A BER rating is improved by reducing the calculated energy demand of the home, most effectively through better insulation, upgraded windows and doors, an efficient heating system such as a heat pump, and adding renewable technologies like solar panels. The most cost-effective combination of upgrades depends on the specific building, so a BER assessor's advisory report or a SEAI-registered one-stop-shop can help prioritise measures.
A BER is calculated using the DEAP methodology, which models a home's fabric, heating system, ventilation and renewable energy contribution to estimate its energy use and carbon emissions. Improving the rating means reducing that calculated demand, and the biggest gains typically come from addressing the building fabric first: attic and wall insulation, draught-proofing, and upgrading old single-glazed windows and doors, since heat loss through an poorly insulated fabric is usually the largest factor in an older Irish home's poor rating.
Heating system efficiency is the next major factor. Replacing an old oil or gas boiler with a heat pump, alongside sufficient insulation to make a heat pump effective, can produce a substantial jump in rating, as can improving controls such as zoned heating and better thermostats. Adding renewable technologies, particularly solar photovoltaic panels, also contributes positively to the calculation by offsetting a portion of the home's electricity demand.
Because every home is different, the most effective and cost-efficient sequence of upgrades varies: a poorly insulated older home usually benefits most from fabric improvements before a heat pump is installed, while a newer, well-insulated home might see the best return from renewables or heating controls. A BER assessor's advisory report, issued alongside the certificate, sets out property-specific recommendations, and SEAI's home energy upgrade schemes can help identify a logical, grant-supported sequence of works.