Residential areas retrofitting towards nearly Zero Energy Districts (nzed). A case study: Valladolid-Cuatro de Marzo

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1 Residential areas retrofitting towards nearly Zero Energy Districts (nzed). A case study: Valladolid-Cuatro de Marzo García-Fuentes, M. Á. 1 ; Vasallo, A. 1 ; García-Pajares, R. 1 ; Pujols, W. C. 2 ; Meiss, A. 3 1 Fundación CARTIF, Valladolid, Spain 2 ACCIONA Infraestructuras, Madrid, Spain 3 Universidad de Valladolid, Valladolid, Spain Abstract: Although the concept of nearly Zero Energy Buildings is well established among the new Buildings sector, in retrofitting processes it is necessary to think about integrated solutions at district level, leading to the new concept of nearly Zero Energy Districts. By following this new approach, the spectrum of Energy Conservation Measures (ECMs) that can be applied is wider. As a result, more ambitious objectives can be potentially achieved at urban scale. This paper introduces a Methodology for Energy Efficient Residential District Retrofitting, easily replicable in EU. Its application to the Cuatro de Marzo district in Valladolid (Spain) is depicted, focusing on the analysis and diagnosis of the current status of the district and the selection of the optimal combination of ECMs to be applied. This selection is based on a set of sustainability key performance indicators defined and calculated through the whole process. District, retrofitting, energy efficiency, nzed, methodology, replicability, indicators, IPD 1. Introduction: the Nearly Zero Energy District (nzed) concept The energy consumption in buildings is a key factor of environmental impacts as the energy use in buildings accounts for approximately 40% of the energy consumption and 36% of CO 2 emissions [1]. Since the EU aims at reducing the energy consumption and GHG emissions, the building stock plays a major role and the European Commission, under the Energy Efficiency Plan (Directive COM/2011/370), has identified the energy efficiency in buildings as a priority action in achieving the strategic targets [2]. The necessity of developing new methodologies and better business models to address projects for accelerating the urban regeneration towards nzed has become an indubitable issue in the recent years. In this context, the European project R2CITIES aims at developing and validating an integrated and systemic methodology for energy retrofitting at urban scale, achieving a methodological and scientific instrument able to support the implementation of solutions at district level. The main objective is to optimize the integral solution, following a holistic approach, to reach high levels of energy performance improvements while being costeffective and therefore, more capable of been bankable. This paper presents the application of this methodology to an area of the Cuatro de Marzo district, located in Valladolid, with two building typologies presenting a high level of energy consumption and low comfort conditions. 2. Identification of barriers and opportunities: the energy discussion in residential areas of the 50-80s in Spain In the middle of the 20 th Century, an important migratory movement from villages to cities 1

2 occurred in Spain as a consequence of a retarded industrialization process, emerging a drastic need of new dwellings. During this period, private promotions were not capable of covering the existing demand due to the economic situation. Aiming at solving the great demand of new houses, many public dwelling promotions in the 50-80s were executed in a very short time following a unique project. These integrated projects followed the principles of the hygienic housing and recurrent constructive and aesthetic solutions, resulting in homogeneous areas with typologies that are always of open blocks and towers. All these issues, along with the application of the International Style language and the technological and materials precariousness, allow to explain the deficiencies that are present in these buildings [3]. Under this scenario, apart from the great potential of energy savings and improvement of comfort conditions, the next premises must be considered; the great amount of grey energy already stored in these buildings, their conditions of centrality, urban infrastructures, mix of uses and social cohesion [3]. Considering also the typological and constructive homogeneity of these districts, the necessity of developing systemic and integrated solutions is clear, being easily replicable along the whole district, reducing costs and execution times. Although technological barriers are reduced at district level due to the wide range of applicable ECMs, economic and legal barriers are usually increased. The most important barriers in Spain are inherited from the housing policies, which have been focused on new buildings without coordination with the urban planning regulations. In this scenario, some regulations still remain out-dated, hindering the comprehensive rehabilitation of the building stock. Therefore, there is a strong need for administrative coordination in order to update the regulatory framework. Finally, the critical size of the interventions and the establishment of economies of scale is a key factor for the feasibility and success of this kind of projects [4]. 3. District energy retrofitting towards nzed methodology and strategies Under these premises, R2CITIES presents a systemic and integrated methodological tool based on a set of District Sustainability Indicators (DSIs) that allow the evaluation of the district status at different phases, ranging from the diagnosis of the current situation, the combinations of technologies, as well as the quantification of energy savings to finally, the improvement in comfort conditions. This methodology considers the change of scale from buildings to districts aiming at implementing scalable measures able to reduce timing and costs while supporting the exploitation of the urban morphology for this objective. Although the passive measures are applied at building level, the district concept affords cost reduction in both project and execution phases through the greater scale. On the other hand, active measures can be implemented from a district perspective achieving higher energy efficiency in order to meet the nzed objectives [5]. The advantages of considering the district as a global energy unit are based on the improvement of efficiencies through the implementation of centralized heating or cooling systems, the exploitation of different slopes and tiles for solar technologies or the utilization of common and public spaces for the installation of Renewable Energy Sources (RES) technologies to cover the demand Definition of District Sustainability Indicators (DSIs) Following the proposed methodology, the definition of the DSIs is a key factor in order to 2

