European policies on the reduction of primary energy consumption of existing buildings, in earthquake-prone countries, often clash with inadequate structural performances. To prevent increased losses from renovated buildings, it is important to combine energy retrofit measures (ERMs) with seismic retrofit measures (SRMs). To select the best combination among ERMs and SRMs, existing criteria often do not consider a proper life-cycle perspective, i.e., the present value of costs (PVC) and its differential value (DPVC) of the alternative in comparison to the present state. This article proposes a multiple-criteria decision rule for ranking combined ERMs and SRMs, which accounts for improvements buildings’ energy and seismic performance, as well as related costs, and test the decision rule on a 20-th century masonry building. The earthquake losses (EL) and capacity to demand ratios for each SRM were obtained for a predefined time span, through individual interventions (e.g., grouting) or combined (e.g., grouting and stiffening of the roof slab). The most common ERMs were chosen, enabling to meet the performance levels prescribed by the Italian codes, individually (e.g., external thermal insulation) or in a combined way (e.g., external thermal insulation and replacement of doors and windows). By considering a 30-year period, firstly, investment costs, maintenance costs, energy cost, and expected seismic losses were estimated separately and then summed to obtain the PVC and DPVC of combined ERMs and SRMs. The most cost-effective ERMs involve using external thermal insulation, while SRMs often increased the PVC compared to the present state and only some of the combined retrofit measures turned out to be profitable investments. Overall, energy costs represent the 25% of the alternatives’ PVC and the seismic ones the 40%. The decision rule for selecting the best option considers the normalized variations of energy consumption (En), seismic performance (Sn) and DPVC (Cn) for each combined retrofit measure, graphically represented by a 3D scatterplot. The better alternatives are those which are closer to the line En=Sn=Cn. According to our findings, in our setting, the better options are those combining envelope insulation with grout injections. The proposed decision rule is both simple and flexible, as the angle of the line can be adjusted based on the relative importance assigned to the three criteria considered.
Proposal of a multicriteria decision rule to select combined structural and energy retrofit measures
Luca Sbrogio';Chiara D’Alpaos;Maria Rosa Valluzzi
2024
Abstract
European policies on the reduction of primary energy consumption of existing buildings, in earthquake-prone countries, often clash with inadequate structural performances. To prevent increased losses from renovated buildings, it is important to combine energy retrofit measures (ERMs) with seismic retrofit measures (SRMs). To select the best combination among ERMs and SRMs, existing criteria often do not consider a proper life-cycle perspective, i.e., the present value of costs (PVC) and its differential value (DPVC) of the alternative in comparison to the present state. This article proposes a multiple-criteria decision rule for ranking combined ERMs and SRMs, which accounts for improvements buildings’ energy and seismic performance, as well as related costs, and test the decision rule on a 20-th century masonry building. The earthquake losses (EL) and capacity to demand ratios for each SRM were obtained for a predefined time span, through individual interventions (e.g., grouting) or combined (e.g., grouting and stiffening of the roof slab). The most common ERMs were chosen, enabling to meet the performance levels prescribed by the Italian codes, individually (e.g., external thermal insulation) or in a combined way (e.g., external thermal insulation and replacement of doors and windows). By considering a 30-year period, firstly, investment costs, maintenance costs, energy cost, and expected seismic losses were estimated separately and then summed to obtain the PVC and DPVC of combined ERMs and SRMs. The most cost-effective ERMs involve using external thermal insulation, while SRMs often increased the PVC compared to the present state and only some of the combined retrofit measures turned out to be profitable investments. Overall, energy costs represent the 25% of the alternatives’ PVC and the seismic ones the 40%. The decision rule for selecting the best option considers the normalized variations of energy consumption (En), seismic performance (Sn) and DPVC (Cn) for each combined retrofit measure, graphically represented by a 3D scatterplot. The better alternatives are those which are closer to the line En=Sn=Cn. According to our findings, in our setting, the better options are those combining envelope insulation with grout injections. The proposed decision rule is both simple and flexible, as the angle of the line can be adjusted based on the relative importance assigned to the three criteria considered.Pubblicazioni consigliate
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