The content of the monograph contributes to the attainment of sustainable development goals as part of United Nations Agenda 2030 by considering the structural details on the thermal envelope of energy-efficient buildings (UN (United Nations) 2015). The research performed is in line with the EU Green Deal (EU Commission 2019b) and also targets the development of the new European Bauhaus initiative (EU Commission 2021). A structurally safe, sustainable and energy-efficient details will improve the competitiveness of energy-efficient buildings as a change agent towards a circular and sustainable building sector. As the market for energy efficient buildings spread to earthquake-prone areas, the structural details on the building envelope must be adapted to ensure sufficient structural resistance. Furthermore, with the Renovation Wave in Europe aiming to renovate and refurbish 30–40 million homes in the next ten years, the contribution of this monograph is even more important.

The overall goal of this work is to assess energy-efficient building details for seismic regions with properties meeting the needs and demands of a sustainable-oriented market. The presented results impact several different aspects, which correspond to the attainment of sustainable development goals and also relate to the EU Green Deal:

  • Good Health and Well-Being (SDG3): Well-designed building structural details are aimed at increasing the good indoor environmental quality in energy-efficient buildings (e.g. by reducing moisture defects, using materials with less volatile organic compound emissions etc.), resulting in high living comfort which positively affects the health, well-being, and work performance of users.

  • Decent Work and Economic Growth (SDG8): Off-site manufacturing of building components, simplicity and automation in the construction of energy-efficient buildings shortens the building process. By implementing well-designed energy-efficient structural details aimed also at modular construction, the safety in the working environment will significantly increase. Well-designed structural details and new concepts can open new markets and hence reach stable economic growth.

  • Industry, Innovation, and Infrastructure (SDG9): Development of energy-efficient buildings with innovative structural details brought new products on the market (e.g. load-bearing materials with thermal insulation capability), and raised the potential for industry and market development in the construction sector, especially due to flexibility, adaptability, low-maintenance need and recyclability.

  • Sustainable Cities and Communities (SDG11): The next-generation of energy-efficient buildings provides potential for new quality living areas, which can consequently result in more sustainable ways of living. Technological innovation in various forms and digitalisation will contribute to the sustainable transformation of the built environment on all levels (building, district, city).

  • Responsible Consumption and Production (SDG12): for the built environment to become socio-economically effective and sustainable, circular resource flows and the circular economy are major driving forces. The work is aimed at the building sector by improving building efficiency (efficient use of natural resources), increasing simplicity of structural details and technology transformation.

  • Climate Action (SDG13): The manufacture, transportation, installation, maintenance, and disposal of building products/materials amount to around 11% of global emissions. The methodology in this work is aimed at reducing greenhouse gas emissions and emission intensity in energy use, which is critical considering the urgency of climate action and a priority of the ‘greener, carbon free Europe’.

In the monograph, the term ‘energy-efficient building’ applies to all buildings that take into account modern requirements for a better thermal envelope and a lower energy consumption. Directive 2010/31/EU on the energy performance of buildings (DEUS 2010/31/EU) was adopted at the EU level in 2011 to reduce energy consumption in households. The Directive stipulates the construction of nearly zero-energy buildings beyond 2021, which has so far been prescribed by EU member states in various incentives and acts with mixed success (EU Commission 2019a). The term ‘nearly zero-energy buildings’ is defined in the Directive and signifies a building with a very low energy consumption, which can cover all losses from renewable sources. The term ‘energy efficiency’ defines the efficiency of a building in terms of energy used for heating and cooling, ventilation, air conditioning, and efficient hot water supply.

The German passive house standard (PassivHaus; hereinafter referred to as ‘the PH standard’) can be stated as an example of the building energy efficiency standard. The provisions and requirements of the PH standard have been amended for the design of the first passive house to the present, and the details of passive houses will continue to be developed and improved (Passivhaus Institut 2012). The PH standard is among the first standards to numerically define requirements to achieve high energy efficiency, setting an example for many other building energy efficiency standards. According to Dequaire (2012), standards applied by various countries to regulate the construction of energy-efficient buildings includes Swiss Minergie-P (2009), French BBC-effinergie (2012), Norwegian prNS 3701 (2011), Danish Damnarks Lavenergibygning klasse 1 (2009), and British Code for Sustainable Homes level 6 (2009). The provisions of all these standards contribute to the understanding of modern energy-efficient building design. The objective of such a design is to build buildings of the highest quality possible by taking into account the local climate, making use of renewable sources and ambient energy (heat and cold), and using locally available materials with a low environmental impact for construction (see, for example, Krainer (2011), Küçüktopcu and Cemek (2018), AzariJafari et al. (2021), Hoxha et al. (2017)). To attain these objectives, the architectural design of buildings is crucial. From the aspect of energy efficiency, it must provide: (i) a carefully planned orientation and location of a building to optimise requirements for energy conservation; (ii) a favourable ratio between the building envelope and volume to avoid unnecessary division of buildings and elements that could cause thermal bridges; (iii) the sunlight exposure of the building envelope with the thermal energy function; (iv) the shape and ratio of glazing to gain as much heat in winter as possible and protect against excessive sunlight exposure and heating in summer; (v) well-designed and planned surfaces suitable for solar thermal collectors and other devices that utilise solar radiation; and (vi) a good thermal insulation of the thermal envelope and other transparent elements (e.g. windows) on the building envelope.

