Disclosed is a method to produce composite materials, which contain customized mixes of nano- and/or micro-particles with tailored electromagnetic spectral properties, structural elements based thereon, in particular layers, but also bulk materials including inhomogeneous bulk materials. In some embodiments the IR-reflectivity is enhanced predominantly independently of reflectivity for visible wavelength. The enhanced IR-reflectivity is achieved by combining spectral properties from a plurality of nano- and/or micro-particles of distinct size distribution, shape distribution, chemical composition, crystal structure, and crystallinity distribution. This enables to approximate desired target spectra better than know solutions, which comprise only a single type of particles and/or an uncontrolled natural size distribution. Furthermore disclosed are methods of manufacturing such materials, including ceramics, clay, and concrete, as well as applications related to design and construction of buildings or other confined spaces.