Search

This paper provides an analysis of challenges and available solutions for exterior insulated panels suitable for deep energy retrofits of existing building envelopes. The analysis covers a review of available technologies that provide flexible retrofit insulated panels suitable for multiple climates and building typologies. Moreover, the paper proposes a new design for insulated retrofit panels that account for the majority of identified technical risks including cost, architectural diversity, climate variations, structural concerns, moisture resilience, air sealing, and water sealing. Additionally, the proposed design can be easily installed with minimal disruption to the occupants. A series of parametric and optimization analyses is carried out to identify the optimal design specifications for insulated panels suitable for deep retrofits of existing US housing stocks. The analysis results show that the optimal design criteria for the insulated panels can reduce heating and cooling energy consumption by up to 80% and HVAC capacities by 70%. Moreover, the results indicate that these insulated panels are highly cost effective for retrofitting US housing units located in cold climates. [ABSTRACT FROM AUTHOR]

This paper presents a systematic analysis of energy savings and cost benefits associated with several options for integrating energy efficiency and renewable energy technologies. The primary goal of this study is to assess the cost-effectiveness of achieving optimal net-zero energy (NZE) designs for residential buildings in Australia. Specifically, the analysis combines a series of sensitivity analyses and multi-objective optimizations to account for a wide range of design strategies for detached homes in four cities representing different Australian climates. The results indicate that not only are NZE designs technically feasible for all the considered Australian cities, but they are also highly cost-effective. This cost-effectiveness is attributed to the lower installation costs of rooftop PV systems as well as the beneficial interactive effects of proven energy efficiency strategies. Indeed, it is found that the deployment costs of rooftop PV systems can be recovered in less than 4 years. Moreover, the addition of thermal insulation in walls and ceilings can reduce both HVAC capacities and annual energy end-use by up to 59%. Based on an optimization-based design, NZE homes in Australia can have lower construction costs and, ultimately, lower life cycle costs than dwellings built to meet current energy efficiency standards based primarily on stringent building envelope thermal performance. [ABSTRACT FROM AUTHOR]

This paper summarizes the results of a comprehensive analysis to investigate the performance of both thermal comfort-based and temperature-based controls for schools in harsh hot climates of Saudi Arabia. The analysis considers the impact of building envelope characteristics including thermal insulation level of exterior walls and air leakage rate on the ability of both control options to maintain indoor thermal comfort while minimizing cooling energy consumption. The analysis utilizes a calibrated energy model for an existing Saudi school with monitored energy consumption data. The analysis results indicated that the thermal comfort-based control is able to maintain the predicted percentage of dissatisfied (PPD) value at 5% throughout the year for any combination of the exterior wall's R -value and air infiltration rate unlike the case of the temperature-based controls that do not maintain acceptable indoor thermal comfort conditions. However, the thermal comfort-based controls consume more cooling energy than the temperature-based controls. The analysis also revealed that the difference between the annual cooling energy of the PMV-based control and the temperature-based controls increases almost linearly with the cooling degree days of the site where the school is located. The analysis results indicate that acceptable indoor thermal comfort levels can be achieved using temperature-based controls when optimal temperature set points are used. [ABSTRACT FROM AUTHOR]

Although the energy and cost benefits for retrofitting existing buildings are promising, several challenges remain for accurate measurement and verification (M&V) analysis to estimate these benefits. Due to the rapid development in advanced metering infrastructure (AMI), data-driven approaches are becoming more effective than deterministic methods in developing baseline energy models for existing buildings using historical energy consumption data. The literature review presented in this paper provides an extensive summary of data-driven approaches suitable for building energy consumption prediction needed for M&V applications. The presented literature review describes commonly used data-driven modeling approaches including linear regressions, decision trees, ensemble methods, support vector machine, deep learning, and kernel regressions. The advantages and limitations of each data-driven modeling approach and its variants are discussed, including their cited applications. Additionally, feature engineering methods used in building energy data-driven modeling are outlined and described based on reported case studies to outline commonly used building features as well as selection and processing techniques of the most relevant features. This review highlights the gap between the listed existing frameworks and recently reported case studies using data-driven models. As a conclusion, this review demonstrates the need for a flexible M&V analysis framework to identify the best data-driven methods and their associated features depending on the building type and retrofit measures. [ABSTRACT FROM AUTHOR]

In this paper, a review of the adoption status of energy efficiency and renewable energy technologies is presented, specific to US residential buildings. Various technologies are reviewed and categorized as either their relative "higher adoption" or "lower adoption" rates within the US housing stock. More importantly, the review analysis investigates the main factors associated with their high or low adoption rates. Specifically, the paper provides a background of the historical progression of energy efficiency programs as well as sustainability certifications and standards for buildings. The review then analyzes specific building energy efficiency and renewable energy technologies applied to US residential buildings and their adoption rates. The review analysis indicates that building technologies are more frequently adopted for multiple reasons including requirements by codes and standards, incentives through green certifications, low implementation costs, and acceptance and popularity by the public. In contrast, technologies with low adoption rates have higher payback periods, are not required or highly incentivized through codes and certifications, have limited promotion about their benefits, or are not compatible with existing systems. By determining the reasons for the high and low adoption rates, mitigation options can be identified to increase the application of sustainable energy technologies in designing and retrofitting buildings. [ABSTRACT FROM AUTHOR]

