Low Energy Buildings Research Articles

Ways to decarbonize the construction industry as a modern challenge for obtaining low-carbon building materials

The analysis of modern approaches and ideas for the production of new building composite materials with a low carbon footprint, including those obtained using recycled materials from man-made waste, is presented. It is concluded that the reduction of carbon dioxide emissions in the production of low-carbon concretes occurs as a result of replacing part of the cement with other types of binders or special fillers that ensure the preservation or improvement of the basic parameters of the structure of the building material, or due to technologies that reduce the clinker fraction of the binder while maintaining the specified properties of concrete. The leaders in the world practice in the field of low-carbon materials science are noted. The relevance of the development of the topic of environmental safety and sustainable development is indicated.

Night cooling by hybrid ventilation – analytical predictions of the purge time

Many low-energy buildings rely on a night purge strategy during periods of excessively warm weather in order to flush out excess heat and thereby help prevent overheating on the following day. A typical purge utilises either a mechanical or a natural displacement ventilation strategy. However, we investigate purging by the simultaneous application of natural and mechanical ventilation, i.e. using a hybrid strategy. Hybrid ventilation is widely promoted as a means of overcoming the inherent limitations of both natural and mechanical ventilation, although relatively little is understood about its operation on a fundamental level. Such was the lack of knowledge on hybrid ventilation that even the time taken to complete a purge was not known at the outset of this work. Through the development of a mathematical model, supported by a series of laboratory experiments, we show that the time taken to purge a room using hybrid ventilation can be established analytically, and is controlled by two ratios: (i) the flow rate of the mechanical supply (the ‘forcing’) relative to the initial flow rate through the vents in the absence of mechanical forcing, and (ii) the ratio of the floor-level and ceiling-level vent areas. The analytical predictions show close agreement with our measurements. Supplementing a natural displacement ventilation strategy with even a modest mechanical supply can reduce significantly the time taken to purge warm air from a room. Some of the implications of our findings for preventing overheating in buildings by increasing the efficacy of a night cooling strategy are discussed. Practical Application This research is directly applicable to practitioners involved in the first-order design of hybrid ventilation systems – particularly designs which incorporate a ‘night purge’ regime. Governing equations are derived and the key parameters controlling the rate of purging of warm air are revealed, allowing informed first-order design decisions to be made without the need for expensive and time-consuming computational simulations.

Impact of newer climate data for technical analysis of residential building energy use in the United States

In this study, we describe an analysis indicating the relative importance of newer hourly weather files for simulation analysis of the energy use of residential buildings in North America.Results show that older TMY3 (ending 2005) data compared with newer TMY2021 (2007–2021) data are less appropriate for the best prediction of low-energy buildings. The balance of heating and cooling is significantly altered in the more recent TMY files with potential impacts on best performing energy efficiency measures. With 64 high profile North American locations evaluated, we found heating to be approximately 11% lower with the newer data, while cooling was increased by a similar amount percentage wise. However, the dominance of space heating in North America made decreases to heating considerably larger in an absolute sense so that overall space conditioning energy fell.Small changes in annual temperature can have large impacts. For all electric homes with air source heat pumps, we found that a change of 1 °C to outdoor temperature can produce about a 19 % change in space conditioning energy. The newer data also shows increased average solar electric output from simulated rooftop photovoltaic systems, likely due to more sophisticated solar irradiance data. Water heating was about 3 % lower given rising groundwater temperatures and inlet water temperatures to water heating systems. Results also showed that the newer data tended to increase savings from comprehensive building efficiency efforts in all electric buildings. This largely takes place because higher temperatures in winter allow air source heat pumps to meet heating needs more efficiently. Generally, the direction of these influences ease pathways to reach zero energy buildings in North America.