Due to all the above-mentioned regulations, the construction of various types of energy-efficient houses has become widespread in Europe in recent years. Common characteristics of such buildings are that the thermal envelope must be uninterrupted—also under the building or its foundations, and thermal bridges must be prevented. Numerous details are used in practice for this purpose, which were developed in Western Europe or Scandinavian countries with a low risk of considerable seismic loads. The structural systems of passive houses were also developed in low seismic hazard areas, making them suitable for vertical and wind loads. However, there is no guarantee that their behaviour will be appropriate and ductile in the event of cyclic seismic loads. It must be noted that inserting soft insulation layers with better vertical load-bearing capacity extends the fundamental period of a structure, as a structure on the thermal insulation layer vibrates more slowly than on the ground. Most such buildings are low-rise buildings and have very short fundamental periods. By extending the fundamental period, they can be moved to the resonance part of the design response spectrum (the periods within constant acceleration plateau). This means that in stiff buildings on poor soil 2 to 3.5-times higher forces acting on the building could be expected. The results of seismic analyses exposed that the height of such buildings must be limited to three or four storeys, depending on the slenderness, stiffness, and mass of the building.

Additionally, so-called base insulation blocks are frequently used in passive houses, which are inserted between the upper part of the structure and the foundation slab or unheated basement to prevent thermal bridges. In an earthquake, the shear strength of walls and columns is very important and may be reduced to the point where the structure's earthquake resistance is no longer sufficient by inserting such insulation load-bearing elements designed only for vertical loads. Studies have shown that such technology transfer can be dangerous, particularly in larger and heavier multi-storey buildings in high seismic hazard areas. Studies have also shown that, when designing earthquake-resistant details, sufficient attention must be paid to their resistance to horizontal actions. The energy efficiency of certain details is inversely proportional to their earthquake resistance. Therefore, we have developed a special detail evaluation methodology, which is presented in more detail in Chap. 5 of this monograph.

Due to the unique character of energy-efficient buildings, it is frequently difficult to meet all the requirements for earthquake-resistant construction, as the environmental and energy-efficiency criteria must also be taken into account to reduce environmental impact and increase thermal comfort for users of buildings. We have found that certain requirements of energy-efficient and earthquake-resistant construction are diametrically opposite. The use of mere technical guidelines provided by standards for earthquake-resistant construction, e.g. Eurocode 8 (CEN 2005), can result in the significant deterioration of details in terms of energy. Such requirements include the uniformity and continuity of the load-bearing structure or structural regularity by height without major changes in its load-bearing capacity and stiffness. These general principles of standards may result in the interruption or deterioration in the thermal envelope, causing thermal bridges in the thermal envelope, which must be prevented to comply with the current energy-efficient construction regulations. On the other hand, the problem can be viewed from the opposite side. Taking into account the recommendations in energy-efficient construction standards on continuous thermal insulation may lead to interruptions and discontinuity in the load-bearing structure, which may significantly change the response in earthquake-prone areas. An interesting example of a problem in this field is fixing balcony cantilevers without a thermal bridge, since thermal insulation is most necessary at the precise location of the highest bending moment reaction of the cantilever.

The structural safety of energy-efficient buildings has not yet been extensively studied, since most first energy-efficient buildings were smaller, making them less vulnerable to seismic actions. The technology of energy-efficient building construction has expanded to almost all types of buildings (including large buildings, such as blocks of flats, large office buildings, etc.). Therefore, higher loads on crucial structural details may be expected. In the monograph, we analyse as many details of energy-efficient buildings as possible, and find their specifics and limitations of their use in earthquake-prone areas. The most important general findings of our research in this field are: (i.) the principles of energy-efficient buildings and their structural details for preventing thermal bridges can reduce earthquake resistance of structures in comparison with conventional earthquake-resistant construction; (ii.) certain details of energy-efficient buildings used in non-earthquake-prone areas cannot be transferred to earthquake-prone areas; (iii.) suitable design can improve the response of energy-efficient buildings for them to comply with current regulations on the design of structures for earthquake resistance and the principles of energy efficiency; (iv.) with the new proposed methodology, we can establish the extent to which environmental and energy-efficiency, and technical and structural aspects are taken into account in structural details, and recognise critical (poorer) details in terms of earthquake resistance.

In the monograph, the possibilities to use the concepts and details of energy-efficient buildings in earthquake-prone areas are explored, and analytical and practical approaches to improve their safety are presented. The authors aim to facilitate progress in earthquake engineering, architecture, and other disciplines dealing with the design of quality earthquake-resistant and energy-efficient details of buildings.