The energy benefits of integrating PV panels with dynamic overhangs are evaluated for US residential buildings. Various control strategies are investigated to operate the dynamic overhangs to minimize annual net energy demands to account for both building energy needs and PV electricity generation yields. The analysis results indicate that dynamic overhangs can reduce significantly the annual energy demand for US residences compared to no-overhang and static overhang options even when controlled on a monthly basis and without any PV panels. Specifically, it is found that dynamic overhangs applied to southern facing windows for houses located in Golden, CO, can save up to 6% when no-PV array is installed and more than 35% when integrated with PV panels using monthly adjustments. Even higher savings up to 90% can be achieved for houses located in warm climates and those with larger windows. Moreover, PV-integrated dynamic overhangs can provide energy savings for windows oriented in any direction especially when adjusted on daily basis. • PV-integrated rotating overhangs are evaluated for US residential buildings. • Optimal control strategies are determined for the dynamic PV-integrated overhangs. • The dynamic overhangs can reduce the annual energy demand up to 90% for US homes. [ABSTRACT FROM AUTHOR]

To meet the increasing energy demand and to shave the peak, the Kingdom of Saudi Arabia (KSA) is currently planning to invest more on renewable energy (RE) seeking diversity of energy resources. Through the integration of demand-side management measures and renewable energy distributed generation (DG) systems, the study outlined in this paper aims at investigating the potential of hybrid renewable energy systems in supplying energy demands for residential communities in an oil-rich country. The residential community considered in this study, located in the eastern region of KSA, has an annual electrical usage of 1174 GWh and an electrical peak load of 335 MW that are met solely by the grid. The results of the analyses indicated that the implementation of cost-effective energy efficiency measures (EEMs) reduced the electricity usage by 38% and peak demand by 51% as well as CO2 emissions by 38%. Although the analysis of the hybrid systems showed that purchasing electricity from the grid is the best option with a levelized cost of energy (LCOE) of $0.1/kWh based on the current renewable energy market and economic conditions of KSA, RE systems can be cost-effective to meet the loads of the residential communities under specific electricity prices and capital cost levels. [ABSTRACT FROM AUTHOR]

Due to the rapid development of Advanced Metering Infrastructure (AMI), data-driven approaches are becoming more effective and accurate for Measurement and Verification (M&V) baseline energy modeling of existing buildings using historical energy consumption data. This paper develops and applies a comprehensive analysis framework suitable for developing baseline data-driven models to estimate energy savings from building retrofits. The framework employs common data-driven modeling approaches for building energy prediction, necessary data processing tasks, and industry-used evaluation methods. The modeling approaches considered by the developed framework include linear regression, ensemble models, support vector regression, neural networks, and kernel regression. The developed framework is applied to two case studies with different sources of energy consumption data generated via a simulated office building model and actual measurements obtained from a publicly available dataset. The framework applications to data from 170 buildings with 1-year data result in energy use predictions with medians of Goodness-of-Fit (GOF) scores that are less than 25%. • A data-driven framework is proposed to automate baseline modeling for measurement and verification analysis. • The framework considers several data-driven modeling approaches and timestamp frequencies. • The framework is able to predict within 5.54%, the energy savings incurred by retrofitting an office building. [ABSTRACT FROM AUTHOR]

The paper provides a systematic evaluation of the optimal optical characteristics of smart windows to maximize their energy efficiency benefits when deployed for residential buildings. The evaluation accounts for a wide range of design specifications and operation conditions of housing units including building orientation, window sizes, and climatic zones. Using integrated analysis aimed to minimize energy use required to heat and cool housing units, the optimal design and control settings are determined for two types of smart windows including those that can switch between only clear and dark tint states and those that can transition to multiple intermediate tint levels. The results from a series of sensitivity analyses show that the required design optical specifications for the smart windows could depend on several variables including primarily climate characteristics and window features including size, orientation, and U-value. Significant energy savings can be achieved by smart windows relative to the code-compliant static fenestration systems ranging from 21% in cold climates to 5% in warm climates. These energy savings can be achieved using stepped controls to set the tint levels of the smart windows. Additional albeit slight savings can be obtained through gradual controls for those smart glazing that have the capabilities to transition to intermediate tint levels. • A new analysis approach is presented for selecting optical properties of smart glazing. • Optimal optical properties for smart glazing can be identified for any residential building. • Energy efficiency benefits of smart glazing are enhanced using optimal optical properties. • Over 20% energy use can be saved by smart glazing relative to code-compliant systems. [ABSTRACT FROM AUTHOR]

