Some banks insist on you having a BER Cert before you can even apply for a mortgage. Also most banks now offer Green Mortgages for homes that have a BER of B3 and above, which is another attractive incentive for homeowners to invest in energy upgrades. Bank of Ireland are currently offering a sliding scale discount on all homes with an energy rating from A to G, which means the better the BER rating of your home, the bigger the discount you will receive on your mortgage rate. See details on their EcoSaver mortgage here.