The role of photovoltaic technology in achieving net zero energy target in residential buildings

The construction sector plays a pivotal role in reducing carbon emissions, facilitating the transition to renewable energy and promoting sustainable development. In the European Union, where decarbonization strategies are currently proving most incisive, legislative measures such as the Energy Performance of Buildings Directive (EPBD) have catalyzed a marked increase in the prevalence of energy-efficient buildings. In terms of decarbonization, such efforts can be achieved by massively applying Renewable Energy Sources (RES) both in new buildings as well as in existing ones, which represent the majority of the EU building stock. For such reasons, Building-Integrated/Applied Photovoltaic (BIPV/BAPV) systems offer a promising avenue for providing clean energy to the building sector. Nonetheless, despite their potential, the practical implementation of these systems on buildings faces feasibility constraints, mainly due to the limitation of the available installation surface.In such a framework, this study conducts a comprehensive evaluation of BIPV/BAPV installations potential to fulfill the electricity needs of residential buildings (i.e. achieve the net zero energy target), with a particular focus on multi-family structures within the European contest. A reference high-performance building, already assessed by the authors and therefore very well documented, was used as a test bed through detailed dynamic energy simulations. According to obtained results, the net zero energy target can be achieved for energy-efficient buildings with up to 3 and 5 storeys, in Nordic and Mediterranean climatic conditions, respectively. Assuming instead reference maximum consumption thresholds (resulting in higher energy consumption), achievable results are more restrictive, since zero-energy buildings are limited to a maximum of less than 2 storeys in Nordic climates and 3 in Mediterranean climates.In this particular historical period, the outlined results take on considerable relevance, as the highlighted feasibility limitations could jeopardise the implementation of zero emission targets, but they can also be used to properly orient energy policies under development.

Multi-objective coordinated optimization of low-carbon building energy systems based on high renewable energy penetration

In the context of China's targets to achieve a "carbon peak" by 2030 and "carbon neutrality" by 2060, the operation and maintenance of buildings with low-carbon and zero-energy consumption emerge as a critical technology for accomplishing the "dual carbon" goals in the building sector. As a novel energy supply system, low-carbon building energy systems can provide low-carbon, efficient, and economical energy supplies. Accordingly, this paper initially constructs a low-carbon building energy system based on a high penetration of renewable energy sources. Subsequently, considering the benefits of economic efficiency, carbon emissions, and renewable energy utilization, a multi-objective cooperative optimization model for low-carbon building energy systems with high renewable energy penetration is established. Finally, a multi-objective particle swarm optimization algorithm is applied to solve the model, and the system is studied and analyzed using a large domestic park as a case study. The results indicate that the low-carbon building energy system with high renewable energy integration, aiming for economic efficiency, carbon reduction, and increased renewable energy consumption, achieves supply energy costs of $ 19.2/m2 and carbon emissions of 49.1 kg/m2. These values represent reductions of $ 7.4/m2 and 60.9 kg/m2 compared to separate supply systems. Lastly, the study of the low-carbon building energy system provides theoretical references for renewable energy integration and energy transition in the building sector.

A two-year dataset of energy, environment, and system operations for an ultra-low energy office building

This paper describes a two-year high-fidelity dataset for an ultra-low energy office building and living laboratory called HouseZero®. The building integrates multiple low-energy technologies, such as natural ventilation with automatic windows, ground source heat pump, and thermally activated building systems. The building’s performance is continuously monitored with an extensive sensor network. The dataset consists of breakdown energy end uses, photovoltaic (PV) production, zone-level indoor environment including indoor air temperature, CO2 concentration, and relative humidity, micro-climatical conditions, building façade temperature, and detailed system operations including zone-level BTU meter, valve status, slab temperature, window/skylight opening status, heat pump, and geothermal well operations. The data can be used to support data analytics of ultra-low-energy building operations, and data-driven modeling of low-energy building systems.

Importance of Window Installation in Residential Building Envelopes Having Continuous External Insulation in Order to Realize Energy Efficiency

Residential buildings are one of the prime candidates in the United States for reducing energy consumption. Continuous exterior insulation (CEI) is being used increasingly often in residential buildings to improve energy efficiency. Windows constitute 15–40% of a building envelope and are the weakest component in energy performance. The installation of windows in walls with CEI has not been well evaluated. We identified four cases of installing windows in walls with CEI of 25–76 mm (1–3 in.) thickness and analyzed the energy loss between the window and wall interface (flanking loss), structural issues, air leakage, and moisture penetration. Thermal analysis showed that the insulation value (RSI) of the 305 mm (12 in.) perimeter wall surrounding a window decreased by 7.6–34.5% in the four cases when compared with the RSI of the wall without the window. A window installation method is proposed to address the issues likely to occur with installation methods currently being used in the field. An out-of-the-box installation system was also designed to achieve a better thermal performance, cost effectiveness, and structural performance in high-performance residential buildings.