This paper proposes an analysis methodology that can be applied by governments and local administrations to evaluate energy retrofit programs that involve entire building categories. Through a simulation based approach, that combines detailed energy modelling and algorithmic optimization, the analysis methodology is aimed to assess the magnitude of achievable energy savings for various retrofit levels along a cost-optimal path towards achieving net zero energy operation conditions. The proposed approach allows to identify the most cost-effective energy efficiency measures (EEMs) for building retrofits and their required investment costs. The retrofit potential benefits of the Italian office buildings stock is used as a case study to illustrate the application of the proposed analysis methodology. The results of the evaluation analysis for the Italian office building stock indicated a potential primary energy savings of 54% (i.e., 8000 GWh), when retrofitted through optimal combinations of EEMs and rooftop integrated photovoltaics. The optimal set of EEMs showed strong dependency on building typology and climate. In general, the cost-optimal combinations of EEMs and rooftop PV systems did not allow to reach net-zero energy operation conditions for any Italian office building type and climatic zone. [ABSTRACT FROM AUTHOR]

In the United Arab Emirates (UAE), buildings consume almost 90% of the total electricity used in the country. This paper provides a comprehensive overview of recent trends in energy consumption in the building sector as well as current efforts in promoting energy efficiency within UAE. Moreover, the paper explores available opportunities to improve energy efficiency of the UAE building sector. In particular, the impacts of three levels of energy retrofits are quantified based on results from existing literature and an optimization-based bottom-up analysis for residential, commercial, and governmental buildings. The analysis indicates that any level of energy retrofit for the existing building stock can be effective in reducing energy consumption and peak power demand as well as in lowering carbon emissions for UAE. It is estimated that a basic energy retrofit program applied to existing UAE building stock could achieve savings of 7550 GWh/year in electricity consumption, 1400 MW in peak electricity demand and reduce carbon emissions by 4.5 million tons/year per year. The program would have an average payback period of less than six months for the UAE government and would generate almost 9000 job-years. [ABSTRACT FROM AUTHOR]

In recent years there has been a widespread adoption of high reflectance (cool) roofing materials in hot climates to reduce a building's cooling load and energy use. While a cool roof can reduce the building's cooling load during warm months, it may regrettably increase the heating load in cool months thus reducing their overall effectiveness. One potential solution to preserving high cooling load savings without accruing a large heating load penalty is to implement a switchable roof reflectance technology; allowing a low reflectance roof during the heating season and a high reflectance roof during the cooling season. This paper organizes and summarizes the literature on cool roofs and switchable roofing materials as a tool for energy savings in buildings. It presents a review of material properties and advancements, energy savings and penalties, current codes, additional benefits and limitations, and recommendations for future research. Finally, the paper summarizes comparative analysis results of the energy performance for both static and switchable cool roofs. [ABSTRACT FROM AUTHOR]

This paper explores the potential energy savings of using dynamic cool roofs (DCRs) with seasonally variable reflective surface for various building prototypes when compared to static cool roofs. The analysis conducted demonstrates that the additional energy savings from DCRs depend largely on the climate, insulation level, and reflectance of the roof, as well as but to a lesser extent on the building thermal mass. This study shows that older buildings, with low insulation levels, in colder climates are the best target for retrofit using DCRs. Specifically, the results show that when a variable reflective costing is applied to low insulation buildings, source energy savings can be achieved and range from 4.33 to 19.44 MJ/m 2 (i.e., 1.6–4.9%) for residential units and from 1.17 to 18.00 MJ/m 2 (i.e., 0.3–3.9%) for offices. Based on an economic analysis, it is found that the break-even cost for a variable reflectance coating system with a 22-year life span ranges from 0.80 to 4.84 $/m 2 for residential buildings, and from 0.86 to 4.92 $/m 2 for commercial buildings. [ABSTRACT FROM AUTHOR]

The paper evaluates the potential energy efficiency benefits for dynamic sliding exterior shades suitable for windows of both new and existing buildings. In particular, the analysis outlined in the paper summarizes the energy performance of dynamic sliding shades when applied to windows for apartment units located in various US climates. A series of sensitivity analyses is performed using a detailed whole-building simulation coupled with modeling techniques of dynamic envelope systems to determine the optimal positions for the dynamic sliding shades to minimize the annual demand for US housing units. Several operation strategies are evaluated using continuous and stepped settings of the positions for the dynamic sliding shades using monthly, daily, and hourly adjustment frequencies. The results of the analyses indicate that the dynamic shades have significant energy efficiency potential for all US climates and design conditions with annual savings in HVAC energy end-use of over 50% especially in hot and mild climates. The performance of the dynamic shades is even higher for large and single-pane windows indicating that these systems can serve as retrofit alternatives to window replacements. • New and low-cost dynamic and insulated shading systems are introduced. • Energy benefits of the dynamic shades are assessed for residential buildings. • Optimal controls for the dynamic shades are determined for US climates. • Dynamic shades achieve over 50% reduction in heating and cooling energy use. [ABSTRACT FROM AUTHOR]

