When sourcing roof insulation coatings, prioritize the Solar Reflectance Index (SRI); a high SRI (typically >100) indicates superior heat rejection. Additionally, verify the thermal conductivity (K-value) to ensure it meets your energy-saving targets. For durability, ensure the coating has an elongation rate of at least 200-300% to accommodate the thermal expansion and contraction of the roof without cracking. Lastly, check the adhesion strength (measured in MPa) to ensure it is compatible with your specific substrate, whether it be metal, concrete, or bitumen.