Unit Floor Area Research Articles

Effects of solar energy absorbed by south wall on carbon emission from space heating in hot summer-cold winter region

Carbon emission caused by space heating (CEH) in hot summer and cold winter climate zone has increased dramatically. Taking advantage of the solar energy absorbed by south wall (SEASW) can effectively reduce CEH, however, the accurate quantification of its impact remains a challenge. The study investigates the potential of SEASW in mitigating CEH. Key parameters affecting CEH, such as sunny day ratio, insulation form, and outer surface heat transfer coefficient of south wall (h), were analyzed. Results show the reduction in carbon emissions caused by the solar energy absorbed by each unit area of the south-facing wall (ΔCreduction) can be as high as 18.61 kgCO2⋅m−2 for the wall employing internal insulation and smaller h. A prediction model of ΔCreduction was further developed by using multivariate nonlinear regression, which can estimate the reduction in CEH for different fuels as heating source by a south wall in different sizes. Besides, the potential of SEASW on the reduction of carbon emission per unit floor area can reach 12.2 %. This study underscores the importance of SEASW as a carbon-neutral heating strategy, particularly for regions characterized by short winter heating periods and lower heating loads compared to colder climates. It provides valuable insights for sustainable energy practices and policy formulation.

Advancing cost-optimal residential decarbonisation pathways: An examination of heat pumps and thermal efficiency

In Ireland, residential energy policy has been influenced by thermal inefficiency, high electricity prices and energy poverty. These factors have driven the fabric-first approach, where buildings must undergo extensive thermal retrofitting to qualify for heat pump subsidies. The cost-effectiveness of this approach has not been properly scrutinised to date. This paper addresses this knowledge gap by exploring the cost-effectiveness of the fabric-first approach and other decarbonisation strategies for the residential sector and broader energy system. The study develops scenarios by modifying the Heat Loss Indicator (HLI) threshold, which evaluates the fabric and ventilation heat loss per unit of floor area and is used to determine heat pump subsidy eligibility. The paper also considers scenarios that permit installing sub-optimal performing heat pumps that do not achieve peak performance levels in dwellings with higher HLIs. The analysis uses the TIMES-Ireland Model (TIM), a model of the whole energy system that reflects the interdependence of mitigation pathways across different energy sectors. Our study shows that Ireland's fabric-first approach requires 22 times more thermal retrofits to meet climate targets than alternative pathways. The alternative pathways based on the latest heat pump performance data are more cost-effective, showing that higher heat pump HLI thresholds can reduce the average sectoral marginal CO2 emission price by 60% compared to the current fabric-first approach. The cost savings indicate that shifting to an HLI threshold of 2.3 W/K/m2 is close to optimal, while cost savings are minimal when moving from an HLI of 2.3 to 3 W/K/m2. Furthermore, electricity prices and household awareness are essential to the cost-optimal transition to residential heat pumps.

The potential use of mass timber in mid-to high-rise construction and the associated carbon benefits in the United States.

Nonresidential and mid- to high-rise multifamily residential structures in the United States currently use little wood per unit floor area installed, because earlier building codes lacked provisions for structural wood use in those types of buildings. However, revisions to the International Building Code allow for increased wood use in the form of mass timber, as structural and fire safety concerns have been addressed through new science-based design standards and through newly specified construction materials and measures. This study used multiple models to describe alternative futures for new construction, mass timber adoption rates, and the associated carbon benefits in higher than three-story buildings in the United States. The use of mass timber, in place of traditional constructions (i.e., structures dominated by concrete and steel), in projected new higher than three-story buildings was shown to provide combined carbon benefits (i.e., global warming mitigation benefits), including avoided embodied carbon emissions due to the substitution of non-wood alternatives and additional biogenic carbon storage in mass timber materials, of between 9.9 and 16.5 million t CO2e/yr spanning 50 years, 2020 to 2070. These carbon benefits equate to 12% to 20% of the total U.S. harvested wood products carbon storage for 2020. Future research is needed to understand how greater mass timber adoption leads to changes in forest product markets, land use, and total forest sector carbon.