In this paper, passive cooling strategies have been investigated to evaluate their effectiveness in reducing cooling thermal loads and air conditioning energy consumption for residential buildings in Kingdom of Saudi Arabia (KSA). Specifically, three passive cooling techniques have been evaluated including natural ventilation, downdraft evaporative cooling, and earth tube cooling. These passive cooling systems are applied to a prototypical KSA residential villa model with an improved building envelope. The analysis has been carried using detailed simulation tool for several cities representing different climate conditions throughout KSA. The impact of the passive cooling systems is evaluated on both energy consumption and electrical peak demand for residential villas with and without improved building envelope for five cities, representatives of various climate conditions in KSA. It is found that both natural ventilation and evaporative cooling provide a significant reduction in cooling energy use and electrical peak demand for the prototypical villa located in dry KSA climates such as that of Riyadh and Tabuk. Natural ventilation alone has reduced the cooling energy end-use by 22%, while the evaporative cooling system has resulted in 64% savings in cooling energy end-use. Moreover, the natural ventilation is found to have a high potential in all KSA climates, while evaporative cooling can be suitable only in hot and dry climates such as Riyadh and Tabuk. Finally, the analysis showed that natural ventilation provided the lowest electrical peak demand when applied into the improved envelope residential buildings in all five cities in KSA. [ABSTRACT FROM AUTHOR]

• Optimized designs for controlled environment agriculture (CEA) facilities are described. • The designs utilize life cycle cost analysis to achieve optimal energy performance. • Energy efficiency and renewable energy measures are part of optimized CEA designs. • Optimal savings of over 65% can be achieved compared to baseline CEA designs. The paper describes a systematic analysis approach to optimize the design of indoor farming facilities considering both energy efficiency and renewable energy systems. The design optimization is based on a life cycle cost (LCC) analysis to account for both capital and energy costs over the lifetime of the facilities. The analysis indicates that LCC-based optimal designs consistently reduce annual energy consumption of the indoor farming facilities compared to the baseline case reaching up to 65%. The most effective energy efficiency measures for indoor farming facilities include high performance heating and cooling systems as well as optimized operational controls. While the heating and cooling system depends on the climate, daylighting controls and temperature settings are found to be consistently suitable for optimized designs in all US locations. The optimization analysis indicates that net-zero energy (NZE) designs for indoor farming facilities, while technically feasible, are typically not cost-effective in most US climates. Only NZE facilities located in Sacramento, CA, can be achieved cost-effectively. [ABSTRACT FROM AUTHOR]

• The optimal energy benefits of switchable insulation systems (SIS) are evaluated for office buildings. • When combined with precooling, optimally operated SISs can provide significant energy and cost reductions. • Optimal and hybrid controls are developed to operate SIS-integrated roofs and precooling strategies. • Optimized controls for SIS and precooling can reduce by over 20% energy use and 30% peak demand. In this paper, optimized controls to enhance the energy efficiency and demand response benefits of roof-integrated switchable insulation system combined with precooling strategies are evaluated for office buildings. A wide range of optimal cost functions are investigated to evaluate the total building energy saving as well as electrical peak demand shedding and shifting potentials. The results indicate that roof-integrated switchable insulation systems provide modest reductions even when optimally controlled of up to 5% and 4% savings in total building's energy use and electrical peak demand during a peak day. However, when precooling strategies are integrated with roof switchable insulation systems, optimal controls can enhance the performance of office buildings by reducing total energy use by up to 19% and electrical peak demand by up to 34%. Moreover, the analysis presented in this study demonstrated that roof-integrated SIS combined with precooling strategies offer significant potential to shape the energy demand profiles for grid-interactive efficient building (GEB) applications when optimized controls are deployed. [ABSTRACT FROM AUTHOR]

In both the US and French building sectors, significant efforts have been undertaken to reduce the environmental impacts of new constructions notably their fossil energy consumption and related carbon emissions. This paper summarizes the results of a comparative evaluation of optimal design specifications for office buildings for selected locations in both US and France using life cycle cost analysis approach. First, an overview of both the US and French approaches for developing building energy efficiency standards and design of high performance buildings is outlined. Then, a general approach for design optimization of energy efficient office buildings is presented. Finally, selected results of the optimal analysis are discussed. In particular, it is found that optimizing life cycle costs (LCC) resulted on average in 30% in primary energy savings for office buildings located in the US and 40% savings in France. However, it is found that LCC-based optimal building designs do not meet the French energy efficiency RT 2012 standard. When accounting for typical operating conditions, photovoltaic (PV) panels are needed in order to comply with the RT 2012 required thresholds for the total primary energy consumption of the office buildings located in the French cities considered in the analysis. [ABSTRACT FROM AUTHOR]

