Cool roofs stay near ambient temperatures even on the hottest summer days. Cool roofs are defined by the radiative properties known as solar reflectance and thermal emittance. The energy and cost efficiency achieved when cool roofs are applied depend upon the initial roofing construction, the climatic conditions, the type of cool roofs applied and their specifications. In order to evaluate the energy performance for cool roofs’ application in the EU region the web based Cool Roofs toolkit was developed. The main specifications of the specific toolkit are user friendliness, accessibility and maximum possible accuracy. Annual cooling and heating loads are calculated based on degree day method and then are regulated to include internal gains. The calculations for the evaluation of energy savings are adopted by the DOE cool roofs calculator and adapted to the EU climatic conditions.