3 evaluate the success of the retrofitting processes. These parameters refer to the data types that are measured or estimated in relation to a defined measurement boundary for verifying the impact of the ECMs and cover in a quantifiable manner energy, comfort, and environmental technical indicators together with economic, social and urban conditions. DSIs are specifically defined for considering the district as a global energy unit where energy and emissions are balanced globally and have been defined following the recommendations of the CONCERTO Premium guidelines [6]. In the context of the proposed methodology there exists a logical evolution in the indicators that are calculated for the whole project. The status of each indicator is identified at each specific stage, starting from the diagnosis at district level to the final energy savings, economic and social assessment stage, to support the process of design, execution, evaluation and decision-making of the most cost-effective and suitable combination of technologies R2CITIES: A 4-step methodology towards District Retrofitting The phases covered by the methodology are similar to any retrofitting process (Figure 1): (i) district audit, (ii) concept and detailed design, (iii) implementation of the construction works, and (iv) measurement and verification of energy savings, together with the assessment of the other DSIs, and acceptance plan. Figure 1:R2CITIES methodology for District Retrofitting The main innovative aspect of the methodology derives from the utilization of the Integrated Project Delivery (IPD) concept through Building Information Modelling (BIM) principles in order to improve the efficiency during all the phases of the retrofitting process and optimize the project results. Following this holistic approach based on IPD principles, all stakeholders cooperate in a collaborative manner through all phases, especially at the commissioning of Energy Conservation Measures stage. This enhanced process results in an intensive quality control plan, covering the whole process, aimed at improving the quality of the designed solutions, enhancing the design conformance to the clients needs and demands and ensuring high and functional quality of the final intervention. BIM tools are used to support this multifaceted collaboration, but also to store all the information of the district and the retrofitting process during the methodology life cycle. Step I - District Audit. The first phase, diagnosis, is supported by the utilization of Energy performance simulation tools and methods aimed at quantifying each DSI as per current 3

4 conditions of the district. A preliminary set of goals is defined, at this first stage, considering the client needs and demands. Data collection from different sources allows its quantification through energy performance simulations, monitoring and testing of certain parameters, nondestructive testing, analysis of energy contracts, or the distribution of questionnaires to owners to determine comfort, social or economic aspects. All these data are processed and DSIs are quantified through standardized calculation methods. Once the diagnosis phase has been completed, objectives and goals are reviewed to be aligned with the client needs. The ambition of these goals is determined by the barriers, especially those non-technical related to legal aspects and economic feasibility. To align client demands to technical or normative aspects, the involvement of all stakeholders during the establishment of goals is essential. Step II Evaluation of ECMs and optimum integral design. This phase starts with the concept design and finalises with the detailed design. In between, it is placed the negotiation process, which is the core of this second step. At this stage, sets of combined technologies are evaluated by simulation tools and calculation methods in terms of the defined DSIs. To decide the implementation of the most suitable set of technologies it is strictly necessary the definition of attractive financial models, which must be agreed with building owners. By considering all buildings of the district and the combination of technologies as a whole, the Return of Investment (ROI) can be reduced making the intervention more feasible under a specific investment plan. Thus, while for passive measures the existing returns of investment are assumable with difficulty when combining passive and active strategies ROI values are substantially improved. Step III Implementation of the construction works, operation and maintenance. The methodology is completed with the implementation of the construction works and the district commissioning, along with the verification of the achievement of those goals defined in the previous phases. Under traditional methods, in this phase new agents appear for the construction works or building management. In that sense, the IPD based methodology ensures that all stakeholders are present in the decision making process. In this process new barriers appear, especially related to the level of implementation of certain technologies or normative at district level. For that reason, this methodology intends to contribute to leverage normative under development as the European Directive of Public Procurement decrees regarding the future use of BIM for all works under a public contract. Step IV Measurement and verification of energy savings and acceptance plan. Due to the high cost to implement the ECMs and the expectation that they will reduce energy use, energy renovation programs at district level require careful evaluation. Energy, water or demand savings cannot be directly measured, since savings represent the absence of the use of these sources. Savings can be addressed by adopting suitable M&V protocols (e.g. International Performance Measurement and Verification Protocol -IPMVP- [7]) to compare measured use before and after the implementation of ECMs, making suitable adjustments for changes in existing conditions. 4. Concept application in a case study: Valladolid-Cuatro de Marzo district Projected in 1955 at the periphery, Cuatro de Marzo district is currently located at the end 4

