Herramienta para la predicción de costes económicos y ambientales en el ciclo de vida de edificios residenciales. Fase de construcción

HS 32 33 HS Herramienta para la estimación de costes económicos y ambientales en el ciclo de vida de edificios residenciales. Fase de construcción Patricia González Vallejo Revista Hábitat Sustentable Vol. 8, N°. 2. ISSN 0719 - 0700 / Págs. 32-51 https://doi.org/10.22320/07190700.2018.08.02.03 HERRAMIENTA PARA LA ESTIMACIÓN DE COSTES ECONÓMICOS Y AMBIENTALES EN EL CICLO DE VIDA DE EDIFICIOS RESIDENCIALES. FASE DE CONSTRUCCIÓN A TOOL FOR ESTIMATING ECONOMIC AND ENVIRONMENTAL COSTS IN THE LIFE CYCLE OF RESIDENTIAL BUILDINGS: THE CONSTRUCTION STAGE. Recibido 07/09/18 Aceptado 20/12/18 RESUMEN Este trabajo presenta una herramienta para predecir los impactos económicos y ambientales del ciclo de vida de edificios de tipo residencial en fase de diseño, partiendo de un proyecto arquitectónico, del presupuesto del proyecto, de las bases de costes de la construcción, en particular, las de Andalucía y del indicador huella ecológica. La herramienta propone alternativas en el uso de recursos (materiales, mano de obra y maquinaria) y sistemas constructivos, pudiendo formar parte en la toma de decisiones para mejorar el impacto del ciclo de vida del edificio. Se analiza un caso concreto de edificio residencial de diez plantas sobre rasante y se obtienen los recursos empleados y su impacto económico y ambiental a nivel global y de forma pormenorizada, según las fases del proyecto. Los materiales son el recurso de mayor importancia y, específicamente, el hormigón o el cerámico son los que producen mayor impacto. Se realiza un análisis de sensibilidad, en el que se proponen diferentes alternativas de materiales para una solución constructiva y se obtienen los datos para decidir la opción más viable económica y ambientalmente. La herramienta es de fácil manejo para el usuario y puede ser base para la certificación de edificios y el desarrollo de valores estándares a emplear en políticas gubernamentales. Palabras clave herramienta, ciclo de vida del edificio, impacto económico, impacto ambiental, huella ecológica, bases de costes de la construcción, edificios residenciales. ABSTRACT This article presents a tool to predict the economic and environmental impacts of the life cycle of residential buildings in the design phase based on an architectural project; the project’s budget; construction costs databases, in particular those of Andalucía, Spain; and the ecological footprint indicator. The tool proposes alternatives in resource use (materials, manpower and machinery) and construction systems, as these can be used in decision making to improve the impact of the building’s life cycle. The case of a specific ten-floor residential building is analyzed, including the resources used and their general and specific economic and environmental impacts according to the stages of the project. The materials were found to be the resource of greatest importance, with the concrete or ceramic in particular producing the greatest impact. A sensitivity analysis was carried out in which different material alternatives were proposed for a building solution, and data was obtained to decide on the most economically and environmentally viable option. The tool is easy to use and can be the basis for building certification and the development of standard values for use in government policies. Keywords tool, building life cycle, economic impact, environmental impact, ecological footprint, construction cost databases, residential buildings. PATRICIA GONZÁLEZ VALLEJO Doctora Escuela Técnica Superior de Ingeniería de la Edificación (ETSIE), Universidad de Sevilla. Sevilla, España https://orcid.org/0000-0002-3106-0837 patriciagonzalez[email protected] Herramienta para la estimación de costes económicos y ambientales en el ciclo de vida de edificios residenciales. Fase de construcción Patricia González Vallejo Revista Hábitat Sustentable Vol. 8, N°. 