Bizi zikloaren ikuspegitik eraikinen birgaitze energetikoen prozesuen analisi teknoekonomikoa

Based on the new energy performance limitations determinate by the Directive 2010/31/EU, the buildings become more energy efficient and the impact of the operational stages is reduced, increasing the relevance of the environmental and economic impact of the other life cycle stages. In addition, the energy refurbishment requirements are increasing, generating the need to integrate the life cycle methodology during the prioritization process between the different energy-efficient retrofitting strategies for buildings. However, despite the Life Cycle methodology has already been standardized, as buildings are extremely complex systems, a lot of studies usually apply some simplifications to reduce the time of the evaluation. Based on these simplifications and seeing that when talking about the energy renovation of an existing building, the main objective is focused on reducing its impact during its operational stage, are being generating various questions in relation to the need and added value of the application of the Life Cycle methodology: what extent can the boundary system be simplified without reducing the accuracy of the results? What is the relationship between the impact reduced during the operational stage and the impact generated during the other stages of the life cycle? What are the most relevant parameters and/or stages when conducting a study and making a decision? In order to seek an answer to these questions on the basis of the EN 15978 and prEN 16627 standards, this research work proposed a quantitative methodology to allow assessment of the impact generated at each stage in the life cycle of an energy-efficient retrofitting of a building. The methodology proposed is validated using a building constructed in San Sebastian (Spain) in 1963. However, given the possible disadvantages of treating these results based on a single case of study as overall conclusions, the research proposes an exhaustive sensitivity analysis presenting new scenarios related to most of the parameters that have a direct influence on the method of calculation. After analysing all the new scenarios defined using these data, the results obtained make it possible to give an answer concerning the relationship between the increased accuracy of the results and the quantification of all the stages in the life cycle.Basque Government, Department of Education, Universities and Research's Personnel Research Training Progra

Two-Stage Multi-Objective Meta-Heuristics for Environmental and Cost-Optimal Energy Refurbishment at District Level

Energy efficiency and environmental performance optimization at the district level are following an upward trend mostly triggered by minimizing the Global Warming Potential (GWP) to 20% by 2020 and 40% by 2030 settled by the European Union (EU) compared with 1990 levels. This paper advances over the state of the art by proposing two novel multi-objective algorithms, named Non-dominated Sorting Genetic Algorithm (NSGA-II) and Multi-Objective Harmony Search (MOHS), aimed at achieving cost-effective energy refurbishment scenarios and allowing at district level the decision-making procedure. This challenge is not trivial since the optimisation process must provide feasible solutions for a simultaneous environmental and economic assessment at district scale taking into consideration highly demanding real-based constraints regarding district and buildings’ specific requirements. Consequently, in this paper, a two-stage optimization methodology is proposed in order to reduce the energy demand and fossil fuel consumption with an affordable investment cost at building level and minimize the total payback time while minimizing the GWP at district level. Aimed at demonstrating the effectiveness of the proposed two-stage multi-objective approaches, this work presents simulation results at two real district case studies in Donostia-San Sebastian (Spain) for which up to a 30% of reduction of GWP at district level is obtained for a Payback Time (PT) of 2–3 years.Part of this work has been developed from results obtained during the H2020 “Optimised Energy Efficient Design Platform for Refurbishment at District Level” (OptEEmAL) project, Grant No. 680676

Evaluating the Effect of Different Base Temperatures to Calculate Degree-Days

Degree-days are used as a forecasting tool to predict energy demand and for normalizing energy consumption to be able to compare between different properties across different years. The base temperature is the main aspect to accurately calculate degree-days. The aim of this study was to evaluate the effect of different base temperatures and their impact on the correlation between energy consumption and degree-days. The base temperature was selected as the standard 15 °C for the region, the balance temperature calculated with dynamic building simulations and the thermostat temperature setting as collected by questionnaires. The methodology followed is based on the analysis of 20 properties located in the cities of Bilbao, San Sebastian and Vitoria in northern Spain. The properties are a combination of flats and houses, from different construction periods, tenancies, occupancy and sizes. This study had highlighted the effect and impact of selecting different base temperatures for the calculation of degree-days and the correlation between energy consumption and degree-days. While the use of the balance temperature as base temperature could generate very good correlation, they were not so dissimilar from using the standard 15 °C base temperature to justify the amount of extra work required to generate the balance temperature. The use of the thermostat setting as an indication of the base temperature was not as reliable as the other base temperature methods in generating a good correlation to explain the energy consumption on the 20 properties investigated in this study

Positive Energy District (PED) Selected Projects Assessment, Study towards the Development of Further PEDs