• A new design approach is presented for selecting smart glazing for office buildings. • Optimal optical properties for smart glazing are determined for office spaces. • Impacts of daylighting are considered to identify optimal optical properties. • Optimal smart glazing can achieve over 40% annual energy savings for office spaces. In this paper, a systematic analysis is presented to determine optimal optical properties of smart glazing to minimize energy demand for perimeter office spaces. The optimization analysis considers the impacts of design and operation conditions of commercial buildings including size and orientation of windows as well as the climate characteristics of the buildings. In addition, daylighting benefits are included in the analysis of smart glazing that can transition between clear and dark states as well as intermediate tint levels. The optimization analysis results confirm that smart glazing can provide substantial energy efficiency for office buildings when coupled with daylighting controls especially for cold climates and large windows. However, the analysis indicates that specific set of optical properties for both clear and dark states are required to achieve optimal energy efficiency benefits for smart glazing when applied to office spaces. Indeed, the presented analysis allows the identification of the optimal optical properties for smart glazing depending on several influencing factors including primarily the climate as well as the window size and orientation. Moreover, the magnitude of the annual energy savings achieved by the smart glazing depends largely on the optical properties of the static glazing type used as a reference. Using code-compliant static glazing as a reference, the energy savings incurred by smart glazing range from 1.2% to 13.3% depending on daylighting controls and climatic conditions. [ABSTRACT FROM AUTHOR]

In this paper, the energy benefits of switchable insulation systems (SIS) are assessed when applied as shades for windows as well as dynamic insulation for exterior walls of residential buildings located in European countries including Belgium and Spain. A series of analyses is performed for detached houses and apartments representing common Belgian residential buildings to determine the energy performance of SIS when deployed to windows and exterior walls and operated using simplified rule-based controls. The analysis results indicate that SIS-integrated windows can achieve significant energy savings for both dwelling types in Belgium, including the elimination of any mechanical cooling and a reduction of up to 44% of heating energy end-use. Moreover, the results show that SIS can offer even more energy efficiency and thermal comfort benefits when deployed to both windows and exterior walls for residential buildings. These energy efficiency benefits are higher, especially for reducing heating needs, for the milder climates of Belgium and Spain. However, it should be noted that the energy performance of SIS could be affected substantially by windows' orientation and occupants' behavior. [ABSTRACT FROM AUTHOR]

This study evaluates the energy savings resulting from the remediation of coil and filter fouling in constant air volume HVAC systems in residential and small commercial buildings. A computer model was developed to simulate the behavior of buildings and their duct systems under various levels of fouling. The model was verified through laboratory and field testing. Parametric simulation and sensitivity analysis results suggest that although fouling can have an impact on both air conditioner and furnace energy use, for the levels of fouling found in the literature, energy savings will be negligible for residential buildings and negative for small commercial buildings. [ABSTRACT FROM PUBLISHER]

Abstract: This paper presents a simulation environment that can evaluate the benefits of using simultaneously building thermal capacitance and ice storage system to reduce total operating costs including energy and demand charges while maintaining adequate occupant comfort conditions within commercial buildings. The building thermal storage is controlled through pre-cooling strategies by setting space indoor air temperatures. The ice storage system is controlled by charging the ice tank and operating the chiller during low electrical charge periods and melting the ice during on-peak periods. Optimal controls for both building thermal storage and ice storage are developed to minimize energy charges, demand charges, or combined energy and demand charges. The results obtained from the simulation environment are validated using laboratory testing for an optimal controller. [Copyright &y& Elsevier]

Abstract: This paper presents the results of a series of parametric analysis to investigate the factors that affect the effectiveness of using simultaneously building thermal capacitance and ice storage system to reduce total operating costs (including energy and demand costs) while maintaining adequate occupant comfort conditions in buildings. The analysis is based on a validated model-based simulation environment and includes several parameters including the optimization cost function, base chiller size, and ice storage tank capacity, and weather conditions. It found that the combined use of building thermal mass and active thermal energy storage system can save up to 40% of the total energy costs when integrated optimal control are considered to operate commercial buildings. [Copyright &y& Elsevier]

The potential for natural ventilation in building design to reduce associated building cooling and fan energy consumption makes it an area of great interest. However, its increased use is dependent on the availability of accurate modeling tools to predict its impact on a given building design. Network airflow models have been developed to predict airflows within buildings and between indoor and outdoor, which usually require user-supplied thermal conditions in a space. Because of the dependency between airflow and space temperature in naturally ventilated buildings, network airflow models need to be incorporated into whole building energy simulation models. This study reviews existing network models that may be used for natural ventilation design and investigates the capability and accuracy of four prevalent network airflow models to simulate a wide range of natural ventilation scenarios, with varying combinations of geometry and natural ventilation driving forces. Comparison of predictions with measurements obtained from literature shows that the tools are generally able to predict natural ventilation rates within 35% except for the wind-driven single-sided ventilation case. The article indicates some significant needs for improvement of the network airflow model for natural ventilation applications. [ABSTRACT FROM AUTHOR]

