Optimisation of retrofit wall insulation: An Irish case study

Ireland has one of the highest rates of emissions per capita in the world and its residential sector is responsible for approximately 10% of total national CO2 emissions. Therefore, reducing the CO2 emissions in this sector will play a decisive role in achieving EU targets of reducing emissions by 40% by 2030. To better inform decisions regarding retrofit of the existing building stock, this study proposes Optimum Insulation Thicknesses (OIT) for typical walls in 25 regions in Ireland. The calculation of OIT includes annual heat energy expenditure, CO2 emissions, and material payback period. The approach taken is based on Heating Degree Day (HDD) and life cycle cost analysis methods for different combinations of insulation material, heat energy type, and Irish wall configuration. Results indicate that OIT increases with increased HDD and varies up to 30% from lower to higher HDD regions in Ireland. The type of wall materials, configuration, insulation type, and heat energy type all have a significant impact on annual cost saving potential (up to 170 €/m2) and carbon emission (up to 50 kg/m2). The Analysis of Variance (ANOVA) technique is used to compare the significant mean difference between combinations under OIT and cost savings.