Positive Energy District (PED) is a relatively new concept from which many projects are planned, however, only a few cases are currently close to be materialized, therefore, in this study the PED projects in operation and in implementation process in existing districts are gathered in order to serve as a base for future PEDs. In this sense, certain points of each selected project are highlighted due to their relevance within the project development and their replicability potential. Furthermore, intending to learn from the experience of the assessed case-studies, this paper aims to understand the current situation regarding PED implementation to simplify the development of further PEDs.The authors thank the Department of Architecture and the Vicerrectorate for Research of the University of the Basque County UPV/EHU for the financial support given for this researc

Environmental and Economic Prioritization of Building Energy Refurbishment Strategies with Life-Cycle Approach

An increasing number of studies apply life-cycle assessment methodology to assess the impact of a new building or to prioritize between different building refurbishment strategies. Among the different hypotheses to consider during the application of this methodology, the selection of the impact indicator is critical, as this choice will completely change the interpretation of the results. This article proposes applying four indicators that allow analysing the results of a refurbishment project of a residential building with the life-cycle approach: non-renewable primary energy use reduction (NRPER), net energy ratio (NER), internal rate of return (IRR), and life-cycle payback (LC-PB). The combination of environmental and economic indicators when evaluating the results has allowed to prioritize among the different strategies defined for this case study. Furthermore, an extensive sensitivity assessment reflects the high uncertainty of some of the parameters and their high influence on the final results. To this end, new hypotheses related to the following parameters have been considered: reference service life of the building, estimated service life of material, operational energy use, conversion factor, energy price, and inflation rate. The results show that the NRPE use reduction value could vary up to −44%. The variation of the other indicators is also very relevant, reaching variation rates such as 100% in the NER, 450% in the IRR, and 300% in the LC-PB. Finally, the results allow to define the type of input or hypothesis that influences each indicator the most, which is relevant when calibrating the prioritization process for the refurbishment strategy

Setting baselines of the embodied, operational and whole life carbon emissions of the average Spanish residential building

The construction sector, responsible for 37 % of global greenhouse gas emissions and 36 % of global energy consumption, is transitioning towards a low-carbon and low-energy model. Measuring and optimising Operational Energy and related emissions in the use phase of buildings has entered both markets and regulations. However, the Embodied Energy within construction materials and respective maintenance and end-of-life processes is still in the research phase. Moreover, Global Warming Potential baselines per built square metre need to be defined in the construction sector, integrating operational and embodied impacts. This research has the main goal of identifying for the first time the Whole Life Carbon (WLC) emissions of the average Spanish residential buildings of the period 1981–2010, broken down into Embodied Carbon (EC) and Operational Carbon (OC). For this purpose, first, a regular average and homogenised average of existing European baselines was performed; next, the average Spanish residential building has been defined and modelled with a real sample from year 2013, and its emissions calculated as Scenario 0; and finally, five new scenarios have been compared in order to understand variations in WLC and their EC and OC contributions. This research shows for the average multifamily building apartment in Spain, with a mean net floor area of 73.1 m2, a WLC baseline of 1944 kg CO2-eq·m−2, 30.8 % (559 kg CO2-eq·m−2) being EC, and the remaining 69.2 % OC. In Scenarios 1 to 3, the following are identified: a WLC reduction of 26.0 % (9.2 % EC) by using wood window frames, 0.8 % (2.7 % EC) by laying a wood inner floor, and 16.1 % (1.0 % EC) by insulating walls with recycled cork. All three items are calculated together in Scenario 4, giving a 36.9 % WLC reduction (9.5 % EC). Finally, Scenario 5 was modelled upon Scenario 4 materials, complying with the upcoming European Energy Performance of Buildings Directive as if built in 2021, reaching a potential WLC reduction of 63.4 % (2.8 % EC) from the original Scenario 0. These figures support technical and policy trends towards minimising the impacts of buildings. Focusing on decarbonisation, targets of over 60 % appear feasible with existing market solutions. Reductions of >80 % are also derived from other impact categories, such as Ionizing Radiation, Marine Eutrophication, and Water Consumption, while Freshwater Ecotoxicity increases by 15 %. The 18 ReCiPe Midpoint indicators plus Energy Footprint, are reduced by an average of 50.4 %.The authors are grateful for the support provided by the Life-Cycle Thinking Group (LCTG) with the grant funded by the University of the Basque Country (GIU21/010). The authors are grateful for the funding provided by the Department of Architecture of the University of the Basque Country (UPV/EHU)

Life Cycle Analysis Challenges through Building Rating Schemes within the European Framework