Morphology Optimization of Residential Communities towards Maximizing Energy Self-Sufficiency in the Hot Summer Cold Winter Climate Zone of China

Further research is needed on the capability of residential communities to achieve energy self-sufficiency under the constraints of current standards of land use, in particular for the Hot Summer and Cold Winter climate zone (HSCW) of China, where the majority of communities are dominated by high floor-area ratios, thus high-rise dwellings, namely less solar potential per unit floor area, while most residents adopt a “part-time, part-space” pattern of intermittent energy use behavior, thus using relatively low energy per unit floor area. This study examines 150 communities in Changsha to identify morphological indicators and develop a prototype model utilizing the Grasshopper platform. Community morphology is simulated and optimized by taking building location, orientation, and number of floors as independent variables and building energy consumption, solar PV generation, and energy self-sufficiency rate as dependent variables. The results reveal that the morphology optimization can achieve a 4.26% decrease in building energy consumption, a 45% increase in PV generation, and a 13.2% enhancement in energy self-sufficiency, with the optimal being 39%. It highlights that energy self-sufficiency cannot be achieved solely through morphology improvements. Moreover, the study underscores the crucial role of community orientation in maximizing energy self-sufficiency, with the south–north orientation identified as the most beneficial. Additionally, a layout characterized by a horizontally closed and staggered pattern and a vertically scattered arrangement emerges as favorable for enhancing energy self-sufficiency. These findings underscore the importance of considering morphological factors, particularly community orientation, in striving towards energy-self-sufficient high-rise residential communities within the HSCW climate zone of China.

Historical peak situation of building carbon emissions in different climate regions in China: Causes of differences and peak challenges

The climatic conditions in different regions of China are complex and diverse, and the characteristics of building energy consumption in different climatic regions are quite different, leading to significant differences in the historical peak situation of building carbon emissions (BCE). Based on the statistical Mann–Kendall (MK) trend test method, this study evaluates the historical peak situation of BCE in different climate regions in China and discusses the reasons for the differences in the growth trends and peak situations of BCE in these regions. Furthermore, according to the characteristics of building energy consumption in different climate regions, the challenges faced by each climate region in promoting the peaking of BCE are highlighted. The research results show that owing to the continuous increase in the proportion of electrification and clean energy power generation, the electricity emission factor and carbon emissions per unit of energy consumption continue to decline, and the growth rates of BCE in the transitional and southern regions are significantly lower than the growth rate of building energy consumption, and the carbon emissions per unit floor area in the southern region has reached its peak. The main obstacles to promoting the peaking of BCE in the northern heating region are the high‑carbon heating energy structure and the unrestrained heating behavior of residents, while the challenges faced by the transitional and southern regions are the southward migration of the population and economic centers of gravity and the gradual increase in residents' requirements for living environment comfort. Government decision-makers should formulate differentiated BCE peaking strategies according to the characteristics of building energy consumption in different climate regions.

RC建物の地震時の損傷が発生させる労務量と層間変形角の関係性に関する基礎的研究

In order to evaluate repairability (i.e., repair time and repair cost, etc.), it is necessary to estimate the amount of labor (person-day) for repair caused by seismic damage. The purpose of this study is to obtain the fundamental information necessary for establishing the relation model between the labor amount L per unit floor area and the inter-story drift angle R (i.e., L-R model). We analyze the effects of the amount of structural and non-structural components and the failure mode of the structural members, on the L-R relation, and discuss the feasibility of establishing a L-R model for repairability evaluation.

Assessment and driving factor of housing vacancies in Shandong Peninsula urban agglomeration based on multi-source remote sensing data

As the urbanization rate in the world has increased rapidly, the housing vacancy problem has become serious and attracting more attention. Calculating and analyzing vacant housing can help reduce the wasteful use of resources. This paper measures the housing vacancy rate and housing vacancy stock in the Shandong Peninsula urban agglomeration using night-time lighting and land use data. The results show that the average housing vacancy rate in the Shandong Peninsula urban agglomeration rose rapidly from 14.68% in 2000 to 29.71% in 2015 before declining slowly to 29.49% in 2020. Since urban population growth is lower than the housing construction rate, the average annual growth of housing vacancy stock between 2000 and 2020 exceeds 3 million square meters in megacities and is around 1–2 million square meters in large and medium-sized cities. The vacant housing has caused considerable waste of housing resources. The driving factors of the housing vacancy were further analyzed using the LMDI decomposition method. Results indicate that the economic development level is the most significant driving factor of the vacant housing stock. In addition, the value effect of unit floor areas is the major driving factor inhibiting the growth of vacant housing stock, while the decline of unit floor area value is conducive to the reduction of this stock.

