High performance building façades for Zero Energy Buildings in Greece: State of the art and perspectives

Abstract

Pursuing high energy performance with the least environmental impact of a building, along with ensuring the well-being of the occupants, is the ultimate goal of an institutional framework that addresses energy efficiency and environmental sustainability. The building sector is responsible for 38% of the total final energy consumption in Europe and is therefore in the epicentre of the effort to achieve improvements. This is being expressed by the targets of EU policies for 2030 and 2050, which set truly ambitious goals. Part of this effort is the improvement of the building's envelope thermal performance, along with the respective one of the HVAC systems, but also integrating those two in the best possible way. The façade is the crucial factor, as it is the interface between the building and its environment, but also between the environment and the HVAC system; it is truly the building's skin, which is therefore much more than a simple state boundary, if we want to have truly advanced buildings. Main scope of the paper is to present the results of an in depth investigation regarding the best available technologies and the upcoming trends of intelligent building façades, to be used in Zero and Positive Energy Buildings. This cannot be done without discussing the legislative and regulatory framework that applies for the building envelope, as solutions have to comply with regulations and standards, both national and international. In this line of approach an investigation of the practices and technical approaches best suited for Greece is being made, specifying their performance, possible drawbacks and approaches that are to be applied and the implementation of which is expected to contribute to the improvement of the buildings' performance. Furthermore, the constructional approaches and the effectiveness of both naturally and mechanically ventilated façades are discussed, along with their adaptation to the Greek building practices. The integration of ventilated façades with the building's HVAC systems may offer advantages, especially in spring and fall when preheating the air may lead to reduced energy requirements. In the opposite direction, heat rejection may be a problem in summer, where alternative cooling techniques can provide a solution. Finally, integration of innovative design elements such as the use of different final coating materials on the façades, the use of phase-changing materials (PCMs) and the integration of photovoltaic systems are evaluated.