Research on the influencing factors and countermeasures of the development of prefabricated buildings under the background of "double carbon"

As a representative of green and low-carbon buildings, prefabricated buildings have gained widespread attention from the government and industry due to their significant advantages in energy conservation and emission reduction, time saving, labor saving, and high construction efficiency. However, currently, prefabricated buildings have a low market share in China and their development is slow. This article summarizes the influencing factors of the development of prefabricated buildings and constructs a causal model (FCM model) consisting of five conceptual nodes for inference and simulation analysis. The predictive analysis results show that the correlation strength between the four major influencing factors and the development of prefabricated buildings is: F2(cost environment）> F4（policy system）> F3（technology system）> F1(market foundation). This article proposes reasonable measures and suggestions based on the analysis results, providing reference for promoting the development of prefabricated buildings.

Optimization design of low-carbon building thermal energy based on optical sensing and virtual reality image scene reconstruction

With the intensification of global climate change and energy crisis, the design of low-carbon buildings has gradually become a research hotspot in the field of architecture. Effective thermal optimization design not only reduces energy consumption, but also improves the comfort and sustainability of the building. This study aims to explore the optimization design of low-carbon building heat energy based on light sensing technology, combined with virtual reality image scene reconstruction, to provide an innovative design method to achieve intelligent management and optimization of building heat energy. Through the introduction of light sensing technology, the light intensity and heat distribution inside and outside the building are monitored, and the combination of data analysis and model simulation is used to evaluate the heat use of the building. On this basis, virtual reality scenes are constructed to reconstruct the heat flow and distribution of buildings, providing designers with intuitive visualization tools. The research shows that the design method based on light sensing can effectively identify the areas of heat waste in the building, and reduce the energy consumption of the building by optimizing the window layout, adding greening and improving the thermal management system. Virtual reality image scene reconstruction makes the design process more intuitive, helps the design team to quickly adjust and optimize, and improves the efficiency and accuracy of the design.

Mitigating operational greenhouse gas emissions in ageing residential buildings using an Urban Digital Twin dashboard

With the increasing stock of ageing infrastructure and resource constraints in Singapore, related risks and carbon emissions can be mitigated through long-term resilience planning, automated building inspection, and effective maintenance. Sustainable actions are needed to maintain Singapore's ageing infrastructure. Hence, a state-of-the-art control and management system is required in the form of smart city digital tools. We introduce an Urban Digital Twin (UDT)—GHG App for decision-makers in Singapore's operational building greenhouse gas (GHG) emission mitigation and decarbonisation initiatives. Based on multiple-criteria decision analysis (MCDA), a Potential for Intervention (PFI) map was created to rejuvenate the building system. Decision-makers can use this map to prioritise the rejuvenation of low-carbon building systems in the built environment. A heat map of the PFI results highlights which buildings need urgent rejuvenation based on critical parameters. The GHG App utilises this method to generate maps and enables users to modify parameter weights based on their priorities, automatically updating the map. Users can plan an intervention for buildings with higher PFI values once the map is generated. The GHG App provides interactive data visualisation of 119,872 features representing Singapore's built environment, including the context size of 6,785 existing residential buildings modelled and used to demonstrate the analysis results. Our research findings can contribute to the development of standards for accounting for operational GHG emissions, setting emission limits, and planning decarbonisation in the built environment sector.

