Low-rise Office Buildings Research Articles

Eccentric compression behavior of L-shaped column fabricated by thin-walled square steel tubes based on self-drilling screw connections

In this study, a new L-shaped column fabricated by thin-walled square steel tubes (LFTST columns) based on self-drilling screw connections is proposed. The LFTST columns consisted of square steel tubes, U-shaped parts, angle parts, gusset plates, and self-drilling screw connections. LFTST columns possess several advantages including easy transportation, rapid assembly, and eco-friendliness. Consequently, they are suitable for low-rise buildings, such as village-building, low-rise dormitories, and low-rise office buildings. However, the compression behavior of LFTST columns remains silent. Five full-scale LFTST column specimens were subjected to eccentric compression tests. The variables under consideration included eccentricity (with values of 0 mm, 40 mm, and 80 mm), thickness (2 mm and 4 mm), and the number of gusset plates (0, 1, and 3). The failure modes, bearing capacity, load–displacement response, and strain development of the LFTST specimens were obtained. Subsequently, finite element (FE) models of LFTST columns were established and used to analyze the eccentric compression behavior of LFTST columns. The FE modeling results agreed well with the experimental results. A detailed parameter analysis was conducted to evaluate the effects of various factors. These factors included the thickness of the plates (2 mm, 3 mm, and 4 mm), the width of the gusset plates (100 mm, 150 mm, and 200 mm), limb spacing values (0 mm, 150 mm, and 300 mm), and eccentricity (0 mm, 20 mm, 40 mm, 60 mm, and 80 mm). In addition, the calculation formula for estimating the ultimate bearing capacity of the LFTST columns was derived employing the double coefficient product method. The proposed formula was validated by experimental and FE results.

Achieving net negative sensible heat release from buildings

Heat is added to the surroundings as a result of replacing natural landscapes with buildings. This includes waste heat from air conditioning systems and heat transferred into the environment from exterior surfaces. Here, we propose a new concept of “negative sensible heat release” from buildings—that is, buildings that put less sensible heat into the environment than that released from the unbuilt terrain upon which the building was constructed. We explore the potential for net negative sensible heat releasing buildings through simulation studies in hot arid and humid cities—Phoenix, and Houston. Results show that it is possible to achieve net negative sensible heat release from low-rise office buildings by simply increasing roof and wall solar reflectance using existing technologies. While typical 2-story office buildings can generate average heat fluxes of around 100 W/m2 (based on building footprint area), by increasing solar reflectance of the roof from 0.2 to 0.9 and solar reflectance of the walls from 0.2 to 0.65, the same building can generate net negative sensible heating of 20 to 40 W/m2. Increasing building insulation and energy efficiency of appliances and air conditioning equipment can further reduce the heat release from buildings. This points to a compelling mechanism whereby buildings can be designed or retrofitted to have a beneficial impact on the local thermal environment.

Driven pile foundation reuse in East London, UK

Multiple phases of redevelopment of the London Docklands, UK, have resulted in the need to replace existing structures with new, often larger, structures. This paper presents the case history of a 1980s low-rise office building (three to four storeys) being replaced by a medium-rise (five storeys + roof terrace) recreational building structure. The 1980s building was founded on driven closed-ended steel tube piles located within one of London’s historic docks. Subsequent to the 1980s building construction, London Underground (LU) tunnels were constructed below the dock in the late 1990s in close proximity to the structure. Piling in the dock adjacent to the LU tunnels resulted in restrictions to pile construction methodology. The new structure reused the driven piles in the dock and added new onshore bored piles to accommodate a larger building footprint landwards. The pile reuse justification used the original preliminary pile load test and driving records along with current design codes. The 1980s allowable working loads stated on the design drawing were lower than that required to support the new building, thereby requiring reinterpretation of preliminary pile load test results. The pile reuse assessment justified an increase in pile working load from 1050 to 1760 kN.