Abstract: A new lighting and daylighting control strategy is modeled and evaluated against conventional lighting and daylighting controls. The new lighting and daylighting control strategy can be incorporated in an energy management and control system (EMCS) to operate and control lighting fixtures in any indoor space. The new daylighting control can also be modeled and integrated in detailed building energy simulation tools. Through a validation analysis, it was found that the new control strategy provides more energy savings than conventional daylighting controls. Moreover, the validation analysis has indicated that existing daylighting control simulation analysis tools could overestimate lighting energy savings associated with daylighting controls. Moreover, it was also found that if calculated solar and illuminance data are used instead of measured solar radiation data, the errors in predicting lighting energy use when daylighting controls are utilized can be significant. [ABSTRACT FROM AUTHOR]

Abstract: This paper refines and validates the predictions of a simplified analysis method for evaluating the potential of daylighting to save energy use associated with electrical lighting. Specifically, impacts on daylighting performance are investigated for several combinations of building geometry, window size, and glazing type for several US and international locations. The impact of both dimming and stepped daylighting controls and their settings are also investigated. Predictions from the simplified method are validated using measurements obtained from field-testing of a daylighting control system utilized to operate lighting fixture illuminating an office space. [Copyright &y& Elsevier]

In this paper, the application of smart glazing systems as shading devices is evaluated for US residential buildings. Specifically, static and dynamic overhangs are considered using smart glazing that can change their tint state to reduce the heating and cooling thermal loads for prototypical housing units in high-rise apartment buildings. The tint settings as well as the overhang tilt angles are specified on hourly, daily, and monthly basis depending on the window orientation and the time of the year to minimize the annual energy demand for the housing units. The performance of smart glazed overhang systems is compared to both static and dynamic shading devices made-up of conventional opaque materials. In addition, the impacts of various design and climatic conditions are considered to assess the energy performance of the smart glazed overhangs. The results of the analysis indicate that the annual energy consumption for existing housing units with conventional windows located in Boulder, CO, can be reduced by over 7% for static smart glazed overhangs and by over 22% for dynamic smart glazed overhangs. These savings are even higher with larger windows and wider differentials between optical properties between clear and dark states. The smart glazed overhangs allow the use of low-cost smart glazing as a retrofit measure for existing buildings. Moreover, the smart glazed overhangs allow the specification of large windows for new constructions with limited energy penalties. • The energy performance of smart glazed overhangs is investigated for housing units. • Optimal controls are used to maximize the energy efficiency of the smart shades. • Switching of smart shades can be optimized on hourly, daily, or monthly basis. • Smart shades reduce energy demand up to 22% compared to unshaded clear low-E glazing. [ABSTRACT FROM AUTHOR]

The analysis presented in this paper evaluates the impact of both short-term and long-term stay home living on the energy consumption of Saudi residential building stock. The analysis combines monitored data obtained for a sample of housing units as well as the results from a validated Saudi residential building stock model. In particular, a bottom-up building stock modeling analysis approach is used to estimate the energy impact of the 2020 stay home order imposed due to COVID-19 in most of Saudi Arabia's regions between March 15 and June 15, 2020. Moreover, the potential influences of long-term stay home patterns on the cost-benefits of energy retrofit programs are investigated targeting Saudi existing housing stocks. The analysis results indicate that when normalized to weather, the 2020 lockdown has resulted in a 16 % increase in electricity consumption compared to the 2019 level specific to the entire Saudi housing stock. Most of this increase is associated with the higher energy end-use of lighting, appliances, and air conditioning associated with increased occupancy levels during daytime hours. For a transition to long-term stay home living, the results of the analysis show that the energy consumption of the Saudi housing stock is estimated to increase by 13.5 % compared to the current occupancy pattern. Moreover, the analysis indicates that the cost-benefits for energy efficiency retrofits are enhanced with long-term stay home living. • Households on average increased their energy demand during the COVID lockdown period. • Lighting and appliances are the main contributors to the energy consumption increase. • Energy consumption would increase by 13.5 % due to a yearlong home living pattern. • Retrofitting lighting and appliances are cost-effective options to curb energy demand. • Retrofitting AC units has beneficial effects on demand regardless of the living style. [ABSTRACT FROM AUTHOR]

• The energy benefits of switchable insulation systems (SISs) are evaluated. • When combined with precooling, SISs can provide significant peak demand reduction. • Using simplified rules, SISs can reduce cooling and heating energy uses by up to 60%. • When combined with precooling, SISs can reduce both energy use and peak demand. The energy efficiency and demand response benefits of switchable insulation systems (SISs) are evaluated for commercial buildings based on a comprehensive simulation analysis. In particular, switchable insulation systems, operated using temperature-based controls, are combined with precooling strategies to maximize the benefits from passive thermal storage of commercial buildings. The performance of switchable insulation system-based precooling strategies has been evaluated considering a wide range of design and operational control parameters. The simulation results indicate that switchable insulation system can achieve significant savings in annual heating and cooling energy end-uses reaching up to 65% and 25%, respectively, when considering deploying roof-integrated switchable insulation system during weekends in addition to weekdays for the various investigated climates. Moreover, the analysis found that when combined with precooling, the energy efficiency benefits from switchable insulation system are decreased. However, switchable insulation system-based precooling results in significant savings in electrical peak demand. For instance, operating switchable insulation system with precooling results in 18% savings in electrical peak demand when the building is located in Denver, CO. It has been demonstrated that precooling and switchable insulation system can provide both energy efficiency and demand response benefits for commercial buildings located in the US and other countries with diverse climates. [ABSTRACT FROM AUTHOR]

