Following the EPBD, an EPC shall include the energy performance of a building and the reference values, as well as the recommendations for the cost-optimal or cost-effective improvements of the energy performance of a building or building unit. Within the national context, it is up to the Member States to decide on the performance rating of the representation (i.e. energy level vs. continuous scale) as well as the type of recommendations (i.e. standardised vs. tailor-made). The majority of countries applied the energy label scale, typically from A to D-G. Some Member States also decided to introduce additional parameters in the scope of the EPC, such as the percentage of energy from renewable sources, heat losses, solar gains or comfort and air quality issues.