The purpose of this Directive is the attainment by Member States of the objective of limiting carbon dioxide emissions by improving energy efficiency, notably by means of drawing up and implementing programmes in the fields specified in article 1, such as energy certification of buildings, the billing of heating, air-conditioning and hot water costs on the basis of actual consumption, third-party financing for energy efficiency investments in the public sector and energy audits of undertakings with high energy consumption. Programmes can include laws, regulations, economic and administrative instruments, information, education and voluntary agreements.