5 of the main boulevard of Valladolid. The district is part of 6,473 dwellings promoted in Valladolid between 1940 and 1967 by the National Housing Institute (INV) and the Housing Union (OSH). Characterized by a high population density (200 inh./ha.) and high construction density (100 dw./ha), buildings are multifamily and multi-property. Also, a residential commonhold is established among all the flat-owners in each building to manage the common parts of the buildings. The retrofitting plan in the district is being promoted by the Municipality of Valladolid. Specifically, the municipal-owned company for ground and dwelling ("Sociedad Municipal de Vivienda y Suelo de Valladolid (VIVA, S.L)") will play the role of coordinator/supervisor of the refurbishment works and will articulate the negotiation with the owners to join to the retrofitting urban plan District audit and identification of barriers At this stage of project implementation, the first phase of the methodology has been applied in the district, covering the detailed diagnosis and audit report of this area under the methods and tools described within the methodology. Thus, energy and comfort conditions have been evaluated while defined the social, economic and urban aspects in order to establish the main targets and goals to be achieved through the intervention process accompanied by a detailed analysis of the main barriers identified. In order to evaluate the DSIs, energy performance simulations have been performed to characterize energy and comfort aspects, complemented by the data collected among the owners to evaluate the remaining indicators. For this purpose, a set of questionnaires have been distributed to the inhabitants, collecting aspects related to their profiles of use of the energy systems, the energy consumptions of the last year, their comfort perception, as well as social (e.g. age, social cohesion, etc.) and economic aspects (rent levels, unemployment rate, etc.) All these data have been collected and processed to quantify the DSIs under the R2CITIES principles as shown in Table 1. In terms of energy and comfort conditions, through the combination of energy performance simulation tools (Design Builder and Ecotect) and non-destructive testing (IR thermography and pressurization test) the main deficiencies have been characterized and a validated energy performance model has been defined to be used during the evaluation phases. The main problems detected in these buildings are due to the lack of insulation in the envelope, appearing also thermal bridges that in some cases provoke condensation problems. Also, although some dwellings have been renovated and do not present this problem, in most of dwellings there are high infiltration levels in windows that are similar to the levels existing in all building of this age. Specific barriers were detected when evaluating the social aspects. The majority of the residents are using the dwellings as a principal house, being around 19% of empty houses. The population is relatively aged, being the percentage of old people 28.8%, while the percentage of young people is only 9.9% and the average age is 53 years old. The fact that almost one third of the inhabitants are pensioners, together with the high level of 5