Evaluation of the Impact of Input-Data Resolution on Building-Energy Simulation Accuracy and Computational Load—A Case Study of a Low-Rise Office Building

Building-energy consumption is the primary aim of urban energy consumption, which can aid in optimization of building operation and management techniques, creating sustainable building and built environments. However, modellers’ understanding of the relationship between building-energy modelling (BEM) accuracy and computational load is still qualitative and deprived of accurate quantitative study. Based on a bottom-up engineering methodology, this study aims to quantitatively explore the effects of building-model input data with different resolution accuracies on energy simulation results, including evaluation of computational load. According to the actual parameters of the case-study building, 108 models with varying input resolution levels were developed to estimate hourly energy usage and annual mean ambient temperature. The results demonstrated that with input parameters at low resolution levels, geometric parameters such as exterior windows, interior windows, and shading exhibited significantly lower computational loads, resulting in reduced errors in the final simulation performance, whereas the occupancy schedule, thermal zoning, and HVAC configuration parameters exhibited significant declines in simulation performance and accuracy. This study presents a methodology applicable to the majority of low-rise, rectangular office structures. Future work would concentrate on carrying out comparison tests for different building forms and types while gradually improving the automation of the process to enable use of the appropriate accuracy level in assessing the crucial issue of energy-modelling input.

On the energy impact of cool roofs in Australia

Urban overheating is a serious environmental issue with a significant impact on cooling loads, peak electricity demand, indoor air temperature, health, pollution, sustainability, and the economy. Cool roofs – which are characterised by high solar reflectance (ρ) or albedo and high thermal emissivity (ε) – are one of the most effective technologies to mitigate the urban overheating effect and its undesirable impacts. The existing literature on the energy impacts of cool roofs in various building types and climate zones is vast but fragmented and predominantly assessed the building-scale and urban-scale benefits separately. Here, we computed the energy conservation potential of cool roofs in 17 building archetypes with different occupation hours, internal heat gains, thermal insulation levels, and building heights under various Australian climates. This study presents a holistic approach to assessing the magnitude and spatial variation of the cooling load savings, the peak electricity demand reductions, and indoor air temperature reductions generated by the building-scale and combined building-scale and urban-scale implementation of cool roofs in all representative building types under various climate conditions in Australia. In Sydney, a city with a warm/mild temperate climate, cool roofs can reduce the cooling loads of a typical low-rise office building without roof insulation by 10.2–13.8 kWh/m2 (37.6–42.0 %) during the summer months of January and February. When cool roofs are implemented in both individual buildings and the whole urban area, the cooling load conservation potential for the same building increases to 14.9–17.4 kWh/m2 (50.3–63.7 %). The corresponding peak electricity demand and indoor air temperature reductions by the combined building-scale and urban-scale application of cool roofs are 53–70 % and 11.2–12.0 °C, respectively. The energy conservation potential of cool roofs can be noticeable even for high-rise buildings with a high level of thermal insulation. We estimated that the cooling conservation potential by combined building-scale and urban-scale application of cool roofs can range between 4.0 and 7.1 kWh/m2 (29.3–48.3 %) in a new high-rise residential building with high levels of thermal insulation to 18.5–24.5 kWh/m2 (23–29.6 %) in an existing low-rise shopping mall centre with low levels of thermal insulation in Sydney. Cool roofs lead to additional savings as the reduced temperature increases the energy efficiency of air conditioning systems, with cooling load savings between 0.6 and 3.7 kWh/m2 (3–11 %) for a typical low-rise office building without roof insulation in Sydney. Also, the heating load penalties induced by cool roofs are negligible compared to the cooling load savings in all building types and Australian cities/climate zones except for non-commercial buildings in the cold climate of Hobart. Policymakers can use the results of this study to obtain a deep knowledge of the expected performance of cool roofs when applied city-wide to mitigate urban overheating and counterbalance its adverse impacts on energy uses and indoor thermal comfort.

