For that you just need to make sure your emissivity is low below the black body wavelength at the temperature it should have at night. This is already in use/te

For that you just need to make sure your emissivity is low below the black body wavelength at the temperature it should have at night. This is already in use/testing to serve as a kind of A/C in some locations, but iirc. it requires a clear sky to dump the heat into space.