2. ISSN 0719 - 0700 / Págs. 32-51 https://doi.org/10.22320/07190700.2018.08.02.03 HS 34 INTRODUCTION The knowledge resulting from the large number of studies on the environmental impact is finally reflected in the generation of calculation tools, normally addressed to the environmental certification of buildings. The development of this type of tools has been reinforced in recent years due to the need to create environmental policies for buildings that allow measuring that sustainability. Currently, there are a number of tools in Spain created from research projects that calculate the carbon footprint of buildings. LEED y BREEAM are the most widely used international instruments and in Spain they are managed by the Spain Green Building Council («SpainGBC VERDE tool website Available online» 2018) and BREEAM Spain («BREEAM.ES website Available online» 2018), respectively. They evaluate several aspects in order to obtain a final score, such as the CO2 emissions generated by the manufacture of the construction materials used and the energy consumed in the operational phase of the building. At a national level, SpainGBC VERDE presents the tool that assigns the highest percentage of points (~ 25%) to greenhouse gas emissions. On the other hand, there are the energy certification tools, such as CE3, CE3X, CERMA («Ministry of energy tourism and digital agenda, energy efficiency certification of buildings (Ministry of energy, tourism and digital agenda, Energy efficiency certification of buildings)» 2018) and the unified LIDER-CALENER («Spain MPW Unified Tool LIDER-CALENER Available online» 2018), developed by Spanish associations and universities. There are also several more specialized platforms that allow the detailed calculation of CO2 emissions of the resources, depending on the ratio of amounts defined by a project, such as the BEDEC cost database (“ITeC BEDEC website Available online” 2013) , developed by the Institute of Tecnología de la Construcción de Cataluña and whose environmental data come from the Ecoinvent ACV database (Ecoinvent center 2016), known, in turn, as one of the most complete at European level [63] and for its integration with the Simapro ACV software («PRé Sustainability SimaPro 8 Available online» 2018). To determine the environmental impact, various methodologies can be applied to the construction sector; currently, the tendency is to use the simplest ones. Thus, the ecological footprints (HE, by its initials in Spanish) (Wackernagel and Rees, 1996) and the carbon one (HC, by its initials in Spanish) (Weidema et al., 2008) are the most used ones: the results they produce are understandable by the non-scientific society and are easy to apply for decision-making and environmental policies (Bare et al. 2000). The indicator HE is increasingly used to quantify the growth of cities and control their effects, and more and more researchers are developing models for it (Lu and Chen, 2017; Yang and Hu, 2018). In this sense studies by Destacan Bastianoni et al. (2007), Li and Cheng (2010), Solís Guzmán, Marrero and Ramírez de Arellano (2013) and Teng and Wu (2014) are outsatnding, they have selected the HE indicator to evaluate the peculiarities of the construction sector. Some authors evaluate the materials used in the construction of buildings through indicators that generally follow the methodology of ACV (S. Lasvaux, Schiopu, J. Chevalier 2012; «UNE-EN ISO 14020 Environmental labels and declarations - General principles» 2002; F. García-Erviti, J. Armengot-Paradinas 2015), as well as the CO2 or energy emissions of the building’s life span (CVE) (Chau, Leung and Ng, 2015) (the conclusions of the phases usually match). The construction phase is concentrated in a short period of time (1-2 years); however, the decisions made during this phase influence to a large extent the results for the rest of the CVE. The operation phase is usually responsible for 80% to 90% of the CO2 emissions generated during the CVE (Radhi and Sharples, 2013), and almost 60% of which is caused by the demand of energy for heating and air conditioning (You et al., 2011). This paper presents a tool to assess the economic and environmental impact in the CVE, focused on the phases of manufacturing materials and construction, based on the data of the project budget, the construction cost basis and HE indicator. The tool is intended to be robust, flexible and easy to use, so that the indicator HE can be included in the certification of buildings, since none of the certification instruments is considered. In order to obtain the economic impact in question, the construction cost bases are used, which use Construction Information Classification Systems (SCIC, by its