A parallel decomposition approach for building design optimization

Integrated building design can promote high-performance, energy-efficient, and sustainable building designs by holistically considering design variables of simulation models from different disciplines. However, the complexity of the design increases drastically with the increasing dimension of the design problem. In some cases, solving high-dimension problems is not technically feasible nor time-efficient. Parallel decomposition can solve this problem by dividing the original problem into several smaller subproblems to be solved separately. Variable grouping is the first step of parallel decomposition. In order to obtain global optimal solutions, the existing variable grouping criterion focuses on whether there is an interaction between variables. Since many variables in building simulation interact, the building design optimization problems could be inseparable using this criterion. This study proposes a new variable grouping criterion, which can achieve the global optimum and decompose variables with strong interactions. This proposed criterion is combined with the existing one and presented as a dual-criteria variable grouping method for parallel decomposition. Sensitivity analysis is used to assess the existing criterion, and interaction plots are used to evaluate the proposed criterion. To demonstrate the applicability and runtime efficiency of the proposed parallel decomposition, the approach is applied to solve the single-objective optimization problems of a benchmark function and a low-rise office building. The results show that the proposed approach finds the global optimal solutions and takes less computation time than optimization without decomposition. In this study, each subproblem is solved while the variables in other subproblems are set as default values. With the results of the reference case of a full factorial design, it is found that the subproblem might achieve local optimum depending on the default values of variables in the other subproblems. This potential issue can be overcome by optimizing the subproblem with the strongest main effect first and using the results for subsequent subproblems with decreasingly weaker main effects.

Coordinated energy-environmental-economic optimisation of building retrofits for optimal energy performance on a macro-scale: A life-cycle cost-based evaluation

Given that energy-efficiency policies focus on meso- or macro-scale interventions, it is imperative to establish a macro-scale evaluation approach for building retrofits to support policymaking in building energy conservation, management and sustainability. This study applies the generic idea of optimising the energy, economic and environmental outputs to propose a facile framework for evaluating the prospects of building retrofits on a macro-scale. Here, an extensive optimisation approach integratinglife cycle cost evaluation and an environmental assessment is formulated, involving coordinated on-site survey, modelling and data analytics. The model framework is corroborated by a case study analysis focused on identifying the optimal retrofit solution for low-rise office buildings in Shanghai. Simulation results show that modifications in occupancy regime, improvements in natural ventilation, heating and cooling systems, cool roofs insulation and installation of renewable energy systems (such as geothermal and solar/photovoltaics) are the basic retrofit measures for a macro-scale intervention to attain maximum life-cycle benefits. Individually, an estimated investment cost for each retrofit project varied within RMB 1 – 5 million with a payback period < 13 years, depending on the building characteristics. Overall, an investment estimated at RMB 1.7 billion (with a payback period of 6 years) is required to achieve ~ 80% energy reduction with a carbon dioxide savings of ~ 243 Gg-CO2/yr. In summary, this study provides a guidance framework for stakeholders to evaluate investments on retrofit projects, including existing and prospective ones.

A target-driven decision-making multi-layered approach for optimal building retrofits via agglomerative hierarchical clustering: A case study in China

The optimization of energy, environmental and economic (3E) outcomes is the principal approach to identifying retrofit solutions for a sustainable built environment. By applying this approach and defining a set energy performance target, this study proposes a makeshift decision framework that integrates a data mining procedure (agglomerative hierarchical clustering (AHC)) into the decision-making process to provide a simplified 3E assessment of building retrofits on a macro-scale. The framework comprises of three model layers: (1) a building stock aggregation model, (2) an individualistic 3E model that provides the sensitivity analysis for (3) a life cycle cost-environmental assessment model. The framework is demonstrated and validated with a case study aimed at achieving the set energy targets for low-rise office buildings (LOB) in Shanghai. The model defines 4 prototypical buildings for the existing LOB blocks, which are used for the individual evaluation of 12 commonly applied retrofit measures. Subsequently, a simplified LCC-environmental assessment was performed to evaluate the 3E prospects of 2048 possible retrofit combinations. The results uniquely identify retrofit solutions to attain the set energy performance targets and optimal building performance. Furthermore, the decision criteria for different investment scenarios are discussed. Overall, this study provides building investors an innovative framework for a facile and holistic assessment of a broader range of retrofit alternatives based on set performance targets.