Synergistic modification of hydrolyzed keratin-based rigid polyurethane foam with zinc stannate and aluminum hypophosphite to improve its thermal stability and flame retardant properties

Abstract Zinc stannate (ZS) was prepared for flame retardant modified rigid polyurethane foam (RPUF). The flame retardancy and thermal stability performance of the modified RPUFs were investigated by limiting oxygen index (LOI), cone calorimeter (CONE), smoke density (Ds) test and thermogravimetric (TG) differential thermal analyzer. The LOI of RPUF5-7.5 AL/7.5 ZS with 5 wt% hydrolyzed keratin (HK), 7.5 wt% aluminum hypophosphate (AL) and 7.5 wt% ZS increased from 26.1 % to 27.2 %. At 50 kW/m2 radiant intensity, RPUF5-7.5 AL/7.5 ZS had the lowest peak heat release rate (PHRR) and heat release rate (THR), which were 108.17 kW/m2 and 2.56 MJ/m2, respectively. In addition, RPUF5-7.5 AL/7.5 ZS had the highest initial decomposition temperature of 191.24 °C and the largest activation energy (E) of 148.16 kJ/mol. Under flameless condition, the maximum Ds of RPUF5-7.5 AL/7.5 ZS was 31.25, and its light transmittance was also the highest, i.e., 57.89 %. Therefore, ZS/AL was selected as a synergistic flame retardant system to modify the RPUF, and promotes the development of high-performance building materials.

Heat insulation and thermal insulation method of passive low energy consumption residential building exterior envelope structure based on BIM

With the improvement of economic level, a continuous rise in building energy consumption brings about serious environmental problems. Therefore, this study proposes a passive energy-consuming residential building envelope thermal insulation and heat preservation method based on building information modeling technology for building energy consumption increasing and envelope structure's performance improving. Firstly, it is a study on the passive low-energy residential building envelope's thermal insulation materials and architecture, and secondly, it is a study on the improvement of the thermal insulation and heat preservation performance of the passive low-energy residential building envelope on the foundation of building information modeling. These experimental results show that in the residential building, the indoor temperature averages around 27.8 °C, of which the highest indoor ambient temperature is found at 21 o'clock, with a temperature value of 28.4 °C, which reduces 2.1 °C when comparing with the indoor temperature under the traditional residential building. Under the exterior wall construction utilizing this technology, the temperature change of the indoor environment is smoother, which satisfies people's requirements for the indoor living environment. At the same time, the area parameters of the ventilation area of the building and the area of the envelope obtained after the analysis of BIM technology have a significant effect on the cooling of the interior. This method reduces the use of resources and lays a good foundation for the further development of building informatization, which is significant in realizing the informatization developing in construction.

Integrating vertical farm into low-carbon high-rise building in high-density context: A design case study in Hong Kong

Today's world faces multiple challenges, including climate change, biodiversity loss, and food security. In addition, in the post-pandemic era, there is an urgent need to re-design urban habitats to reduce the epidemic's enduring impacts and reconnect citizens with healthy community activities. As a city with the top population density level in the world, Hong Kong is home to many high-rise communities. This article took the architectural design competition “Green Tower Hong Kong” as an entry point to discuss the technical feasibility and design strategies of integrating high-rise residential buildings with urban agriculture to improve urban food security, enhance on-site solar energy utilization, and develop a sustainable residential environment conducive to low-carbon living and working. The issue of how to improve the dietary structure of Hong Kong residents and reconnect them through space design was focused. Finally, taking the site of Kwun Tong Center as the case study, a resilient residential high-rise building integrated with shared gardens and greenhouses was proposed with a technical-oriented methodology and optimization framework. The final design of mixed-use buildings can provide apartments for 2500 individuals, produce 340,750 kg of vegetables with 156 % self-sufficiency, and generate electricity of 1,080,000 kWh annually. This paper examines strategies for integrating urban agriculture into high-rise residential buildings in high-density urban environments. It proposes a technology-based design optimization method, offering a reference for future explorations of low-carbon, resilient communities.

Aluminium Hydroxide/Graphene-reinforced Rigid Polyurethane Foam Hybrid Composites