initials in Spanish) (Marrero and Ramírez de Arellano Agudo, 2010). In Spain, there are several construction cost bases, generally developed according to the autonomous communities, such as PREOC in Madrid, ITEC in Catalonia, PRECIOCENTRO in Guadalajara or BCCA in Andalusia. The tool proposed here uses the Andalusian one (BCCA), which has a stable, flexible and consolidated structure. The strength of the SCIC and the BCCA lies in the fact that they are capable of dividing a complex unit into parts, such as the construction of a building, and then adding them and forming the total. Other authors carry out the ACV and the analysis of the cost of the life cycle (CCV), and, from both, they make a complete study of the building. Recently, various tools and websites are being developed with this approach of economic and environmental analysis (Khan et al. 2018; Sesana and Salvalai 2013; Vasquez Palacios and Quesada Molina 2017) highlighting the importance of its use in the design phase to project more efficient buildings according to the economic and environmental HS 35 Herramienta para la estimación de costes económicos y ambientales en el ciclo de vida de edificios residenciales. Fase de construcción Patricia González Vallejo Revista Hábitat Sustentable Vol. 8, N°. 2. ISSN 0719 - 0700 / Págs. 32-51 https://doi.org/10.22320/07190700.2018.08.02.03 impact, and demystifying the cost increase of a more ecological building. Islam, Jollands and Setunge (2015), for example, perform a review evaluating and comparing the ACV and CCV of residential buildings, and to afterwards apply that analysis to a case in Australia. For this purpose, they use the Ecoinvent database (Ecoinvent Centre, 2016), the Simapro program (PRé Sustainability SimaPro 8 Available online, 2018) and an Australian construction cost base, which is not available openly and free of charge (Rawlinson, 2009). When they finish, they emphasize the importance of both analyzes, as well as the clear definition of limits and hypotheses. The building typology, the technologies used and the climate are also determining factors. This document explains, in the first place, the functioning of the proposed tool, according to the inventory analysis and the impact evaluation. Next, it is applied to a specific case: a residential building of ten floors above ground. Finally, the results and conclusions obtained are exposed according to the different proposed analyzes, which serve for the decision making in the design phase of the building and to define strategies around the improvement of the economic and environmental impacts. METHODOLOGY To explain the development and operation of the cost evaluation tool, the buildings’ ACV methodology is followed (UNE-EN ISO 14040 Environmental management — Life cycle assessment — Principles and framework 2006; UNE-EN ISO 14044 Environmental management — Life cycle assessment — Requirements and guidelines, 2006): definition of objectives and scope of application, analysis of inventory, evaluation of impacts and interpretation of results. In the present investigation the initial methodology of HE for the evaluation of housing construction developed by Solís-Guzmán, Marrero and Ramírez de Arellano (2013) and by González-Vallejo, Marrero and Solís-Guzmán (2015) is updated. The main difference with respect to the initial methodology is that the impacts produced by the resources (materials, manpower, machinery, electricity and water) are calculated using the CO2 emissions directly instead of the incorporated energy data (MJ). In the case of construction and demolition waste (RCD, by its initials in Spanish), transportation to the recycling plant is included, for which material transport assumptions are included. The mobility of workers is eliminated by adapting to the LCA life cycle cost standards (UNE- EN ISO 14020 Environmental labels and declarations - General principles, 2002). For the impact produced by workers’ food, the methodology of GFN is employed (Lazarus et al., 2014). For municipal solid waste (RSU, by its initials in Spanish), the data per person per year in the country under study and the corresponding emissions are applied, instead of making assumptions about the type of RSU generated at the construction site. In order to obtain the energy consumption in the work, empirical data are used. Finally, the impact