Performance assessment of the integration of semitransparent solar cells with different geometry of greenhouses under different climate regions

A lack of resources and suitable farming lands, climate change, and a rapidly growing population are some of the main concerns of the societies that pose security challenges to the governments. Creating controlled environments for cultivation, growing plants, and farming, such as greenhouses, may assist in overcoming these challenges. Greenhouses can significantly increase land use efficiency in agriculture by increasing crop yield and harvesting throughout the year, which has long been proven effective. The history of greenhouses for farming dates back to Roman times, and there are different barriers to their applications. An example is the provision of energy to control the cultivation conditions of plants in greenhouses, particularly for heating and cooling hot and cold climate areas. On the other hand, based on the global energy trend, decentralized energy production based on solar energy is highly regarded. In the same way, that households can harvest solar energy, greenhouses can also benefit from solar energy. However, because greenhouses need sunlight to cultivate plants, reducing sunlight using common photovoltaic panels is not logical. By incorporating semitransparent solar cells into these greenhouses, the issue of reduced sunlight could be addressed, and further efficiency gains could be achieved by reducing energy demand in these greenhouses. This research investigates the energy supply system's integration with greenhouses consumption. First, we assess different conventional types of greenhouses in terms of energy demand. Then, we investigate the energy demand with organic photovoltaic (OPV) integration for each type. Finally, the best design of the greenhouse for OPV integration is recommended. Results show that flat arch geometry is the best choice for dry and cold climates, while sawtooth geometry showed better improvements in tropical climates. In both temperate/mesothermal and continental/microthermal climates, A-frame geometry showed superiority in energy saving. Simulations revealed an annual electricity generation for a unit floor area of the greenhouses to be 173.7 kWh/m2 to 247.9 MWh/m2 for the optimum structural geometries that decrease the energy consumption of greenhouses. Additionally, the results show that the installation of the OPV can decrease energy consumption from 15 to 58% based on the greenhouse's location and structural geometry.

Interprovincial differences in the historical peak situation of building carbon emissions in China: Causes and enlightenments

Scientific assessment of the historical carbon peak situation of provincial buildings in China is the premise and basis for understanding the country's development trends and formulating carbon peak goals. The population size, urbanization stages, economic development levels, natural resources endowment, and energy structure characteristics vary significantly for the different provinces in China, resulting in significant differences in the peaking situation of building carbon emissions (BCE). The differences require more attention given the current environmental status. Based on the judgment function of carbon peaking conditions and the statistical Mann-Kendall (MK) trend test method, this study evaluates the historical peak situation of building carbon emissions at the provincial level in China. The peaking sequence of BCE, building carbon emissions per capita (BCEP), and carbon emissions per unit floor area (BCEA) were analyzed, and the driving factors that cause different carbon peak situations were discussed. Further, with reference to the experience of the United States, a peak strategy for building carbon emissions in China was proposed. The research results showed that BCE in Beijing and Yunnan have peaked, and the three provinces of Shanghai, Sichuan, and Hubei have plateaued. The most important factors that cause different peaking situations for BCE are the floor area per capita and carbon emissions per unit of energy consumption. In addition, the peak order of building carbon emissions was BCEA, BCEP, and BCE. A strategy that should be adopted in the promotion of buildings' carbon peak in China is to formulate phased peak goals for BCE, BCEP, and BCEA at a national level and differentiated echelon peak goals at a provincial level considering interprovincial differences. This study provides a scientific basis and decision-making reference for formulating a path to buildings' carbon peak at a provincial level in China.

