You only need a BER cert if a property is offered for sale or rent.
No BER cert is needed for lease renewal. I doubt if you need a BER cert for a tenancy renewal with the same tenant (re-registering after four years).
The logic of the BER cert is that a purchaser or tenant should make their decision on a property and how much to pay based on a theoretical cost of heating, lighting and ventilating the property as inspected, just like shopping for white goods.