In this paper, the energy performance of an integrated adaptive envelope system (AES) is evaluated when applied to detached houses in four US climates. Three main technologies are part of the AES including cool roofs, movable PV-integrated shading devices (MPVISDs), and switchable insulation systems (SISs). For this study, the AES is operated to minimize annual heating and cooling energy uses. The analysis results clearly indicate that the integrated AES have high potential for cooling energy savings for residential buildings. Specifically, MPVISDs offer the highest contribution followed by attic and walls integrated SISs. Overall, the integrated AES allows on-site electricity generation and offers savings between 234 kWh/yr and 949 kWh/yr in cooling energy depending on the US climate. The deployment of AES alone allows US homes to almost reach net-zero energy designs especially in mild and hot climates. • A novel integrated adaptive envelope system (AES) is evaluated for US homes. • AES provides both energy efficiency and on-site electricity generation benefits. • AES can save up to 33% in annual cooling energy use for US homes. • The deployment of AES alone can achieve net-zero energy status for most US homes. [ABSTRACT FROM AUTHOR]

• A novel sliding/rotating overhangs is presented and evaluated for US residential buildings. • Both energy efficiency and environmental impacts of the dynamic overhangs are evaluated. • PV-integrated control strategies are considered to operate the dynamic overhangs. • The PV-integrated dynamic overhangs can result in net-zero building designs. The paper evaluates the benefits of integrating PV arrays with sliding and rotating overhangs to both generate electricity and reduce heating and cooling thermal loads for housing units in US apartment buildings. Optimal controls to operate the sliding-rotating overhangs are considered to minimize annual net energy demands with and without the integrated PV arrays. A series of sensitivity analyses is performed to assess the impact of design and operating conditions on the energy performance as well as the environmental impacts of the sliding-rotating overhangs. The analysis results clearly indicate that when integrated with PV modules, sliding overhangs can significantly reduce the energy demand for US housing units especially when they are set at the optimal angles specific to the building location to maximize their electricity generation and solar shading effects. Specifically, it is found that sliding overhangs can not only reduce energy demand but also can achieve net-zero energy conditions for US apartment units with large windows and located in mild climates even when monthly adjustments are applied to operate the shading systems. For instance, 9.2% of the total energy use of an apartment housing unit located in Boulder, CO, can be reduced using the sliding-rotating overhang with no-PV. In San Francisco, CA, more than 100% of the apartment housing unit energy demand can be avoided using PV-integrated sliding-rotating overhangs. To minimize design and operation complexities, it is recommended to consider sliding-only overhangs set at the latitude of the location to reduce both heating and cooling demand as well as increase PV array output. For instance, it is found that sliding overhang set at the latitude angle can be sufficient to achieve net-zero status and even a carbon-neutral operation for an apartment housing unit located in San Francisco, CA, even when adjusted on a monthly basis. [ABSTRACT FROM AUTHOR]

Controlled Environment Agriculture (CEA) applications, such as vertical farms and plant factories, have the potential to shift food production to be close to urban centers helping meet demands of large populations as well as achieving global climate goals. Growing crops in controlled environments has proven to be feasible for several applications, however, most involve energy intensive processes. The review analysis presented in this paper seeks to overview current CEA practices as well as potential energy efficiency technologies that can enhance the sustainability and the profitability of the indoor farming industry. Specifically, the paper reviews various CEA techniques, optimal indoor growing environments, successful case studies, and recommended energy systems research. The review analysis indicates that changes to a facility's envelope, HVAC, lighting, and incorporation of distributed generation technology can reduce consumption of electricity up to 75% in several CEA case studies. Future research into controls, dehumidification, lighting, and crop variety are vital for a wider adoption of CEA applications. • Controlled environment agriculture or CEA can help in meeting the increasing global food needs. • This review evaluates the limited studies to enhance the energy performance of CEA facilities. • Research needs to design and operate energy efficient CEA facilities are discussed. [ABSTRACT FROM AUTHOR]

A novel dynamic overhang system is evaluated in this paper when applied to control solar heat gains through windows of US residential buildings. In particular, the energy performance of the dynamic overhangs is compared to static systems using various operation scenarios. The main objective for the control strategies evaluated in the analysis is to minimize annual heating and cooling energy consumption when dynamic instead of static overhangs are applied to US residential buildings. The operation of the dynamic overhangs is adjusted to account for the range of positions allowed as well as the setting frequencies. In particular, the dynamic overhangs can be set on hourly, daily, and monthly basis depending on the window orientation and the time of the year. The analysis has indicated that the performance of the dynamic overhangs depend on their design specifications as well as on the window glazing type. However, the energy saving potential for the dynamic overhangs compared to static devices depend largely on the window size and the climate with significant reduction in cooling energy use achieved in hot and mild US climatic zones. Indeed, the dynamic overhangs can save over 45% of the air conditioning needs for US homes with window-to-wall ratio of 30% located in Phoenix, AZ, and San Francisco, CA, when automatically operated on hourly basis. [ABSTRACT FROM AUTHOR]

