Energy efficiency has been identified as a way of addressing the need to reduce climate impact from fossil fuels. Furthermore, the ongoing twin transition may provide better and more energy-efficient control of buildings with systems such as building management systems (BMS). However, there appear to be barriers to investments in functional digital tools, as there are for other energy-efficient technologies for buildings. This paper is based on a questionnaire study with technology providers, decision makers and users of building management systems. The questionnaire included questions regarding barriers, drivers, and motivations for investments in BMS. Improved energy efficiency was found to be an important motivation for investments in BMS for users and decision makers, but the technology providers elevated more easy work as important. The main driver for investments in BMS was related to reduced energy costs, while for the decision makers, financial barriers such as risks and hidden cost were ranked highest. An important knowledge barrier was found as knowledge is needed for decisions about investments, use of BMS and decisions regarding IT security, such as handling of data. A key conclusion is the need for a facilitator, as knowledge is needed for decisions about BMS investments and for its use. On a broader scale, the paper argues for the need to include facilitators as a core part of future policies within the twin transition.

With concrete’s key role in construction and infrastructure, the reduction of its carbon footprint is critical for addressing global carbon emissions. One strategy to reduce environmental impact from concrete production is to replace cement clinker or fine aggregates in concrete with industrial wastes. Mine tailings, being a high-volume under-utilized resource, possess properties making it suitable for use as a partial substitute for cement or fine aggregates. This review article provides an overview of the recent findings within the topic of tailings-based concrete (TBC). Many of the identified publications aimed to describe the mechanical performance of TBC, and to optimize the concrete mix with respect to the strength and durability. The recommended cement replacement ranged from 5 to 25% and the recommended fine aggregate replacement ranged from 20 to 60%. In general, the compressive strength was decreased with increasing use of tailings as a replacement of cement. For the use of tailings as replacement for fine aggregates, the correlation was more complex, normally the mechanical performance enhanced at low replacement levels, until it reached an optimum after which it decreased. CO2 savings for replacing fine aggregate with tailings were up to 12% and for the cement replacement up to 30%. When assessing the environmental performance, most of the publications did not account for the loss of its mechanical performance, which could lead to the risk of underestimating the environmental impact. This review not only provides a basis for understanding the mechanical, toxicological, and environmental performances of TBCs, but also links the perspectives together, unveiling the connections between them. Moreover, this review presents an organized overview of the topic of TBC and points out topics for future research.

Night ventilation is a technique in which the indoor air and the building’s thermal mass is cooled down during nighttime to provide a heat sink available during the next day to help mitigating overheating and reducing the daytime space cooling demand. This paper proposes a framework on evaluating the use of mechanical night ventilation today and in the future. It considers analysis of the ventilative cooling system, including mechanical night ventilation, by means of key performance indicators that involve thermal comfort, energy use and resiliency criteria as suggested by IEA Annex 80. It, additionally, introduces an economic parameter in form of diurnal and nocturnal price ratio of electricity as economic trade-off between nighttime fan- and daytime fan and chiller use in terms of electricity. A historic office building in north-central Sweden is presented as a detailed case as to illustrate the use of the framework. The investigation was done using a validated model of the building in IDA-ICE building simulation program at both current climate and future climate in 2050s. It was revealed that an upgraded ventilative cooling system with three times larger capacity is required to fulfill thermal comfort. Even though mechanical night ventilation could result in the annual cooling source electricity saving intensity up to 0.9 kWh/(m²∙a) at extreme current climate (2018), it could just insignificantly reduce the total electricity use for space cooling (up to 2 %) and only at some night ventilation rates at all mentioned climates. Mechanical night ventilation, however, could be applied in an economically beneficial way if the electricity network has different nocturnal and diurnal electricity prices. A unitless index of maximum nighttime over daytime electricity price ratio was proposed representing the maximum tolerable price for nighttime electricity, given a daytime electricity price, based on night- and daytime ventilation electricity demand. For economically justified application of mechanical night ventilation, lower nighttime over daytime electricity price ratios were required for higher night ventilation rates. For the typical future climate with night ventilation rates larger than 2.6 ACH, it will be necessary to have nighttime prices that are lower than daytime if mechanical night ventilation is to be economical. The approach used in the framework can be applied to future research and practice, regardless of the case-specific parameters such as building type, climate zone, location, etc.

