ISO 15927-4:2005 specifies a method for constructing a reference year of hourly values of appropriate meteorological data suitable for assessing the average annual energy for heating and cooling. Other reference years representing average conditions can be constructed for special purposes. The procedures in this part of ISO 15927-4:2005 are not suitable for constructing extreme or semi-extreme years for simulation of, for example, moisture damage or energy demand in cold years.

Meteorological instrumentation and methods of observation are not covered.