of water is assumed to be generated by the energy needed for its supply (previously it was counted as HE of forests and now it is HE of energy). In addition, the methodology has been refined and systematized, which allows the development of eco-efficient construction standards capable of achieving sustainability certification. DEFINITION OF OBJECTIVES AND SCOPE OF APPLICATION The main objective is to obtain a tool to predict the economic and environmental impacts of CVE in the design phase, proposing alternatives for improvement in resource management: greener materials, more efficient machinery, optimization of labor and planning of RCD generated. As secondary objectives, it is proposed that the developed tool be used to quantify resources, waste and emissions generated and to evaluate the project in detail from the design phase. The tool focuses on residential buildings, in the phases of extraction and manufacturing of materials and in the construction of the building. It is considered that the plot is ready to execute the work, so that the urbanization works are not counted. Provisional installations for water, sanitation and electricity connections will be taken into account. It includes the transport of the material from the factory to the construction site and from the construction and demolition waste (RCD) to the management plant. In the construction phase, the impact of workers is evaluated according to the consumption of food and the production of solid urban waste (RSU), the impact produced by the machinery used, powered by electricity or fuel, the consumption of electricity and water during the work and the surface occupied. The impacts according to the HE indicator are accounted for per year. Likewise, the impacts produced by the resources included in the budget for material execution of the work (PEM) or direct costs (CD), as well as those from general data or indirect costs (CI), which are those resources of the work evaluated not attributed to a specific task (crane, scaffolding, construction technicians, etc.); and the data of temporary facilities such as the connections of facilities, work stands and consumption of resources (energy, water and personnel) associated to them are included (Marrero and Ramírez de Arellano Agudo, 2010). Herramienta para la estimación de costes económicos y ambientales en el ciclo de vida de edificios residenciales. Fase de construcción Patricia González Vallejo Revista Hábitat Sustentable Vol. 8, N°. 2. ISSN 0719 - 0700 / Págs. 32-51 https://doi.org/10.22320/07190700.2018.08.02.03 HS 36 INVENTORY ANALYSIS • At this point, all energy flows and incoming and outgoing materials of the system are quantified throughout their useful life, which are extracted from or emitted to the environment, for which the budget of each project based on of the construction cost bases is used. • Construction cost base: Used to draft the PEM budget of the project, which includes a detailed study of resources used and the analysis of the inventory proposed in the ACV to determine the impacts of the building. The BCCA (Consejería de Fomento y Vivienda 2016), whose structure and systematic classification organizes prices and their decompositions into resources of materials, labor and machinery (Marrero and Ramírez de Arellano Agudo, 2010; Ramírez de Arellano Agudo, 2004), which is used as the basis of the model developed by the tool. Building project: The tool has a database of more than one hundred projects (Ramírez de Arellano Agudo, 1988), which are updated to current regulations (CTE (Ministerio de Vivienda de España, 2006; Gobierno de España, 2008) and RCD) and whose main characteristics are presented in Table 1. It is the first data selection proposed in the tool. Measurements of the project: To define the project and estimate its impact, it is necessary to quantify the resources used based on the measurements defining the budget. The tool proposes a Qi type measurement, obtained thanks to statistical methods (Ramírez de Arellano Agudo, 1988) depending on the types of projects (González-Vallejo, Marrero and Solís-Guzmán, 2015). They are organized according to the systematic classification of the BCCA, as defined in Table 2, in chapters, sub-chapters, sections, groups and simple unit prices, grouped according to similar characteristics. The chapters are the first