Cross-laminated timber (CLT) is one of the most sustainable, robust, and green building materials nowadays and is normally used for walls, floors, or roofs. The number of studies on CLT has increased significantly since 2010, which shows the acceptance and needs of CLT. Connection systems, rolling shear performance, and sustainability are the popular and main research topics within CLT, including wooden connections, metallic connections, adhesive and rod connections, aspect ratio, bonding performance, life cycle assessment, carbon emission, and environmental impact. Based on these three branches, the current study conducts a literature review on CLT. This review article aims to provide a valuable view and better understanding of CLT, which are linked to (1) promoting the usage of CLT and (2) summarizing the weaknesses of the CLT’s research. This article presents a full background of the CLT research and gives potential research directions for CLT as a structural material. It revealed that the design and analytical methodologies for novel timber and steel connections are the main trends. As for the CLT’s rolling shear performance, standardized testing protocol, environmental impact, and bonding quality need further development. Furthermore, the data collection, selection, and influence of different policies are important for the CLT’s sustainability assessment.

This  parametric study aims to predict the  performance of confluent jets ventilation (CJV) with variable air  volume (VAV) from four  CJV  design parameters. A  combination of  computational fluid dynamics (CFD), and response surface method (RSM) has  been used to  predict the  energy efficiency, thermal comfort and  IAQ  for  the  four  expected vital  design variables, i.e.,  heat load (XH),  number of  nozzles (XN),  airflow rate  (XQ) and  supply temperature (XTS).  The  RSM was  used to  generate a  quad-ratic  equation for  the  response variables exhaust temperature (TE),  sup-ply  temperature (TP),  PMV, DR, eT and  ACE. The  RSM  shows that  the  TE, TP and PMV were independent of the number of nozzles. The proposed equations were used to  generate setpoints optimized for  thermal com-fort  (PMV) for  summer, spring and  winter cases with different CLO  fac-tors  and  different TS under a  scenario where the  heat load varied between 10-30W/m2.  TE was  used as  setpoint to  regulate the  airflow rate  to  keep the  PMV values close to  zero. The  results show that  by adapting the TS to the CLO factor both thermal comfort and the energy efficiency can  be  improved. Further energy reduction can  be  gained by downregulating the airflow rate to keep the TP at a fixed setpoint when the  heat load is  decreased. This  means that  a  CJV  can  effectively be combined with VAV  to  improve environmental performance with good thermal comfort (-0.5<PMV <0.5,  DR <20%), above average IAQ (ACE = 106%) and  with a  higher heat removal efficiency (eT = 110%) than conventional mixing ventilation

As a preliminary investigation of the wind-driven purging process for densely built environments through the canopy layer, the ventilation efficiency of standalone semi-enclosed models incorporating a horizontal opening in the roof façade was investigated in the wind tunnel. For comparison, two models with different geometries were constructed, and each model was tested individually. Both models were equipped with replaceable roof covers, enabling the adjustment to the opening size. The ventilation efficiency was evaluated by continuous releasing and sampling of the tracer gas, from which the normalized purging velocity (PFVn) was derived. Additionally, the flow condition over the opening was monitored using the Laser Doppler Anemometer. It was found that separation flows from the frontal edge(s) of the model could introduce secondary circulations across large openings, resulting in dramatic increases in PFVn. Both the rectangular prism model and cylinder model possessed higher PFVn compared to prior studies on single-sided ventilation, while close values were observed with cylinder model mounted under the wind tunnel floor. Besides, the vertical distribution of integral length scales of streamwise velocity indicated the stratification feature of separation flows under low-turbulent incoming flow conditions. Measurement results provide validation data for further simulation studies including more detailed structures.

As a sustainable construction material, timber is more promoted than steel, concrete, and aluminum nowadays. The building industry benefits from using timber based on several perspectives, including decarbonization, improved energy efficiency, and easier recycling and disposal processes. The cross-laminated timber (CLT) panel is one of the widely utilized engineered wood products in construction for floors, which is an ideal alternative option for replacing reinforced concrete. One single CLT panel has an outstanding flexural behavior. However, CLT cannot be extended independently without external connections, which are normally made of steel. This article proposes two innovative adhesive-free edge connections made of timber, the double surface (DS) and half-lapped (HL) connections. These connections were designed to connect two CLT panels along their weak direction. Parametric studies consisting of twenty models were conducted on the proposed edge connections to investigate the effects of different factors and the flexural behavior of CLT panels with these edge connections under a four-point bending test. Numerical simulations of all the models were done in the current study by using ABAQUS 2022. Furthermore, the employed material properties and other relevant inputs (VUSDFLD subroutines, time steps, meshes, etc.) of the numerical models were validated through existing experiments. The results demonstrated that the maximum and minimum load capacities among the studied models were 6.23 kN and 0.35 kN, respectively. The load–displacement responses, strain, stress, and defection distributions were collected and analyzed, as well as their failure modes. It was revealed that the CLT panels’ load capacity was distinctly improved due to the increment of the connectors’ number (55.05%) and horizontal length (80.81%), which also reinforced the stability. Based on the findings, it was indicated that adhesive-free timber connections could be used for CLT panels in buildings and replace traditional construction materials, having profound potential for improving buildings’ sustainability and energy efficiency.

