A BER certificate is generally valid for up to 10 years from its date of issue, unless significant changes are made to the home that could affect its energy performance. You may need a new BER assessment after upgrades such as insulation, a heating-system replacement or an extension, particularly if the property is being sold or rented. A registered BER assessor can advise whether a new assessment is appropriate and issue an updated certificate if required. You can check current guidance and assessor details on the official SEAI website.