You apply by hiring an SEAI-registered BER assessor, rather than submitting the application directly to SEAI. The assessor inspects the property, records details such as its construction, insulation, heating and ventilation, and may ask for plans, receipts or information about upgrades. They then calculate the rating and lodge the BER on the national register, usually providing a BER certificate and advisory report. Costs and the final rating vary by property and assessor, so check the SEAI register and confirm the requirements before booking; the assessor is responsible for the official assessment.