New regulations concerning new and existing residential buildings took effect on 1 January 2008. All new buildings and existing buildings undergoing significant renovation must meet new energy performance requirements. The regulations introduced a calculation method for measuring energy performance. New buildings must be accompanied by an energy performance certificate. For existing buildings, an energy performance certificate is required in case of change in the buildings owner or tenant, as well as if significant renovation is undertaken. The certificate provides a rating of the buildings energy performance, as well as advice on improvements that can be made. Only certified architects, engineers and experts can issue the certificates. The Ministry of Economy and Foreign Trade, along with Luxembourg's Energy Agency, provide specialised training for professionals on energy performance certification.