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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 CO2
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 20-20-20 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 20th Century, an important migratory movement from villages to cities
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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.
3.1. Definition of District Sustainability Indicators (DSIs)
Following the proposed methodology, the definition of the DSIs is a key factor in order to
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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.
3.2. 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
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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
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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.
4.1. 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
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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 CO2
emissions reduction) while overcoming the identified barriers has been carried out.
4.2. 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, CO2 and costs savings.
Table 1: Summary of District Sustainability Indicators under evaluation
District Sustainability Indicators
ENERGY
as-is-status
foreseen status
Density of final thermal energy demand
111.52 kWh/m2yr
66.91 kWh/m2yr
Density of final energy consumption
194.20 kWh/m2yr
95.02 kWh/m2yr
Peak load of electricity demand
8.37 kW
6.45 kW
Peak load of thermal energy demand
26.43 kW
15.85 kW
0 kWh/kWh
0.6 kWh/kWh
Degree of energetic self-supply
Degree of accordance with national laws
ENVIRONM.
SOCIAL
ECONOMIC
27.28%
-
Greenhouse gas emissions
43.45 kgCO2/m yr
10.90 kgCO2/m2yr
Average age of inhabitants
53 years old
-
20%
-
Ownership structure
Multi-property
Multi-property
Energy expenses for heating and DHW
822.14 €/yr/dw
298.01 €/yr/dw
Energy expenses for lighting in dwellings
314.78 €/yr/dw
252.29 €/yr/dw
Number of households that are unemployed
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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
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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 7th Framework
Programme, under the research project R2CITIES, Renovation of Residential urban spaces:
towards nearly zero energy CITIES, Grant Agreement nº314473.
7. 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) 2013. 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] http://concerto.eu/concerto/about-concerto/about-con-intro.html
[7] International Performance Measurement and Verification Protocol, Volume I
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