level of the classification (02 Excavations, 03 Foundations, 04 Sanitation, etc.) which, in turn, are subdivided into sub-chapters (in the case of chapter 04: 04C, hanging networks, 04E, buried networks, etc.); then, in sections (in the case of 04E: 04EA, boxes, 04EC, collectors, 04B, downspouts, etc.); and, finally, in groups (in the case of 04EC: 04ECF. Fiber cement collectors; 04ECH. Concrete collectors; 04ECP. PVC collectors, etc.), which are the ones that include the simple unit prices (PUS, by Project selection Characteristics Options No. of floors above ground: 123 4 5 or more No. of floors below ground: 0 1 2 Foundation: Isolated footings Continuous trench Reinforced slab Pile Structure: Load-bearing walls of brick factory Reinforced concrete Cover: Horizontal Sloped Use on the ground floor: Housings Commercial buildings Table 1. Selection of project typology in the tool according to typology and main characteristics. Source: González-Vallejo et al. (2015). its initials in Spanish) (in the case of 04ECH: 04ECH90002. m. Concrete buried collector of diameter 200 mm with overhangs, in the earth). PUS are made by, in turn, by auxiliary prices (PA, by its initials in Spanish) and basic prices (PB, by its initials in Spanish), which are those corresponding to the labor, materials and machinery necessary to execute such PUS (Consejería de Fomento y Vivienda, 2016). For the update of the projects, new Qi for air conditioning are calculated (in chapter 08. Installations: 08CA u, HVAC and 08CR devices, m² Radiators), solar energy (08N: accumulators, load-bearing structures and solar collectors) and management of waste (chapter 17), included in Table 2. One of the novelties of the tool is the one of introducing a series of deployable to define constructive systems, materials or type of machinery to employ, in function of the options posed, as it is specified in Table 2. In order to obtain the specific measurement of the project to be evaluated, the real area of the case study is applied to each Qi and, thus, obtain the quantities of the total resources needed (Q), according to equation 1: Where: Q: total measurement of a project item Qi: unit measurement of each item (u/m²) (unit of measurement of the item/m² of constructed area) S: Project surface Each Qi is associated to a simple unit price (PUS), from which the total resources will be obtained, based on the decomposition in PB and PA, which are collected to calculate each of the partial footprints that make up the total HE. Each resource produces one or several impacts, which are added to calculate the total environmental impact of the project. On the other hand, to define the economic impact, the PB is applied to each resource, then the PB and PA summation is made and, in this case, the unit price of item -04ECH90002 is obtained in this case - and, when applying the project surface, the total of the PUS for that project. Finally, adding all the items (PUS) results in the total budget, as shown in Figure 1. HS 37 Herramienta para la estimación de costes económicos y ambientales en el ciclo de vida de edificios residenciales. Fase de construcción Patricia González Vallejo Revista Hábitat Sustentable Vol. 8, N°. 2. ISSN 0719 - 0700 / Págs. 32-51 https://doi.org/10.22320/07190700.2018.08.02.03 STRUCTURE OF THE PROJECT MEASUREMENT Code Unit Concept Deployable options CHAPTER 02 EXCAVATIONS 02E m³ Excavations Shovel Backhoe 02R m³ Fillings Manual means Mechanical means 02T m³ Earth transportation Manual means Mechanical means CHAPTER 03 FOUNDATIONS 03A kg Reinforcement - 03P m Piles - 03E m² Formworks Wood Metal 03HA m³ Concrete reinforced footings Manual pouring Crane pouring Pump pouring 03HM m³ Mass concrete - 03H m³ Bnad concrete - CHAPTER 04 SANITATION 04A u Boxes In situ (brick factory) Prefabricated 04C m Collectors PVC Concrete Fibre cement 04B m Downspouts PVC Zinc Steel Galvanized steel CHAPTER 05 STRUCTURES 05AE kg Steel metal structures - 05F m² Forged Cement hollow brick Ceramic hollow brick 05HA kg Reinforcement - 05HE m² Formworks Wood Metal 05HA m³ Reinforced concrete - CHAPTER 06 MASONRY 06FB m² Block factories - 06DC m² Partition distribution (chambers) - 06DT m² Partition distribution (partitions) - 06LE m² Exterior brick factories - 06LI m² Interior brick factories - Herramienta para la estimación de costes económicos y ambientales en el ciclo de vida de edificios residenciales. Fase de construcción Patricia González Vallejo Revista Hábitat Sustentable Vol. 8, N°. 