Inevitably, the 21st century has initiated a series of developments in the construction industry, leading to its digitalization and resulting in a series of innovative approaches and practices. At the same time, the construction industry, being one of the main global environment polluters, should fulfil well-established, as well as novel, sustainability requirements in order to evolve in harmony with the rising concerns on the availability of natural resources. This overview study aims to present the main developments, research, and scientific challenges in the field of sustainable construction, emphasizing the field of energy. The study aims to present a state-of-the-art scientific discussion on the sustainable built environment topic by analyzing cutting edge topics in the fields of building elements and whole building energy assessment, of indoor air quality and low carbon buildings, as well as on sustainable energy systems and smart buildings. The study also presents the state-of-the-art in existing tools which are adopted for the assessment of the sustainable built environment, including the use of digital tools and building information modelling for the energy assessment of the built environment, as well as the application of Life Cycle Assessment on building-related processes. Cross cutting issues related to the analysis of the building sector in the Industry 4.0 era, such as sustainability management topics and environmental geomatics are also discussed. The study concludes in those fields which will be of interest of the scientific community in the following years, towards achieving the goals of the sustainable development of the building sector.

Sports halls must meet strict requirements for energy and indoor air quality (IAQ); therefore, there is a great challenge in the design of the heating, ventilation, and air conditioning (HVAC) systems of such buildings. IAQ in sports halls may be affected by thermal stratification, pollutants from different sources, the maintenance of building, and the HVAC system of the building, as well as by the activities performed inside the building. The aim of this study is to investigate thermal stratification conditions in accordance with the performance of the HVAC systems in the basketball training hall of Žalgirio Arena, Kaunas in Lithuania. Field measurements including temperature, relative humidity, and CO₂ concentration were implemented between January and February in 2017. The temperature and relative humidity were measured at different heights (0.1, 1.7, 2.5, 3.9, 5.4, and 6.9 m) and at five different locations in the arena. Experimental results show that mixing the ventilation application together with air heating results in higher temperatures in the occupied zone than in the case of air heating without ventilation. Computational fluid dynamics (CFD) simulations revealed that using the same heating output as for warm air heating and underfloor heating, combined with mechanical mixing or displacement ventilation, ensures higher temperatures in the occupied zone, creating a potential for energy saving. An increase of air temperature was noticed from 3.9 m upwards. Since CO₂ concentration near the ceiling was permissible, the study concluded that it is possible to recycle the air from the mentioned zone and use it again by mixing with the air of lower layers, thus saving energy for air heating.

Significant potential for reducing thermal energy consumption in buildings of moderate and cold climate countries lies within wind energy utilisation. Unlike solar irradiation, character of wind speeds in Central and Northern Europe correspond to the actual thermal energy demand in buildings. However, mechanical wind energy undergoes transformation into electrical energy before being actually used as thermal energy in most wind energy applications. The study presented in this paper deals with hydraulic systems, designed for small-scale applications to eliminate the intermediate energy transformation as it converts mechanical wind energy into heat directly. The prototype unit containing a pump, flow control valve, oil tank and piping was developed and tested under laboratory conditions. Results of the experiments showed that the prototype system is highly efficient and adjustable to a broad wind velocity range by modifying the definite hydraulic system resistance. Development of such small-scale replicable units has the potential to promote “bottom-up” solutions for the transition to a zero carbon society.

Thermal bridges play a major role in the thermal losses of the building shell and should be avoided, especially under winter dominant conditions and for high cooling degree days regions in Europe and worldwide. Since 2016 the requirement for all new buildings to achieve energy-efficiency class “A” came into force in Lithuania. One of the requirements to meet this class are detailed calculations of the thermal transmittance values of the longitudinal thermal bridges. The same requirement is also requested for higher energy-efficiency buildings that are qualified as “A+” (obligatory since 2018) and “A++” (obligatory from 2021 onwards) class buildings. The purpose of this study is the numerical investigation of the impact of thermal bridges on energy efficient buildings under humid continental climate conditions. For the purpose of the study, the energy performance of the thermal bridges of a class A building, situated in Lithuania, were analyzed, using the tool Therm of LBNL a two-dimensional conduction heat-transfer analysis, based on the finite-element method. The calculations of the thermal transmittance values of the longitudinal thermal bridges were implemented in accordance with the requirements of EN ISO 10211:2008 standard. Alternative construction designs, with the aim to minimize the thermal losses of the building shell are also presented and discussed in this study. This study showed that detailed calculation of the losses through thermal bridges may have a significant importance to avoid dew points and mold in sensitive parts of the building shell, but they have a minor influence for the energy certification criteria. The findings of this study are anticipated to provide useful feedback for the future development of the construction regulations in the Baltic countries, as well as in countries with humid continental climate conditions.

Demographic decline and population ageing present unprecedented challenges to housing systems in post-socialist Europe. With one of the European Union (EU)’s fastest shrinking populations, an underdeveloped social housing sector, and an ageing housing stock dominated by Soviet-era multi-family blocks, Latvia exemplifies these difficulties. Adaptive property reuse—repurposing underutilised buildings into age-friendly social housing—offers a potential solution, but its feasibility depends on complex economic, regulatory, social, and environmental determinants. This study investigated these determinants using a mixed-methods approach. Data were drawn from 312 survey responses, 15 policymaker interviews, 10 developer interviews, and focus group of 25 senior residents across Latvia. Exploratory Factor Analysis (EFA) was used to extract six determinant clusters: site selection, feasibility analysis, design and planning, implementation strategies, monitoring and evaluation, and scaling strategies. The findings demonstrate: (1) economic feasibility and regulatory clarity dominate stakeholder concerns, with financing gaps receiving the lowest ratings (M = 2.91); (2) implementation strategies emerged as the highest-priority determinant, emphasising governance capacity and structured execution; (3) significant trust deficits exist between developers and municipal authorities, undermining collaboration; (4) seniors prioritise design inclusivity and social integration, while developers emphasise cost efficiency and regulatory certainty; and (5) environmental sustainability consistently ranked lower (M ≈ 3.34) across all stakeholder groups due to pressing affordability concerns. Although municipal officers were intentionally oversampled (58%) due to their central role in Latvia’s housing governance, robustness checks confirmed the six-factor structure remained stable across stakeholder groups. This study contributes theoretically by contextualising adaptive reuse within shrinking cities and ageing societies and practically by providing a determinant-based framework for housing policy.