Effect of roof and ceiling configuration on energy performance of a metamaterial-based cool roof for low-rise office building in China

Cool roofs with higher solar reflectance and emittance can effectively reduce building energy consumption. However, it is still limited to use at night on account of the development of roof materials during the past decades. The newly proposed metamaterial-based cool roof (MCR) greatly improves the possibility of the radiative cooling in the daytime. To study the influence of MCR on the energy consumption for the office building, a small single-floor office was adopted to analyse the cooling performance of MCR by using EnergyPlus. In this study, the optimization analysis was conducted based on the proposed dimensionless thermal resistance ( θRTR) and roof pitch (Δ). Then the annual electricity saving potential of the office building with MCR was evaluated in details based on the selected cities from all five climate zones in China. The results show that more annual electricity saving can be achieved under the optimized values of θR7 = 1.53 and Δ = 20°. Furthermore, more than 15.7% of annual cooling electricity saving can be achieved while the optimized θRTR and Δ are applied.

Glass Curtain Wall Technology and Sustainability in Commercial Buildings in Auckland, New Zealand

Glass curtain wall provides an attractive building envelope, but it is generally regarded as unsustainable because of the high energy needed to maintain thermal comfort. This research explores the advances in the technology of glass cladding and the complex issues associated with judging its sustainability. It assesses the technology and sustainability of glass curtain wall on a sample of thirty commercial buildings in Auckland, New Zealand. Field observations of the glass-clad buildings, coupled with surveys of the building occupants and of glass cladding professionals are used to investigate the cladding characteristics, operational performance, sustainability aspects and future trends. The majority of the sample buildings are low-rise office buildings. The occupants like the aesthetics and indoor environment quality of their glass-clad buildings. However, continuous heating, ventilation and air conditioning are needed in order to maintain thermal comfort within the buildings and this has high energy consumption. The increasing use of unitized systems with double glazing instead of stick-built systems with single glazing improves the sustainability of the cladding through less material wastage and better energy efficiency. Inclusion of photovoltaic modules in the curtain wall also improves energy efficiency but it is currently too expensive for use in New Zealand. Environmental sustainability is also improved when factors such as climate, the orientation of glazed façades, solar control, ventilation and the interior building layout are considered. Any assessment of glass curtain wall sustainability needs to consider the economic and social aspects as well as the environmental aspects such as energy use

Correlation between building characteristics and associated energy consumption: Prototyping low-rise office buildings in Shanghai

The enormous building energy consumption in Shanghai necessitates the identification of standard buildings to offer guidance for the adequate design of retrofitting strategies in order to promote a sustainable built and architectural environment. In this regard, this study develops a methodological approach to establish prototypical buildings using performance index system (PIS) founded on an on-site survey. Emphasis is focused on low-rise office buildings in Shanghai. A total of 10 office parks containing 136 single low-rise office buildings in Min Hang District were systemically selected for survey and data collection. The proposed PIS includes building orientation, number of floors, window/wall ratio, heat and cold source type, plan form, and construction year. Using cluster and correlation analysis, the surveyed buildings are classified based on the impact of each PIS on the annual building energy use intensity. Based on this approach, the most influencing indexes are construction year, the number of floors, window-wall ratio and building orientation. This result refines the surveyed building samples to four prototypical buildings as representative standards for low-rise office buildings. Subsequently, typical buildings representing each of the prototypical buildings were defined. The stipulated approach provides a systematic framework for building classification, characteristic-based evaluation of building energy performance and identification of key performance index for building retrofit purposes.

Low-rise Office Retrofit: Prerequisite for Sustainable and Green Buildings in Shanghai

Commercial buildings comprise of 25% office blocks, largest proportion in commercial sector with highest energy consumption in Shanghai. Nevertheless, the demand for office space is still rising, driven by state-owned enterprises. Unfortunately, these existing buildings are energy inefficient as they barely adapt to present varying climate conditions of the province. Owing to aggravated climate change and rising urbanization rate of Shanghai, attention should be directed towards upgrade of office buildings to meet set sustainable building standards. 3-dimensional spatial characterization using vector topographic mapping posits low-rise buildings account for more than 50% of total buildings in Shanghai. Hence, retrofitting existing low-rise office buildings will significantly contribute to building sustainability. Subsequently, a retrofit package guideline suitable for sporadic energy use mode in rapidly expanding cities like Shanghai should be established. This nascent study postulates an updated correlation between climate change and building energy consumption in Shanghai. Based on the postulation, it is recommended that the best energy conserving building retrofit package is that which can mitigate the impact of both societal factors (like urbanization rate) and climate change to building energy consumption. In general, this study defines a foundation framework for building researchers and decision-makers to effectively evaluate retrofit measures for existing buildings become sustainability in Shanghai.

