Buildings concentrate 40% of total energy used in Europe, so the improvement of the sustainability of constructions through a more efficient and use of buildings should be a great priority. In this regard, the wording of the Directive 2002/91/EC, related to European Energy Performance of Buildings promoted energy efficiency and the use of renewable energy in buildings.
In this respect, the Directive introduces the concept of nearly zero-energy buildings (NZEB), which are focused on minimizing the energy during the use of buildings by intensively using insulation materials and more advanced equipment.
NZEB requirements will have to be present in all new buildings beginning in 2021, and also all countries of the EU have to energetically renew 3% of public administration buildings on an annual basis. These renovations will suppose as a key to meeting the EU’s objectives to reduce greenhouse gas emissions and energy demand by 20%.
Currently, conventional passive interventions in buildings are focused on increasing the insulation of the building envelope to increase its energy efficiency during the use of buildings. But it doesn’t consider the environmental implications of obtaining or manufacturing the selected building materials that incorporate embodied energy to the building. For that, it is necessary to analyze the whole life cycle energy to identify the adequacy of each renovation proposal regarding the post-renovation energy performance of the building.
This study proposes an integrated methodology that assesses the embodied energy of the renovation of buildings using LCA (Life Cycle Analysis) and thermal dynamic simulation for the calculation of energy loads during the use of buildings. The proposed methodology was applied to the renovation of a university building located in the General Military Academy of the Spanish Army in Zaragoza in north-eastern Spain; following two different renovation proposals: a conventional renovation proposal and an NZEB renovation proposal based on the Passivhaus construction standard.
Obtained results show that both proposals achieved great energy savings, decreasing the energy consumption during the building use by between 60% and 80%. On the one hand, the conventional renovation project supposes less embodied energy and fewer environmental impacts but also generates fewer energy savings. On the other hand, Passivhaus renovation alternative supposes an increase in the amount of insulation material with respect to the current insulation systems and an increase in the embodied energy of the building.
However, the alternative does avoid impacts associated with reduced building energy consumption, achieving an operational energy savings of approximately 80%. Moreover, the most significant conclusion is the convenience of using these two combined methodologies, because it provides a more complete view of building life cycle and the energy and environmental implications of a renovation.
Additionally, to adhere more closely to the aims of low-energy building standards, this study analyzed the introduction of materials with the lowest carbon and energy contents. For that, cork was compared with the most common insulation materials installed in buildings. The cork material is extracted from the outer bark of the cork oak tree. This cork extraction is a sustainable process because it does not damage the tree, and following extraction, new bark re-grows.
The current insulation products made of cork do not meet the requirements to compete with the most commonly used insulation material because they do not imply better environmental performance of buildings. However, cork insulation products present ample room for improvement, as demonstrated by simulations of the proposed strategies throughout their life cycles, and could become more efficient and productive.
Summarizing, the introduction of sustainability in buildings have to be carried out in a comprehensive manner. It is important to avoid the transfer of environmental impact between different stages of building construction since the generated specific impacts could be made invisible. Moreover, this global incorporation of sustainability has to extend not only to energy, but all resources used during the total life cycle of buildings.
These findings are described in the article entitled Integrated lifecycle assessment and thermodynamic simulation of public building’envelope renovation: Conventional vs. Passivhaus proposal, recently published in the journal Applied Energy. This work was conducted by Jorge Sierra-PĂ©rez, JesĂşs Boschmonart-Rives, and Xavier Gabarrell from the Universitat Autònoma de Barcelona, and Beatriz RodrĂguez-Soria from the Centro Universitario de la Defensa. You can contact Jorge Sierra-PĂ©rez via email jsierra@unizar.es and on twitter @jsierraperez.