance while offering unprecedented benefits of the
convenient paint form, low cost, and the compatibility with commercial paint
fabrication process.