2. ISSN 0719 - 0700 / Págs. 32-51 https://doi.org/10.22320/07190700.2018.08.02.03 HS 38 CHAPTER 07 COVERS 07H m² Horizontal covers Transitable Not passable 07I m² Sloping covers Ceramic tile Cement mortar tile CHAPTER 08 FACILITIES 08CA u Air conditioning equipment - 08CC m Conduits - 08CR m² Radiators - 08EC m Circuits - 08ED m Lines and bypass Under tube: PVC In brick factory 08EL u Points of light - 08ET u Plug - 08EP m Earthing conductor - 08FC m Hot water pipes Copper Galvanized steel 08FD u Drains - 08FF m Cold wáter pipes Copper Galvanized steel 08FG u Faucets - 08FS u Sanitary Appliances Porcelain Steel 08FT u Water heaters/Heaters Electric Gas 08NA u Accumulators - 08NE u Support structures - 08NO u Solar collectors - 08NP m Primary circuit - CHAPTER 09 INSULATIONS 09A m² Acoustic insulation Glass fiber Polystyrene Polyethylene High density synthetic 09T m² Thermal insulation Glass fiber Polyurethane Polystyrene Mineral wool HS 39 Herramienta para la estimación de costes económicos y ambientales en el ciclo de vida de edificios residenciales. Fase de construcción Patricia González Vallejo Revista Hábitat Sustentable Vol. 8, N°. 2. ISSN 0719 - 0700 / Págs. 32-51 https://doi.org/10.22320/07190700.2018.08.02.03 CHAPTER 10 LINING 10AA m² Tiled With adhesive With mortar 10AC m² Plated Artificial stone Limestone Granite Marble 10CE m² Plastered - 10CG m² Garrisoned Cast Plaster 10S m² Pavement Ceramic Stoneware Hydraulic tile Wood deck Marble Limestone Granite Terrazzo 10SS m² Floors - 10T m² Roofs Fixing with rods Metallic fastening 10R m Finishes Limestone Wood Ceramic tile Marble CHAPTER 11 CARPENTRY AND SECURITY AND PROTECTION ELEMENTS 11CA m² Steel carpentry - 11CL m² Light carpentry - 11M m² Wood carpentry - 11MA m² Wardrobe - 11MP m² Wooden doors - 11B m² Railings Steel Anodized aluminum 11P m² Blinds - 11R m² Grilles - CHAPTER 12 GLASS 12A m² Glazing - CHAPTER 13 PAINTS 13PE m² Exterior paints Smooth elastomer With limestone 13PI m² Interior paints Smooth plastic With plain plastic Herramienta para la estimación de costes económicos y ambientales en el ciclo de vida de edificios residenciales. Fase de construcción Patricia González Vallejo Revista Hábitat Sustentable Vol. 8, N°. 2. ISSN 0719 - 0700 / Págs. 32-51 https://doi.org/10.22320/07190700.2018.08.02.03 HS 40 CHAPTER 17 WASTE MANAGEMENT 17AH t Iron and Steel - 17HA m³ Aggregates and natural stones - 17HC m³ Ceramic - 17HH m³ Concrete, cement and lime - 17MM t Wood - 17MP t Plastic and synthetic - 17RR m³ Mixed waste - Table 2. Definition of the project: Systematic classification according to criteria of the BCCA and options of the tool to select type of resources or construction systems. Source: González-Vallejo (2017). Figure 1. Internal operation of the tool to obtain resources and to define the impacts. Source: González-Vallejo, Muñoz-Sanguinetti and Marrero (2019). HS 47 Herramienta para la estimación de costes económicos y ambientales en el ciclo de vida de edificios residenciales. Fase de construcción Patricia González Vallejo Revista Hábitat Sustentable Vol. 8, N°. 2. ISSN 0719 - 0700 / Págs. 32-51 https://doi.org/10.22320/07190700.2018.08.02.03 DETAILED ANALYSIS OF RESOURCES Table 7 exemplifies the quantification of resources in the tool’s database to determine the impacts, according to data extracted from the BCCA. Each resource produces one or several impacts, as reflected in Figure 1. After studying the importance of resources (materials, manpower and machinery) in each chapter (Figure 3), it is noticed that the use of materials predominates, with the exception of the excavation and RCD management phases where the use of machinery and, to a lesser extent, labor (in all cases). Unlike the rest of the activities, in insulation, 50% of the resources used correspond to machinery, 45% to materials and 5% to manpower. Next, the materials and machinery are analyzed in greater detail, as they are the resources that define the impacts of the project. Machinery: In excavations, loader and dump truck are used; in the insulation of facades, the electrical machinery (compressor to project) used to place the thermal insulation of projected polyurethane. In the management of RCD, front