ZNE codes: getting there with performance trade-offs

To achieve zero net energy (ZNE) building codes, this paper proposes a model for building code regulators to consider that refocuses requirements from the efficiency of specific measures to the overall building energy performance. Using California’s Building Energy Efficiency Standards (Title 24, Part 6) as an example, the proposal presents a framework that establishes code compliance on whole-building performance using either the performance approach (energy simulations) or a new “simplified performance trade-off” pathway that achieves equivalent performance levels. An example of a simplified performance approach has been developed with the intention of allowing simple buildings to determine compliance with the energy code by specifying only a few building and efficiency parameters, including renewable energy system capacity. Building on these results, detailed trade-offs for low-rise office buildings are presented that utilize a selection of specific efficiency parameters that collectively achieve targeted performance levels. All major building components (e.g., HVAC, lighting, and fenestration) are represented and the selection of a less efficient design option triggers a requirement for higher efficiency in other areas such that the desired energy performance is achieved. Finally, we present our recommendations for developing simplified performance trade-offs for a larger set of building types and how our results could inform future code development activities.

The Application of Rainwater as Architectural Design Elements For Green Technology Solution In Low Rise Office Building

Performance of workers in terms of productivity level is determined by many related factors including a comfortable work space. Nevertheless, the discussion on the condition of work space environment namely in low rise office buildings and its related issues on thermal comfort in Malaysia are fairly new and is not well addressed. Past studies indicate that low rise offices found in many well-developed countries tend to utilize air conditioning as easiest ways to create a comfortable work space and to cool down the building interior. This factor had indirectly contributed to the increment of energy consumption namely in urban areas due to the rise of air condition consumption from 40% to 60% annually. As a result, contributed to the formation of urban heat island (UHI) which affect community’s environment and quality of life involving health and comfort. The objective of this paper therefore is to discuss and propose approaches on how to apply rainwater elements in architectural design for achieving thermal benefits through passive cooling. This is vital as Malaysia receives large amount of rainfall throughout the year in which this nature resources may provide advantages as sustainable source in cooling down the building temperature. For this purpose, case study as research strategy is adopted using mixed methodology combining qualitative and quantitative method. To conduct the data analysis, ECOTECT simulation and small field experiments are performed to investigate the cooling effect in low rise office building. Findings indicate that low rise office building which integrates rainwater elements in architectural design potentially improve the building thermal performance thus reducing building’s energy demand for space conditioning. This study is important as by adopting appropriate methods in addressing ecology issues will not only provide a comfortable living environment to the users but also established referential guideline in low rise office design.

Natural ventilation potential of the Mediterranean coastal region of Catalonia

Most of the Catalonian population and urban areas are located along the Mediterranean coastal zone and for this analysis three largest Catalonia's cities are chosen: Barcelona, Terrassa and Tarragona. Each city is a geographical representative of a different climate type according to the re-analysed Köppen–Geiger climate classification. The objective of this research is to demonstrate the effects of regional climate variations on the potential of natural ventilation (NV) application in building design. The first part of the article presents the availability of NV corresponding to yearly climate conditions applying the methodology “Climate potential for natural ventilation” (CPNV). In the continuation, the second analysis is calculated with building energy simulation software and displays possible refrigeration energy savings in three geographical locations. Mixed-mode (or hybrid-mode) and night-ventilation techniques are applied for the cooling process of a hypothetical low-rise office building model.

