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Civil engineering, Construction engineering
Despite the importance of addressing the challenges of the 2020 emissions reduction targets of both the European Union (EU) and Ireland, current residential emissions policies have focused mainly on the few existing studies that are primarily used to predict end-use energy and CO2 emissions savings. To allow all energy and emissions across life cycle phases to be evaluated, a process-based life cycle analysis (LCA) hybrid model was developed with the aim of determining the extent of reductions in resource consumption, greenhouse gas (GHG) emissions and costs of maintaining the existing Irish housing stock.
Thirteen representative archetypes of the pre-1960 – 2002 existing housing stock were developed, and the impacts of each archetype assessed across life cycle phases to give a ‘BaseCase’ for energy and emissions. Two scenarios for upgrading the housing stock model were analysed – ‘meet current building regulations’ (Building Regulations standard) and 'meet anticipated future regulations' (Passive House standard i.e. a house that has its operational energy demand as low as practically achievable). This involved identifying and modelling a range of interventions which achieved energy ratings equivalent to the Irish 2010 building regulations and Passive House standards, respectively. These upgraded stock models were then reassessed to estimate their impacts on energy and emissions. Cost evaluations were also carried out for the differing archetype upgrades.
For all archetypes in the BaseCase scenario, results show that operational phase energy and emissions are much greater than for any other phase, representing at least 95.5% in a majority of archetypes. 13% of the life cycle’s energy consumption was estimated to come from non-Irish sources. For a majority of archetypes, the weighted average archetype embodied energy was estimated to be approximately 0.5% of the life cycle energy out of which 29% was estimated as embodied energy due to services (i.e. installation of materials and fit-outs). All retrofit scenarios yield significant operational improvement: primary energy reduced for a majority of dwellings, compared to the BaseCase scenario.
It is estimated that a total of 76MtCO2-eq and 104.2MtCO2-eq national life cycle emissions savings compared to 2005 levels can be achieved at positive retrofitting abatement costs of €592/tCO2-eq and €741/tCO2-eq in 2020 for the Current Regulations and Passive House scenarios, respectively. A comparison between Current regulations and Passive House scenarios indicated that a total of 21.2MtCO2-eq national emissions savings compared to 2005 levels can be achieved at retrofitting abatement costs of €1,141/tCO2-eq in 2020. Detached houses in the Passive House scenario in year 2020 is a good choice for energy efficiency improvement as they represent the highest GHG abatement potential that can be delivered at relatively lowest costs, especially when it is considered that they become more cost effective overtime. This is followed by mid-terraced houses/apartments. Semi-detached houses/end-terraced houses display the lowest GHG abatement at highest retrofitting costs. The effective implementation of this choice will require a combination of regulation, financial support and information/education.
Famuyibo, Albert Adesoji.(2012) Reducing life cycle impacts of the existing Irish housing stock".Doctoral Thesis, Dublin Institute of Technology. doi:10.21427/D7QC8J