The decarbonisation of buildings is a crucial milestone if European cities mean to reach their mitigation targets. The construction sector was responsible for 38% of the GHG emissions in 2020. From these emissions, 11% is calculated to be currently embodied in building materials. In this context, an evaluation from a life cycle perspective is becoming increasingly necessary to achieve the objectives set. Currently, there are different building rating systems (BRS) at European level that allow the evaluation of the degree of sustainability of buildings. During this study, the authors have evaluated to what extent and how the most extended five BRS (NF Habitat HQE, VERDE, DGNB, BREEAM, and HPI systems) in the European framework have integrated the life cycle methodology during their evaluation process. Four methodologies have been used in the research in order to analyse these five systems: quantitative assessment, multi-level perspective, mapping–gap analysis, and expert interviews. Although each methodology has produced different results, the need to harmonise the evaluation criteria at the European level, the insufficient consistency of data software, and the availability of skilled LCA professionals for wider LCA market penetration, among others, should be highlighted. The quality and harmonised data of construction products is required for LCA to give aggregated and transformative results.This research was funded by the research project LOCAL-REGEN (PID2019-104871RB-C22), supported by the Spanish Ministry of Science and Innovation (Ministerio de Ciencia e Innovación) – State Research Agency/10.13039/501100011033

Environmental and economic optimization and prioritization tool-kit for residential building renovation strategies with life cycle approach

The most recent regulations, as well as the scientific studies, remark the importance of the evaluation of the entire life cycle on building renovations, relative to the environmental impact and economic feasibility, making the Life Cycle Assessment (LCA) the prioritizing analysis. The objective of the study is to develop a simplified methodology for the environmental and economic assessment of residential building renovations with life cycle approach. For this, a script-based tool-kit is developed: the first tool optimizes the thickness of envelope insulation based strategies; the second tool is for the prioritization of strategies by assessing their environmental performance and economic feasibility. In order to follow the objective, the development of the two tools is presented: both tools follow a parallel scheme where the input parameters are required by an excel file and the calculation script provides the results automatically by exporting the results excel file. The evaluation provides the quantification of the relative environmental improvement with the net energy ratio (NER), and the economic feasibility by the financial indicator of internal rate of return (IRR). The tool-kit is applied in a case study of a multifamily residential building. The results show, on the one hand, that the usability of the tool-kit can be determinant in the decision-making of stakeholders; and in the other hand, the importance of carrying out a dynamic assessment, taking into account the variation of the results caused by the uncertain parameters that differ in time. Moreover, the tool-kit can assist the development of cost-effective decarbonisation strategies.Part of the work presented in this paper belongs to the research project PIBA-PUE 2020(PUE_2020_1_0013) funded by the Department of Education of the Basque Government. Moreover, this research work is part of the corresponding author's Doctoral Thesis that aims to investigate the holistic assessment of technical renovation solutions of residential buildings in the Basque Country funded by the Predoctoral Training Programme for Non-Doctor Research Personnel of the Department of Education of the Basque Government (PRE_2021_1_0247)

Implementing User Behaviour on Dynamic Building Simulations for Energy Consumption

User behaviour influences the energy consumption of domestic properties with different range of variations and this has an effect on the results of building simulations based on default or general values, as opposed to implementing user behaviour. The aim of this paper is to evaluate and quantify the effect of implementing user behaviour in building dynamic simulation to calculate heating and domestic how water energy consumption to reduce the performance gap. The results for space heating and domestic hot water from dynamic building simulations will be compare to actual energy bills for a general building simulation technique and an calibrated building simulation, incorporating user behaviour details. By using user behaviour details to create calibrated building simulations, a correlation to actual energy bills of over 90 % can be achieved for a dataset of 22 properties. This study has shown that by incorporating user behaviour into building simulations, a more accurate estimation of energy consumption can be achieved. More importantly, the methodology approach allows the user behaviour parameters to be collected by means of a questionnaire, providing an easy and low budget approach to incorporate user behaviour into dynamic building simulations to reduce the performance

A Multi-objective Harmony Search Algorithm for Optimal Energy and Environmental Refurbishment at District Level Scale

Nowadays municipalities are facing an increasing commitment regarding the energy and environmental performance of cities and districts. The multiple factors that characterize a district scenario, such as: refurbishment strategies’ selection, combination of passive, active and control measures, the surface to be refurbished and the generation systems to be substituted will highly influence the final impacts of the refurbishment solution. In order to answer this increasing demand and consider all above-mentioned district factors, municipalities need optimisation methods supporting the decision making process at district level scale when defining cost-effective refurbishment scenarios. Furthermore, the optimisation process should enable the evaluation of feasible solutions at district scale taking into account that each district and building has specific boundaries and barriers. Considering these needs, this paper presents a multi-objective approach allowing a simultaneous environmental and economic assessment of refurbishment scenarios at district scale. With the aim at demonstrating the effectiveness of the proposed approach, a real scenario of Gros district in the city of Donostia-San Sebastian (North of Spain) is presented. After analysing the baseline scenario in terms of energy performance, environmental and economic impacts, the multi-objective Harmony Search algorithm has been employed to assess the goal of reducing the environmental impacts in terms of Global Warming Potential (GWP) and minimizing the investment cost obtaining the best ranking of economic and environmental refurbishment scenarios for the Gros district.OptEEmAL project, Grant Agreement Number 68067