A-57 低層事務所建築における通風の利用に関する実験的研究 : その1 換気量の実測による流量係数の検討

A-57 低層事務所建築における通風の利用に関する実験的研究 : その1 換気量の実測による流量係数の検討

Assessment of users' responses to air change rates in free running office buildings

Often, building assessments do not account for users' social concerns in relation to buildings' physical characteristics. This study, therefore, assessed the responses of free running office building users to the objective measurements of air change rates in the spaces they occupy. This was done with a view to define a suitable quantitative expression for the social concerns of the users in building assessments, as well as with a view to examine the relationships between the users' responses and the physical characteristics of free running buildings. Measurements were taken in eight low-rise office buildings regarding indoor/outdoor air parameters to capture the air change rates in the buildings. These were done in 50 different spaces within the buildings at different floor levels and different fenestration orientations. The air change rates were correlated along social and physical dimensions with the responses of the occupants captured through questionnaire. Some relationships were observed among the social characteristics of the users and their rating of air change rates in the spaces, but none were statistically significant. Linear regression analysis, however, shows that one of the buildings' physical characteristics has a strong relationship with the users' responses to air change rates.

Distribution of Building Nonstructural Components in Height Subjected to Cost of Damage for Low-Rise Office Buildings

Exceeded losses of nonstructural components from structural ones in most demolished buildings in previous earthquakes and its limitation on functionality of critical facilities and building serviceability after earthquakes should be got the point of view for accounting loss of building as a merit for building performance. This paper attempts to demonstrate the significant role of distribution pattern of building nonstructural components in height accounting for economic losses due to seismic excitation. To achieve this purpose a new modified distribution of nonstructural components in height is proposed for three typical steel moment frame models by office occupancy and comparative assessments between two competing distribution of nonstructural components are conducted. Dealing with discussions, it could be concluded that the economic losses could be reduced by more astutely situating building nonstructural components in height considering type of dominated demands in a specific story without requirement to any alternation in component's type or quantity.

Optimation of Electrical Energy Generation for Low Rise Office Building with Folding-BIPV Concept

AbstractBIPV is an architectural concept that related to energy contribution. The system has functions of producing electricity as well as building form giver. The effectivity of BIPV depends on solar radiation received. Meanwhile, the solar radiation received depends on numbers of solar receiving area and environmental shading. Environmental shading will decrease the effectivity of BIPV. But, integrated configuration of folding-BIPV is expected to create more numbers of solar receiving area. The integrated configuration of folding-BIPV will create optimum BIPV, both in electrical generation and building form giver. Experiment to low rise office building in tropical climate is done by giving folding treatment. The experiment also considers about environmental shading. Evaluation is done by analyzing and optimizing the numbers and uniformity of solar radiation received. Simulation with ARCHIPAK 5.1 is used as experimental research tool. The simulation is used to calculate annual radiation received (kWh/m2) from folding-BIPV configuration. Manual calculation is used to calculate total annual radiation received (kWh) and uniformity percentage. Gradient diagram is used to do the optimation. Result of this research is an optimation of electrical energy generation in low rise office building which use folding-BIPV concept.

Multi-objective optimization of building envelope design for life cycle environmental performance

The building envelope incorporates significant amount of construction materials and is a key determinant of the embodied energy and environmental impacts in buildings. It is also a mediator between indoor and outdoor environmental conditions and has significant impacts on operational energy use in many types of buildings.The present article utilizes a multi-objective optimization algorithm to explore optimum building envelope design with respect to energy use and life cycle contribution to the impacts on the environment in a low-rise office building in Seattle, Washington. Design inputs of interest include insulation material, window type, window frame material, wall thermal resistance, and south and north window-to-wall ratios (WWR). The simulation tool eQuest 3.65 is used to assess the operational energy use, while Life Cycle Assessment (LCA) methodology and Athena IE are used to estimate the environmental impacts. Also, a hybrid artificial neural network and genetic algorithm approach is used as the optimization technique. The environmental impact categories of interest within the LCA include: global warming, acidification, eutrophication, smog formation, and ozone depletion. The results reveal that the optimum design scenario incorporates fiberglass-framed triple-glazed window, about 60% south WWR, 10% north WWR, and R-17 insulation.