Thermal performance of a directional heat radiation device utilizing the Monte Carlo ray tracing method

Conventional air conditioning systems heat and cool an entire space for the total volume but are deficient in terms of energy efficiency. Partial and personalized devices rarely take into account moving occupants and are deficient in terms of flexibility. To address these problems, a directional heat radiation (DHR) device was introduced. The effectiveness of the DHR device under heating conditions was verified by experiments and the thermal performance of the DHR device under three different arrangements was analyzed. Based on energy balance, the radiation distribution factor calculation model and the heat transfer model of the DHR device were established by combining the Monte Carlo ray tracing method and the thermal network method. The results showed that the thermal performance of the DHR device arranged level downward was best and twice that of the level upward arrangement. The mathematical model of the heat transfer process was verified by experimental data, and the relative error was within 2 %. The simulation results showed that the radiation temperature at different positions θdprt in the center of the room increased with increasing tube diameter and reflecting cover opening width and decreased with increasing tube spacing. Under simulated heating conditions, the optimal structure of the DHR device has a tube diameter of 16 mm, reflecting cover opening width of 60 mm, and tube spacing of 80 mm. The heat flux per unit floor area of the DHR device was approximately 56 W/m2, which reduced the heating capacity by 20 % compared to that without the reflector cover, while improving the local thermal environment of the space and increasing energy efficiency.

COMPARATIVE CARBON-FOOTPRINT ANALYSIS OF RESIDENTIAL BUILDINGS WITH DIFFERENT STRUCTURAL MATERIALS

An important step towards achieving sustainability goals in the construction sector is taken by developing solutions that adopt ‘greener’ structural materials for buildings. This paper establishes a comparison among four existing residential buildings in Sweden, that utilize different structural solutions, in terms of their global warming potential (GWP). The structural solutions compared are prefabricated reinforced concrete (RC), light timber frame, cross-laminated timber (CLT) panels, and CLT modular construction. For each building, a life cycle assessment (LCA) was performed to estimate the greenhouse gas (GHG) emissions attributable to material production. In general, the results of this study revealed climate benefits associated with timber-based construction, with approximately 50% savings on average in the GHG emissions per unit floor area of the buildings as compared to prefabricated RC construction. Finally, this effort demonstrates the significance of the structural material choice on the overall carbon footprint of a building, especially at the production stage.

COMPARATIVE CARBON-FOOTPRINT ANALYSIS OF RESIDENTIAL BUILDINGS WITH DIFFERENT STRUCTURAL MATERIALS

An important step towards achieving sustainability goals in the construction sector is taken by developing solutions that adopt ‘greener’ structural materials for buildings. This paper establishes a comparison among four existing residential buildings in Sweden, that utilize different structural solutions, in terms of their global warming potential (GWP). The structural solutions compared are prefabricated reinforced concrete (RC), light timber frame, cross-laminated timber (CLT) panels, and CLT modular construction. For each building, a life cycle assessment (LCA) was performed to estimate the greenhouse gas (GHG) emissions attributable to material production. In general, the results of this study revealed climate benefits associated with timber-based construction, with approximately 50% savings on average in the GHG emissions per unit floor area of the buildings as compared to prefabricated RC construction. Finally, this effort demonstrates the significance of the structural material choice on the overall carbon footprint of a building, especially at the production stage.

Understanding the energy consumption of information and communications equipment: A case study of schools in Taiwan

Information and communications technology (ICT) equipment is often used to help conserve energy, but such equipment also requires energy to operate. This study investigated the energy consumption of ICT in 28 secondary schools (SSs) and 98 elementary schools (ESs) in Taiwan. The average annual energy consumption of ICT equipment is 28,162 kWh and 20,888 kWh per SS and ES, respectively; per unit floor area, this is estimated to be 60.5 and 27.5 Wh/m2/year, respectively. ICT accounted for 7.3%–7.7% of the total energy consumption of each school. Projection, computer, and network equipment together account for more than 90% of the total electricity consumed by ICT equipment. The total energy consumption of ICT equipment is positively correlated with school type and size. The study established three multiple regression models to investigate the total energy consumption of ICT equipment per school, per class, and per student, and the models all exhibited statistical significance. The energy consumption is highly correlated with usage time and power dissipation. Equipment procurement and energy consumption management play key roles in the energy conservation. This study may serve as references for school administrators evaluating energy conservation effectiveness.