This study adapted the mean age of air, a time scale widely utilized in evaluating indoor ventilation, to assess the impact of building layouts on urban ventilation capacity. To distinguish it from its applications in enclosed indoor environments, the adapted index was termed the effective mean age of air (T_E). Based on an experimentally validated method, computational fluid dynamic (CFD) simulations were performed for parametric studies on four generic parameters that describe urban morphologies, including building height, building density, and variations in the heights or frontal areas of adjacent buildings. At the breathing level (z = 1.7 m), the results indicated three distinct distribution patterns of insufficiently ventilated areas: within recirculation zones behind buildings, in the downstream sections of the main road, or within recirculation zones near lateral facades. The spatial heterogeneity of ventilation capacity was emphasized through the statistical distributions of T_E. In most cases, convective transport dominates the purging process for the whole canopy zone, while turbulent transport prevails for the pedestrian zone. Additionally, comparisons with a reference case simulating an open area highlighted the dual effects of buildings on urban ventilation, notably through the enhanced dilution promoted by the helical flows between buildings. This study also serves as a preliminary CFD practice utilizing T_E with the homogenous emission method, and demonstrates its capability for assessing urban ventilation potential in urban planning.

Timber, a renewable resource with a low carbon footprint, has a giant potential to replace reinforced concrete (RC) structures in housing, which can decrease the environmental impact and lead to a healthier construction work environment. However, connections, as part of timber frames, are majorly made of steel and adhesives, which emit harmful pollution and negatively impact the timber structures. This study focuses on enhancing sustainability in construction by proposing adhesive-free timber connections for glued-laminated timber (glulam) panels. The study aims to contribute toward sustainable construction practices by reducing the reliance on adhesives and exploring alternative connection methods for glulam panels. This article presents four-point out-of-plane bending tests on glulam panels with innovative adhesive-free timber connections. The studied specimens compromised fabricated glulam panels and densified wood connectors made of pine and beech, respectively. Six different adhesive-free wood connections were designed and applied independently. Each connection was connected to two glulam panels by their end-grain sides. Therefore, twelve glulam panels, connected using these six connections, were tested. The panels had identical dimensions and materials. The connections were applied at the mid-span of the two connected panels. The experimental results on the flexural behavior, ultimate load, strength, and displacement of the six specimens are presented. The obtained mean load-carrying capacity of the specimens in the current research was greatly higher than that of the other specimens with different timber connections, such as timber-timber connections using compressed wood connectors. Additionally, the failure modes of the specimens were analyzed, which mostly exhibited the shear failure and delamination behavior. Most of the tested specimens failed in a ductile manner with a high ductility, which is suitable for the earthquake regions. The findings demonstrated the potential of using adhesive-free timber connections in glulam panels and contributing to the development of zero-energy buildings and sustainable construction practices while maintaining the structural integrity.

The use of timber as a building material is becoming increasingly popular thanks to its superior environmental performance compared with concrete and steel. However, timber structures rely on solid connections to improve their weak expansibility. Steel connections can be prone to corrosion over time, leading to the decreased structural integrity. Additionally, steel connections require more material and energy to manufacture and install compared with timber connections. This article focuses on the flexural performance of cross-laminated timber (CLT) panels with adhesive-free edge connections under four-point bending tests. First, numerical models of experimentally tested CLT panels were constructed using the finite element (FE) software ABAQUS. Then, these FE models were validated with the comparisons of their results with those of the experimental tests. Afterward, four new adhesive-free edge connections using timber for the CLT panels were developed in this study, helping sustainable construction. Utilizing the designed edge connections of the current study, forty-one parametric studies were numerically conducted on the connected CLT panels to investigate their ultimate loads, strains, displacements, moment capacities, failure modes, and effective stiffness. The factors affecting the edge connections’ load-bearing capacity were also examined and discussed. The study provides helpful insights into the development of CLT as a sustainable construction material with improved adhesive-free edge connections.