loader, backhoe loader, dump truck and tilting mechanical trolley for internal transport are used. The impact can be reduced by using more efficient machinery with better performance. In the insulation work it is possible to try other alternatives of materials that do not need machinery and check if, in this way, the impact decreases. Materials: To the extent that materials are responsible, in almost all chapters, for 90% of the impact, they are analyzed at the project level and, in particular, in each chapter, to determine where the impacts come from. The project consumes a total of 1862.61 kg/m² of materials, which produces emissions of 316,52 kgCO2/ m². The HE of materials is 0,011 hag/m², being 0,08 hag/ m² HE of energy and 0,03 hag/m² HE of forests (wood). Next, the families with the greatest impact are selected and the CO2 emissions, the HE and the cost are analyzed, including the percentages over the totals (Table 8). It should be noted that ceramic and concrete materials represent the most significant in weight, in addition to a high economic and environmental impact. Steel has great importance in weight and lower environmental impact in relation to the rest of the materials; however it is the one that generates the greatest economic impact. On the other hand, wood stands out for its large amount of HE, contrary to its CO2 emissions, which are negative. Regarding the economic impact, steel, copper, concrete and ceramics are the most expensive materials. The chapters of greater impact are: foundations, structures, masonry, facilities and linings (Figure 4). In structure and foundation materials with greater weight and impact (kg / m²) are used, due to the presence of concrete, followed by masonry, which uses mostly ceramic material. Aggregates are also used in large quantities, in some phases, such as masonry and linings, but as they are natural elements they have much less impact. In facilities and linings, the impacts are more distributed due to the great variety of items and Figure 4. Materials used (kg/m²) in the chapters with the greatest impact of the project. Source: González-Vallejo (2017). Herramienta para la estimación de costes económicos y ambientales en el ciclo de vida de edificios residenciales. Fase de construcción Patricia González Vallejo Revista Hábitat Sustentable Vol. 8, N°. 2. ISSN 0719 - 0700 / Págs. 32-51 https://doi.org/10.22320/07190700.2018.08.02.03 HS 48 materials that include these phases, however, they have a high cost, being effectively the two chapters of greater economic impact. PROPOSALS TO IMPROVE THE ECONOMIC AND ENVIRONMENTAL IMPACT OF THE PROJECT To check the sensitivity of the tool, it is proposed to change the thermal insulation material of the facades in the project of the case study. The proposals according to the data of the BCCA are: projected polyurethane, initially proposed insulation (PUS 09TPP90037), fiberglass (PUS 09TPP00110) and mineral wool (PUS 09TPP90221). In Figure 5, we observe how resources vary according to the type of insulation. The new options do not use machinery and the impact is mainly produced by the material and, to a lesser extent, by the manpower. The economic and environmental impact of the three proposals is analyzed and the comparison is made in Figure 5. Fiberglass insulation is the most viable option from the economic and environmental point of view and the initial projected polyurethane proposal is the worst, since it produces greater economic and environmental impact. CONCLUSIONS Starting from the budget of the case study and the methodology of the HE indicator, the economic and environmental impacts are estimated, and it is inferred that the tool is very relevant for its use in the design phase of buildings. The conclusions indicated below, related to the case study, would be applicable to any building that is evaluated from these criteria of economy and sustainability. Thus, it is possible to determine the project phases with the greatest economic and environmental impact for the case study that, in general terms, are: excavations, foundations, structures, masonry, facilities and linings; in which, however, their level of economic impact does not usually coincide with the environmental impact, which forces decisions to be made in this regard. Therefore, in the design stage, the impacts of these phases and