A deep retrofit is a whole-home energy upgrade that may combine insulation, windows, ventilation, heating and renewable energy measures to improve the building’s BER. SEAI support can be available through an individual upgrade route or a registered One Stop Shop, but the measures, grant value and eligibility depend on the property and your circumstances. Arrange a professional assessment and confirm the proposed works, costs and likely BER improvement before starting, as grant approval and required paperwork may apply in advance. Check the latest guidance on the official SEAI website and use a registered contractor where required.