Energy savings potential and life cycle costs of deep energy retrofits in buildings with and without habitable style loft attic conversions: A case study of Irelands residential sector

This paper evaluated the potential energy and life cycle cost (LCC) savings arising from the deep energy retrofit of residential buildings. The cost optimal model was determined for material upgrades and the addition of an air-to-water heat pump, where the household level of savings at 2023 energy prices will be dependent on the typical housing characteristics and weather conditions. LCC savings post retrofit for a detached dwelling insulated at the ceiling/rafter including installation of a heat pump amount to a €20,031-€21,370 for an uninsulated dwelling pre-retrofit, rising to €38,448 for dwellings with a habitable loft conversion. Partially insulated dwellings, pre-retrofit did not all incur favourable returns in investment, and in some cases were unviable. Although, the application of a 50% grant results in a viable return on investment for home owners. A sensitivity analysis found high discount rates, fuel prices and increasing capital costs can negate positive returns on investment. Finally, at a national level energy saving of 7.72 TWh by 2030 could be realised if the Irish Climate Action Plan 2023 retrofit targets are adhered to. In addition, total LCC savings could be valued at €1.4 billion. Where only material upgrade are pursued a loss occurs of €0.56 billion.