the materials used must be quantified in detail, and other solutions with a lower environmental impact can be proposed and decide whether to change them even if they have a higher cost. The concrete and ceramic materials are those that have greater weight in the total of the project, both being those that produce greater impact, which should be taken into account in the design of the building and try to reduce their use or use more environmentally friendly alternatives such as concrete recycling or ceramics involving more efficient manufacturing energy sources (pellets, for example). Figure 5. Economic and environmental comparison of the insulation chapter on the total project. Source: González-Vallejo (2017). The steel has little presence in weight and, nevertheless, its impact is very high, so that the overall impact of the project would be equally improved if we chose recycled steel. The results of HE, according to the current methodology, are lower when compared with those obtained in buildings with similar characteristics of previous investigations. This is mainly due to the update in the calculation of energy in the manufacture of materials, consumption of energy and water, and the impact produced by manpower. Therefore, the sensitivity of the tool in terms of the different material alternatives is demonstrated and also that fiberglass is the most suitable insulation. This study would be completed analyzing the operation phase of the building with each of the three alternatives and thus have the vision of the complete ACV and be able to make the best decision. The tool proposed here includes the construction characteristics most used in Spain, in recent years for residential buildings; the methodology is replicable and, given its versatility, allows its expansion including traditional materials from other climates, new more sustainable proposals, in addition to other types of foundations, metal or wood structures, different types of facades and finishes, etc. The tool is very flexible in terms of the possibility of expansion and inclusion of new types, construction systems and materials, and easy to use for the user. The use of the BCCA provides a stable and robust system that guarantees its viability and favors such flexibility. It is considered that it is an essential instrument in the decision-making when preparing a project from the design phase, since it allows to study different alternatives of resources and construction systems, according to economic and environmental points of view. HS 49 Herramienta para la estimación de costes económicos y ambientales en el ciclo de vida de edificios residenciales. Fase de construcción Patricia González Vallejo Revista Hábitat Sustentable Vol. 8, N°. 2. ISSN 0719 - 0700 / Págs. 32-51 https://doi.org/10.22320/07190700.2018.08.02.03 Regarding the weaknesses, the difficulty of access to some of the specific information of the HE indicator is considered, such as consumption data, or specific emissions of materials, energy or water resources, for the construction sector of each country. In future research, building typologies and resource alternatives, structural systems and proposed construction details can be expanded, and other environmental analyzes, such as embodied energy or the water footprint, can be included. In addition, the data used can be applied to energy certification tools and thus determine the impact of the operation phase of the building, completing the ACV, to facilitate decision making in the design phase with a view to improving the impact levels of the CVE. Likewise, it can be connected with BIM tools, which would facilitate the obtaining of project data. ACKNOWLEDGEMENT We thank Ministerio de Innovación y Ciencia for awarding the R+D+i project: Evaluation of the ecological footprint of the residential sector building in Spain (EVALHED) (BIA2011-25812) and the research group Architectura, Diseño y Técnica, (ARDITEC-TEP 172) of the Universidad de Sevilla. BIBLIOGRAPHIC REFERENCES ALBA-RODRÍGUEZ, M.D., MARTÍNEZ-ROCAMORA, A., GONZÁLEZ-VALLEJO, P., FERREIRA-SÁNCHEZ, A. y MARRERO, M. 2017. Building rehabilitation versus demolition and new construction : Economic and environmental assessment, Environmental Impact Assessment Review [en línea], 2016, vol. 66, n°, pp. 115-126. 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