Challenges and Research Trends of Energy Efficient Buildings

Innovative materials and systems for flexible and lightweight energy-efficient solutions in construction can help achieve the objective of more efficient buildings. This literature review categorizes these solutions into three categories: materials/systems topology, design flexibility from 3D-printing technologies, and innovative solutions for building envelope designs. The review shows a significant increase in interest in this research topic in recent years, with an average annual growth rate of about 73%, with most research focused on the design and thermal aspects, as well as the material typology and 3D-printing technologies. According to the review, flexible and lightweight systems can be applied to all building sectors, and retrofitting existing buildings may become the primary approach. However, there is no specific European regulation for these systems, and a more holistic design approach is needed, involving both designers/constructors and users, to plan for actual social, economic, and environmental impacts. Full article

Rapid construction with an energy-efficient approach is a major challenge in the present construction industry. Cement, a carbon-intensive material, is mainly used in the construction industry and hence increases the sector’s carbon footprint on the environment. The current review focuses on the study of 3D concrete printing (3DCP), in which cement is partially replaced with industrial byproducts such as ground granulated blast furnace slag (GGBS), fly ash, and silica fume. Walling material is primarily targeted in 3DCP. There is a need to include energy efficiency to achieve a thermally comfortable environment. The life cycle assessment (LCA) of concrete is studied to discover the potential conflicts affecting the environment. The sand-to-binder ratio is pivotal in determining the performance of concrete. The content of the supplements is decided based on this factor. The rheological, physical, and mechanical properties of 3DCP are studied further and analysed. GGBS demonstrates better performance in the compressive and flexure strength of concrete. The usage of fly ash and silica fume has reduced the thermal conductivity of the material, whereas GGBS has increased it. An LCA study shows that 3DCP can be made sustainable with the use of these supplementary cementitious materials. Full article

The construction world has changed day by day and is becoming more digitalized by introducing new technologies. Three-dimensional concrete printing (3DCP) is one such technology that has automated building process along with several benefits such as reduced material waste, reduced human hazard, and time savings. Traditionally, this technique utilizes cement to construct numerous structures, resulting in a significant carbon footprint and negative environmental impact. There is a need to find alternate solutions to reduce cement consumption. Alkali activation technology has replaced cement completely. The scope of development of alkali-activated 3D printable concrete utilizing agro-industrial byproducts is presented in this study. A review of the fresh and hardened properties of alkali-activated 3D printable concrete was the primary objective. The change in properties of 3D concrete mixes with the variation of additives that influence the ultimate strength parameters is presented. This study explores the curing conditions and in-depth behavior of uses of 3DCP in the construction industry. The environmental benefits over conventional concreting technology are presented. As per previous studies, the optimum mix composition per cubic meter concrete is 600–700 kg/m³ of binder content, 450 kg/m³ of alkali activator solution, and 600–800 kg/m³ of fine aggregate content. This study contributes to the making of 3D printable alkali-activated concrete. Full article

Economic growth and rapid urbanization have resulted in the increase in demand for infrastructure development. To meet this ever increasing demand, conventional construction materials such as concrete are used, which requires an energy intensive process that in turn impacts the environment adversely. Ordinary Portland Cement, being the dominant binder in the industry, contributes around 8% of worldwide annual carbon emissions, and this is expected to reach around 20% by 2050. Population growth has resulted in the significant increase in agro-industrial waste generation during recent years. Inadequate waste management raises a number of environmental concerns. With the growing economy and rising living standards, global raw material consumption is expected to double by 2060. The reutilization of waste materials will aid in their management, while conserving the available resources. Alkali-activated materials (AAM) have recently been introduced as an eco-friendly alternative to conventional binders with fewer environmental impacts. AAM reduce the need for Ordinary Portland Cement (OPC) by substituting it with supplementary cementitious materials (SCM), and therefore, reducing the amount of subsequent carbon emissions. Alkali activation is a complex chemical process between the precursors (alumino-silicate materials) and their dissolution in the activators. Different materials react to alkali activators in different ways depending on their properties. The current study aims to provide a critical review of potential agro-industrial wastes on the fresh and hardened properties of alkali-activated concrete (AAC). To understand the design and development of AAC, influencing the parameters such as the molarity of NaOH, alkali activators, and the ratio of the activators have been discussed in detail. The curing regime and its effect on the behavior of alkali-activated concrete are mentioned. The different admixtures used to regulate the properties of AAC are highlighted. AAC exhibited optimized embodied energy, operational energy, life cycle cost, CO₂ emission, and raw material consumption rates than the conventional concrete did. However, these results varied based on the precursors used in them. This paper focuses on the design and development of AAC, and it should be viewed as an important contribution towards the adoption of AAC in practical applications. The study presents the potential of AAM as a net zero binder in the making of sustainable concrete with enhanced properties. Full article

The construction industry has experienced phenomenal growth because of technological advancements in the past couple of decades. Prefabrication constitutes a sizeable share of this industry and is being adopted all over the world. The method of casting construction elements in a controlled environment and assembling them on-site has revolutionised the industry. Research on various aspects of the technology is ongoing around the world, and an impressive number of articles have been published. However, the prefab technology, materials used, and terminology have varied across locations, which may have hindered the method’s wider acceptability. By evaluating technical articles published between 1991 and 2022, this report analyses the present body of knowledge regarding prefab technology, its evolution, sustainability, and stakeholder views. This technology effectively contributes around 40% in time saving, 27% in cost reduction, 30% in reduced carbon emissions, and 84% in on-site wastage reduction. It also increases quality, gives a dependable alternative for meeting mass construction targets, is energy efficient, and provides environmentally conscious options. This paper contributes to the body of knowledge by providing a snapshot of the prefab industry spanning three decades, detailing a wide range of factors affecting the industry. Full article