소형 주택의 창면적비에 따른 냉방 및 난방 에너지 소요량과 시공비용 연구

As the global warming problem becomes more serious, the Korean government is putting considerable effort to reduce primary energy consumption and carbon generation by implementing relevant policies. In this study, a small-scale house with a floor area of 114.51 m2 located in Yangpyeong, Gyeonggido, Korea was selected to study the effect of window wall ratio on cooling and heating energy consumption, energy cost, and construction cost. Cooling and heating loads and energy consumption in consideration of the window design were analyzed using PHPP, an energy balance, and a passive house planning tool. The height of the east side window was fixed at 3.89 m, while the width was changed to the present Base and two alternative designs. The window areas were 18, 12, and 6 m2 for Base, ALT-1, and ALT-2, respectively. Temperature, humidity, and infiltration were measured for PHPP input values. When the window areas were reduced by 33% and 67% relative to the Base, cooling and heating energy per unit floor area were reduced by only a small amount. Similar results were obtained for heating and cooling energy costs. Our findings indicated that adopting ALT-2, the design with the least window area can reduce the construction cost by 8.5% or 7.764 million won. Therefore, unlike for the energy consumption, much higher construction cost reduction can be achieved with a small window area. This is expected to have a significant impact on the facade design according to the client

МАТЕМАТИЧНЕ МОДЕЛЮВАННЯ ОПТИМІЗАЦІЇ ПОКРИТТЯ КРУГЛОЇ У ПЛАНІ БУДІВЛІ З РАДІАЛЬНИМ РОЗТАШУВАННЯМ БАЛОК

The article presents the results of optimization of the angle between radial beams in the floor of a circular building in the plan. On the one hand, they rest on the central post, and on the other, on vertical supporting structures along the circle. Steel decking is laid on the beams. The angle between the beams is determined so that the mass of the beam and the deck is minimal. This angle is considered optimal. To solve the problem, the target function of the cost of flooring and radial beams per unit floor area is used. This function depends on the angle between the beams. Using mathematical methods of differentiation, the minimum of the objective function and the corresponding value of the optimal angle were found. The thickness of the flooring was determined on the basis of ensuring its rigidity. It is assumed that composite welded radial beams have I-beams with two axes of symmetry. The height of the beam corresponds to the equality of the areas of the shelves and the wall. The problem of determining the optimal angle between the beams was solved on the basis of ensuring the strength of the beams under normal stresses. In the design diagram of the beam, a triangular distributed load is adopted. The dimensions of the cross-section of the beam were determined based on the equality of the required and actual moments of resistance, and were included in the target cost function. The study took into account that the deflection of the beam at the optimal angle between them can exceed the limiting standard value. Based on the solution of the system of equations of strength and stiffness, a formula is obtained for the minimum angle between the beams from the stiffness condition. The carried out mathematical studies have shown that at the optimal angle between the beams, it is possible to ensure its rigidity. This is possible when the flexibility of the beam wall exceeds a certain minimum value. Analysis of the formula for the minimum value of the wall flexibility showed that it is proportional to the design steel resistance to the sixth power. Therefore, to ensure that the deflection of the beam does not exceed the limiting value at the optimum angle, it is necessary to use low strength steel. To confirm the practical feasibility of using the proposed method, the problem was solved with certain numerical data. The results obtained have confirmed that the problem has a practical meaning at a relatively low steel strength. In addition, it turned out that the optimal angle between the beams does not depend on its span.

Simulation and optimization of night cooling with diffuse ceiling ventilation and mixing ventilation in a cold climate

Accurate convective heat transfer coefficient (CHTC) is crucial to assess the night ventilation performance accurately. Previous experimental studies proposed CHTC correlations tailored for night cooling with diffuse ceiling ventilation (DCV) and mixing ventilation (MV). A holistic approach integrating the building energy simulation and optimization method was put forward to validate the experimentally proposed correlations, simulate and optimize the performance of night cooling with DCV and MV. The validation results demonstrated that the proposed correlations predicted the surface temperatures accurately with a maximum mean absolute error of 1.9 °C. For a typical air-conditioned office room, night cooling with DCV saved about 0.2 kWh/m2 total cooling energy per unit floor area (TCEC) more and provided a lower average predicted percentage of dissatisfied during the working hours (aPPD) by up to 3.1% than that with MV. Compared with the validated correlations, the empirical ceiling diffuser convection algorithm overestimated the night energy-saving potential by up to 0.5 kWh/m2 (13.8%) and yielded a maximum difference in the aPPD of 1.5%. Optimization significantly saved TCEC by 1.1 kWh/m2 (29.0%) for DCV and 0.9 kWh/m2 (25.7%) for MV while maintaining the aPPD within 10%, compared to respective base cases.