In this study, rigid polyurethane foams (RPUF) were successfully modified using 30 wt.% aluminium hydroxides (ATH), 1.0 pphp silicone surfactant, and different concentrations of graphene, using a one-shot one-step foaming method. This study aims to improve the compressive strength, flame retardancy, and thermal properties of RPUF by creating a synergistic effect between ATH and graphene in fire-retardant RPUF hybrid composites. The effects of a fixed amount of ATH and silicone surfactant and various loadings of graphene on RPUF were investigated. The results show that 0.5 wt.% graphene loading confers the best compression performance on the hybrid composite. Their compressive strength value of 12.58 KPa was higher than virgin RPUF (4.07 KPa) and RPUF/ATH (9.89 KPa). FTIR confirmed the functional groups in the virgin RPUF but could not identify new functional groups in most modified composites. The smallest amount of graphene addition (0.5 wt.%) produced a more stable hybrid composite structure. At 3.0 wt.% graphene addition, the maximum decomposition temperature of the RPUF/ATH hybrid composite was recorded (539oC), which was enhanced by 50% compared to virgin RPUF (296oC), and the highest char residue of 17.46% was observed. The incorporation of graphene enhanced the thermal firmness of the hybrid composite. The study also revealed an enhancement in the fire resistance of the hybrid composite. The LOI and UL-94 results showed that incorporating 3.0 wt.% enables increased LOI value and V-0 classification compared to virgin samples. This hybrid composite can be used in high-performance building insulation applications.

Simulation of low energy building thermal energy cycle in IoT smart city planning based on environmental sensors and deep learning

With the intensification of global climate change, the reduction of building energy consumption has become an important goal of smart city development. By optimizing the thermal energy circulation system, low energy buildings can not only reduce energy consumption, but also improve living comfort. In recent years, with the help of environmental sensors and deep learning technology, the intelligent management of building heat energy cycle has become a research hotspot. The research constructs an intelligent thermal energy circulation system that integrates multiple environmental sensors for real-time monitoring of indoor and outdoor temperature, humidity and other key environmental parameters. A deep learning algorithm is used to analyze the collected data to optimize the control strategy of the thermal energy cycle. Through simulation, the energy efficiency performance of the scheme under different climatic conditions and building types was evaluated. The experimental results show that the control strategy based on environmental sensors and deep learning can significantly improve the thermal energy utilization efficiency of low-energy buildings, and the average energy consumption is greatly reduced compared with the traditional management mode. The system shows good adaptability and stability under different climate conditions. Therefore, the application of environmental sensors and deep learning technology in the thermal energy cycle of low-energy buildings can effectively promote the energy efficiency management of smart cities.

Assessment of building design strategies to enhance energy efficiency and thermal comfort: Case study in Morocco’s climate zones

Energy efficiency in the context of building design is a significant concern in Morocco. This paper offers a comprehensive analysis of how various design variables can impact both energy consumption and thermal comfort in the Moroccan context. Rather than isolating individual design variables, we investigate synergistic combinations of these variables. To achieve this, we develop multiple building design scenarios, each employing different combinations of design options, focusing on building orientation, window-to-wall ratio, building envelope construction, and window shading. We use EnergyPlus to conduct energy simulations for all scenarios under the hypothesis of air-conditioned houses and free-running houses with and without natural ventilation. Our results reveal that building design has the potential to significantly enhance energy efficiency and thermal comfort, but not for the same design strategies. In comparison to the most energy-efficient design scenario, the least favorable design scenario can lead to an increase in energy consumption between 237% in Agadir and 130% in Ifrane. Meanwhile, design scenarios favoring comfort can increase the number of comfortable hours by 85% in Agadir and 59% in Ifrane. We identify optimal building design scenarios that simultaneously offer the highest comfort levels with the lowest energy requirements. The findings provide valuable guidance for architects, allowing them to design high-performance buildings in all climate zones in Morocco.

Study on mechanical properties and damage mechanism of alkali-activated slag concrete

