Reforma nZEB en Barcelona


Como conseguir un proyecto de reforma nZEB

El siguiente post (al momento solo en ingles) presenta una parte del trabajo de investigación sobre reformas nZEB (edificios con consumo “casi” cero) desarrollado conjuntamente con el departamento de Architectural Science de Ryerson University Toronto (Canada) y Pich-architects.

El trabajo está enfocado en el desarrollo de un caso practico de una reforma integral de una edificio en Barcelona (area metropolitana). a través del estudio se consigue obtener las lineas guías para lograr bajar la demanda energetica del 70% y obtener así un edificio que consuma casi cero.. nZEB.

Este proyecto y el paper puede servir de referencia o simplemente de sugerencia para una reforma con objetivo nZEB en Barcelona.

Aqui un resumen del trabajo de investigación:

This paper presents a real case retrofit project of a school in Catalonia, Spain. The aim of the study is to develop a reference case for future projects of the same typology in the metropolitan area of Barcelona. The result offered different scenarios evaluated in terms of energy efficiency and costs, considering the influence of each factor over the decision making process towards the nZEB target.

The EPBD defines the framework for the nZEB, aiming to contribute to the reduction of energy use in European buildings, through the exchange of knowledge and best practices in the field of energy efficiency among the EU Member States. Moreover, the EPBD demands that each member translate into national legislation and practical guidelines, the minimum energy performance requirements for new buildings andfor the major renovation of buildings and building elements. In fact, each member has to consider the cost-optimal requirements according to its building stock and weather conditions.

The nZEB scenario for the project described in this paper was defined in order to comply with the most restrictive standards identified by the Spanish National Code(CTE). These parameters are:


  • 35% of savings in energy demand compared to the reference National Code case;
  • An energy certification class of “A”;
  • 70% of energy savings in the production of hot water;
  • 70% of electricity produced with Renewable Energy Technologies;
  • Max thermal transmittance for opaque elements of 0,2 W/(m2K);
  • Max thermal transmittance for transparent elements of 1,6 W/(m2K);


In Table 1, the framework that identifies the nZEB scenario for Spain is defined and compared with the current energy code.


Table 1.Spanish National Code standard – Comparison with the nZEB standard proposal

Proposed value for the nZEB scenario Current National Regulation – Residential Buildings (kWh/m2 y) Current National Regulation – Tertiary Buildings (kWh/m2 y) nZEB proposal – Residential Buildings (kWh/m2 y) nZEB proposal – Tertiary Buildings (kWh/m2 y)
Limits of energy demand of  heating and cooling 20 + 1000/ Building Area 25%savings in energydemand <15 35%savings in energydemand
Limits of energy consumption 50 + 1500/ Building Area Class B Class A Class A
% renewable energy production for Domestic Hot Water ≥40% ≥40% ≥70% ≥70%


It is important to remark that the measures adopted in the retrofit project aimed at achieving the nZEB standards, and had not to result in a significant increase in costs compared to a standard refurbishment project. On the other hand, the actions that were considered, aimed to improve the poor comfort conditions in the building in terms of lighting, thermal, and acoustic comfort.

nzeb-consumo-energiaThe structure of the project started with an accurate energy audit and a collection of data of the construction elements, HVAC system and energy consumptions through bills. The core part of the project was the definition of the retrofit strategy and the evaluation of each action in terms of energy saving goal. A significant part of the research was dedicated to Phase Change Materials (PCM) applied on the inner surfaces of the classrooms. The climate context and the activity profile made then suitable the analysis of the intervention based on PCM materials.

The research on PCMs has become one of the major topics in the building material field,. PCMs have the capability to store and release energy in the form of latent heat thanks to a solid-liquid/liquid-solid phase change at their melting point temperature and they may hence be used as thermal storage systems in order to store excespcm-materiales-cambio-fasesive heat from inside the building.

 The analysis focused on the most significant aspect such as the frequency of activation (FA), the surface temperature and the implication on the operative temperature and the energy demand. Finally, the economic study was developed for each proposal and for the combination of them to have a clear idea of the execution process and the organization of the different phases.pcm-materiales-cambio-fase-edificios

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