Thermal Characteristics and Parametric Analysis of an Improved Solar Wall

Solar air collectors installed on buildings can significantly reduce conventional energy consumption in winter and summer. However, some problems arise in the utilization process, such as overheating, inconvenient operation control and low energy efficiency, etc. This work is a parametric analysis focusing on the automatic control and thermal efficiency improvement of the solar wall. An improved color-changing solar wall integrated with automatic control components, such as a photoelectric fan and temperature-controlled damper, was proposed in this paper. Based on the experimental data, the average daily heat output of the color-changing solar wall is 1.08 MJ per unit floor area on clear days in winter and the average thermal efficiency is 56.8%. Meanwhile, a quantitative analysis was carried out based on monitoring experiments for evaluating the thermal characteristic of automatic control components. Furthermore, in order to improve the thermal performance of the solar wall, parametric analysis was performed by numerical simulation. Results from this paper can provide a theoretical basis for the application of solar air collectors in modern buildings.

The Application of Innovation Mode in Building Engineering Management Based on Computer Technology

Buildings are one of the largest energy consumers in the world, and their energy consumption and greenhouse gas emissions account for one quarter to one third of the world’s total energy consumption. In addition, the building affects other areas far from its location, including river water, air quality and social traffic patterns. In China, more than 80% of new buildings are high energy consumption buildings every year, and more than 95% of existing buildings are high energy consumption buildings. At present, China’s energy consumption per unit floor area is more than 2-3 times that of developed countries. Through the corresponding computer technology application software, to create a simple building information model, architects in any stage of design, at any time, can easily evaluate the design scheme of the building, which is of great significance to the project management and construction of the building.

Preliminary Study on the GWP Benchmark of Office Buildings in Poland Using the LCA Approach

The decarbonisation goal stated in the Energy Performance of Buildings Directive (EPBD) regarding the building sector will be achieved only if the whole building life-cycle is considered. To fulfil this requirement, a benchmark based on the life cycle assessment (LCA) must be integrated into the early planning phase of buildings by designers. The estimation of such indicators requires the development of a database of building assessments. In this study, an LCA of 11 office buildings in Poland was used to set average values that can be used as a benchmark. The LCA methodology based on the Building Research Establishment Environmental Assessment Method (BREEAM) certification was used. The analysis did not concentrate on one type of office building. The main objective was to investigate a possible range of total Global Warming Potential (GWP) index values normalized to the usable unit floor area. The importance of the GWP of individual life-cycle phases was also considered. The study shows that the used methodology is adequate for LCA benchmark estimation to set preliminary average values for office buildings in Poland.

On mass quantities of gravity frames in building structures

This paper introduces a numerical study aimed at analysing and quantifying existing correlations between structural masses of the gravity frame in building structures (i.e. excluding lateral load resisting system) and some key basic design variables, such as bay areas of the frame layout, magnitude of floor loads and (main) structural material. Three material options are considered, namely: reinforced concrete, steel and engineered timber. A total of 31,380 different structural frame designs are parametrically generated and analysed to obtain a population of design data points that express the amounts of structural mass per unit of floor area. Least squares and quantile regression analyses have been utilised on the numerically generated sample population to evaluate any existing statistical trend between design variables and mass quantities. The set of regression coefficients so obtained is eventually organised into a tabular format, which allows for immediate estimations of the structural mass quantities (along with their uncertainty ranges) at an early stage of the structural design process. Such a table of coefficients represents the main finding of this work, as it can be straightforwardly combined with existing databases of embodied GHG and energy coefficients, therefore providing an effective estimation tool, for both practitioners and researchers, to quickly assess how both layout and load configurations affect the environmental impacts of their frame design.