The cement industry has become one of the important sources of greenhouse gas emissions, and the alkali-activated slag (AAS) has the same mechanical properties and lower carbon emissions as cement in the production process. Therefore, it can be used as an alternative binder for low-carbon buildings. The effect of alkali concentration (mass ratio of Na2O to binder) on the macro-mechanical properties and meso-damage mechanism of alkali-activated slag concrete (AASC) under uniaxial compression was investigated in this work. Six kinds of concrete with alkali concentration of 2 %, 4 %, 6 %, 8 %, 10 % and 12 % were prepared. The microscopic characteristics of AASC were characterized by nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), x-ray diffraction (XRD) and x-ray energy dispersive spectroscopy (EDS); the meso-damage evolution mechanism of AASC was discussed by statistical damage theory. The results showed that the peak stress and elastic modulus of AASC specimens increased, and the microstructure became denser with the increase of alkali concentration. However, the mechanical properties of the specimen deteriorated to some extent when the alkali concentration exceeded 6 %; for example, the peak stress decreased by 24.00 MPa when the alkali concentration was increased from 6 % to 12 % at the age of 28d. Based on the statistical damage theory, the effective stress concept was introduced to quantitatively analyze the mesoscopic damage evolution of AASC. Both fracture and yielding damage modes were considered. By exploring the regular changes of the mesoscopic parameters, the connection between the macroscopic mechanical properties and the mesoscopic damage mechanism was established. Based on the above mechanical properties and mesoscopic damage results, the alkali concentration of 6 % can be used as the best mixture proportions of AASC.

Preparation and characterization of micro-cellular melamine foam supported SiO2 aerogel for building thermal insulation

This study aims to complement the advantages of SiO2 aerogel and melamine foam (MF) to produce high-performance building insulation materials. The optimal sol–gel scheme was determined by controlling system temperature, water content, amount of ethanol and amount of acid-base catalyst (orthogonal experiment). The density and porosity of MF/SiO2 aerogel were regulated by adjusting aging time, aging temperature and type of aging agent. Furthermore, the effects of different volume fractions hydrophobic modifier on the surface free energy and wettability of MF/SiO2 aerogel were also investigated. The experiment results showed that the prepared MF/SiO2 aerogel satisfies requirements for low density (0.089 g/cm3), low thermal conductivity at room temperature (0.0256 W m−1·K−1), and excellent hydrophobic performance (the contact angle was 140.1°). Meanwhile, it was found that SiO2 aerogel was stably and uniformly distributed in the pores of the MF and effectively enhanced the mechanical property (a maximum compressive strength of 0.2058 MPa), heat-shielding performance, flame retardant property, and sound absorption capacity(αmax = 0.76, αave = 0.31).Therefore, the MF/SiO2 aerogel composites exhibit exceptional application potential in comparison to conventional building insulation materials (such as EPS, Rock wool board, etc.) due to their significantly low thermal conductivity and remarkable flame retardant properties.

Intermittent demand-controlled ventilation for energy flexibility and indoor air quality

Buildings play a crucial role in ensuring power grid stability by providing energy flexibility. Existing research mainly improves the building energy flexibility through energy storage, but requires additional equipment costs. This study proposes a new source of building energy flexibility by properly managing indoor air quality with intermittent demand-controlled ventilation (iDCV), which requires no additional equipment investment. This study reveals the mechanisms of enhancing energy flexibility and develops a nonlinear programming algorithm to optimize the dynamic operation of the iDCV. The robustness of the proposed iDCV in enhancing energy flexibility is verified under different application scenarios in different climate zones. The results show that compared with the existing method, the proposed iDCV enhances the energy flexibility with a peak load reduction of 17.1 %–36.1 % under the scenario of constant electricity price and with a flexibility factor enhancement of 9.5 %–80.8 % under the scenario of time-of-use electricity price. Besides the benefit to the power grid with the enhanced energy flexibility, the proposed iDCV also delivers benefits to building users with energy savings of 19.6 %–22.0 % and cost savings of 21.5 %–26.1 %. Therefore, the proposed iDCV provides dual benefits for both the power grid and building users and contributes to developing energy-flexible, low-carbon, and healthy buildings.

Technology for Automated Production of High-Performance Building Compounds for 3D Printing.

Three-dimensional printing technology in construction is a rapidly growing field that offers innovative opportunities for design and construction execution. A key component of this process is the automated production of high-performance construction mixtures that meet specific requirements for strength, fluidity, and setting speed. This overview article outlines the history and development of 3D printing technology in the construction industry, describes various printing technologies, and discusses the properties and requirements for construction mixes. Special attention is given to automated systems for batching and mixing ingredients, which increase the precision and efficiency of production. The different types of construction mixes used in 3D printing and the main technical and operational challenges associated with their application are also presented. The article's conclusions highlight the potential of this technology to revolutionize the construction industry by improving efficiency and reducing costs and project lead times.