6 unemployment, approximately 20%, may result in a serious barrier in the negotiation phase. Therefore, these conditions make necessary the development of attractive business models, accompanied by an intensive awareness campaign in order to show the benefits of the renovation plan, not only in energy terms, but also in economic benefits in the long term. After the completion of the diagnosis phase, a first approach to the ECMs that can be implemented to achieve the goals (60% of total energy use reduction and 60% of global CO 2 emissions reduction) while overcoming the identified barriers has been carried out Evaluation of ECMs and optimum integral design In a first approach to the conceptual integral design, sets of ECMs were evaluated in terms of the DSIs defined in the methodology framework. These measures consider the improvement of the envelope insulation, by combining External Thermal Insulation Composites and ventilated façades including active measures for energy production (i.e. Building Integrated Photovoltaic). For the thermal production, a centralized heating system based on a biomass boiler is evaluated, while an improved control system for balancing the energy flows is also considered within the set of measures to be implemented. Table 1 summarizes the current and expected conditions in terms of energy, CO 2 and costs savings. ENERGY Table 1: Summary of District Sustainability Indicators under evaluation District Sustainability Indicators as-is-status foreseen status Density of final thermal energy demand kwh/m 2 yr kwh/m 2 yr Density of final energy consumption kwh/m 2 yr kwh/m 2 yr Peak load of electricity demand 8.37 kw 6.45 kw Peak load of thermal energy demand kw kw Degree of energetic self-supply 0 kwh/kwh 0.6 kwh/kwh Degree of accordance with national laws 27.28% - ENVIRONM. Greenhouse gas emissions kgco 2 /m 2 yr kgco 2 /m 2 yr SOCIAL ECONOMIC Average age of inhabitants 53 years old - Number of households that are unemployed 20% - Ownership structure Multi-property Multi-property Energy expenses for heating and DHW /yr/dw /yr/dw Energy expenses for lighting in dwellings /yr/dw /yr/dw Considering the package of technologies under analysis, active measures to be implemented (i.e. biomass centralized heating and DHW system and PV technologies) becoming an attractive model for the participation of an ESCO. Through this model, in which part of the total investment will be subsidized by the Municipality and the EU Grants, a company could be in charge of the remaining part of the investments, establishing an energy contract with the building owners. Also, when combining the passive and active measures, advanced business models appear, where the establishment of an association of a Construction Company and an ESCO, following a shared-risk model, can offer a more attractive product to the owners, establishing a long-term financial plan to facilitate the negotiation. 5. Discussion and conclusions 6

7 When addressing retrofitting processes in large urban areas, the implementation of the nzed concept leads to the development of new holistic and systemic methodologies. The R2CITIES methodology, based on the IPD principles and supported by the BIM concept, will improve the whole value chain, aiming at reducing the costs and timing of the whole process. These benefits, added to a wider scale, will make feasible and bankable the interventions. Those barriers to the widely application of the methodology have been identified. In particular, the main barriers found in the Cuatro de Marzo district are related to economic and social aspects. A significant part of the investment cost must be covered by the owners; therefore, the negotiation phase is essential. Moreover, the technological package bid from conceptual design should not be only attractive in terms of energy savings to ensure public subsidies but also economically feasible to assure the positive involvement of the owners. A set of passive and active ECMs has been defined to ensure the energy savings when retrofitting the district. This strategy also contributes to an improvement of the ROI by delivering new shared-risk models through the combination of financial entities, ESCOs, construction companies or other possible public or private investors being in charge of the initial investment needed, and establishing medium or long-term contracts with the owners. From this evaluation, it has been detected that there is a strong need for administrative coordination in order to update the regulatory framework, aiming at making easier the promotion of these integrated retrofitting plans at urban scale to achieve the nzed objectives. 6. Acknowledgements This research work has been funded by the European Commission through the 7 th Framework Programme, under the research project R2CITIES, Renovation of Residential urban spaces: towards nearly zero energy CITIES, Grant Agreement nº References [1] Lewis, J.O., Hógáin, S.N., Borghi, A. (2013). Building energy efficiency in European cities, Cities of Tomorrow - Action Today. URBACT II Capitalisation [2] COM(2011) 370. Final proposal for a Directive of the European Parliament and of the Council on energy efficiency and repealing Directives. European Comission, Brussels. [3] Meiss, A., Del Caz, R. & Álvaro, A., (2013). Rehabilitación de barrios de vivienda social. El ARI de la Rondilla en Valladolid. Ciudad y Territorio. Estudios Territoriales CyTET XLV (175) Ministerio de Fomento, Madrid. [4] Gee, L., Dijol, J. (2013). Financing Nearly Zero Energy Housing Projects. Power House Nearly Zero Energy Challenge. NHF & CECODHAS Housing Europe, Brussels. [5] García-Fuentes, M.A., Pujols, C., García-Pajares, R., Vasallo, A., Martín, A. (2013). Metodología de Rehabilitación Energética hacia Distritos Residenciales de Energía Casi Nula. Aplicación al barrio del Cuatro de Marzo (Valladolid). II Congreso EECN, Madrid. [6] [7] International Performance Measurement and Verification Protocol, Volume I 7