The philosophy behind EN15251: Indoor environmental criteria for design and calculation of energy performance of buildings

European Directive for Energy Performance of Buildings (EPBD) was approved in the beginning of 2003. The transition period is 3–6 years depending on the article. European Standardisation Organisation (CEN) has drafted several standards to help the member countries implementing the directive. One of these is the “indoor environmental input parameters for design and assessment of energy performance of buildings-addressing indoor air quality, thermal environment, lighting and acoustics”. The standard specifies design values of indoor environment, values to be used in energy calculations, and methods how to verify the specified indoor environment in the buildings. The standard includes methods for long-term evaluation of the indoor environment. The paper describes the philosophy and some of the principles used in the standard, and gives examples presented in the standard. A draft standard has been under the international review process and has now been finnally approved at the formal vote.