Dr. Tricia Keilthy:

It might involve a gradual phasing out of BER F or G-rated properties such that one would have to upgrade them in the first instance before reaching the C grade. Reaching the C grade would be quite a leap in the case of a lot of rental properties. The shallower measures such as attic and cavity wall insulation can help in some ways and are not as costly as deeper retrofits which should be prioritised in the case of local authority housing.