• Several control strategies are developed for attic switchable insulation systems. • A systematic analysis is carried out to evaluate these controls for US homes. • Switchable insulation systems can save up to 88% of heating/cooling energy needs. This paper summarizes the main findings for evaluating the effectiveness of simplified and advanced control strategies to operate switchable insulation systems applied to the attic of US residential buildings. Specifically, the evaluation analysis is performed for five US representative climates to determine the performance of several control options for dynamic insulation systems to minimize the heating and cooling energy end-uses for US homes. The control strategies considered include scheduled settings, temperature-based rule sets, and optimal control schemes. The comparative analysis results clearly indicate that the switchable insulation systems even when only applied to attics have significant potentials in reducing the cooling energy use of US residential homes especially those located in mild climates. Even when operated with simplified controls such as time-scheduled controls and temperature-based rule-sets, dynamic insulations are capable of providing substantial energy savings. In particular, controls using rules based on mean air and sol-air temperatures result in cooling energy savings ranging from 8% to 43% for all US climates. When optimal controls are used to operate attic dynamic insulation systems, up to 40% additional savings in cooling energy can be achieved compared to the best simplified controls at least when the building is located in Golden, CO. [ABSTRACT FROM AUTHOR]

• The types and benefits of occupancy-based temperature controls for residential buildings are reviewed. • A systematic analysis approach is performed for a wide range of temperature controls specific to Saudi households. • Smart occupancy-controls can save on average 36% of annual energy consumption for a typical KSA household. The paper describes the potential energy efficiency and demand response benefits of occupancy-based temperature controls applicable to residential buildings for the Kingdom of Saudi Arabia (KSA). Specifically, various spatial and temporal temperature controls are evaluated to account for spatial and temporal occupancy patterns associated to typical living styles of Saudi households. The analysis results show that the benefits of occupancy-based temperature settings can be significant when at least two thermal zones controlled by different thermostats exist within the same housing unit. Specifically, occupancy-based thermostat settings can save up to 38.7% of total annual electricity consumption for a dwelling located in Riyadh. Moreover, when the indoor temperature settings are adjusted spatially, a reduction of up to 34.7% in peak demand can result for most KSA regions. Using a bottom-up analysis approach, it is found that when scaling up to the entire KSA housing stock, the adoption of smart thermostats has the potential to reduce annual electricity use by 48 TWh/year or over 30% of the national residential sector energy consumption. [ABSTRACT FROM AUTHOR]

The paper overviews the current energy demand trends in the building sector for the Arab region using reported historical energy consumption. Moreover, the paper describes the current energy efficiency policies and regulations for all the Arab countries specific to both residential and commercial buildings. Finally, the paper evaluates potential benefits for large-scale energy efficiency programs specific to new and existing building stocks within the Arab region using a bottom-up analysis approach. The analysis of the available energy consumption for all the Arab countries has shown that the Arab region presents a significant variation in energy consumption levels between its sub-regions and countries. Indeed, the Arab region includes oil-producing countries such as Saudi Arabia with the largest energy use per capita in the World with over 9000 kWh/person of electricity used annually in buildings. However, the same region has the least developed countries such as Sudan and Yemen with the lowest energy use per capita in the World with barely 100 kWh/person/year of electrical consumption. The review of the existing regulations has indicated that several Arab countries have not implemented any energy efficiency codes and standards for building envelope, lighting, heating and cooling equipment, and appliances. A cost-effectiveness analysis has indicated that the Arab region can incur significant benefits in upgrading the energy efficiency of its new and existing buildings especially its households. Specifically, the adoption and the enforcement of stringent energy efficiency codes for new residential and commercial buildings can result in a reduction of 12.7 TWh/year in final annual energy consumption for the Arab region. Moreover, retrofit programs targeting existing buildings can save up to 470 TWh or a third of the building sector final energy consumption per year after 2030. Combining comprehensive energy efficiency requirements for new buildings and extensive retrofit programs for existing buildings would reduce the total final energy consumption of the building sector in the Arab region by 600 TWh by 2030 and by 900 TWh by 2050 if all the energy programs start to be implemented by 2020. [ABSTRACT FROM AUTHOR]

Abstract: Natural ventilation is a traditional cost-effective technique to cool and ventilate buildings. Proper simulation tools are highly desired to ensure acceptable thermal performance of naturally ventilated buildings and to assist the design and optimization of such buildings. This study is to advance the use of natural and hybrid ventilation concepts in building design by assessing the accuracy and usability of current thermal-ventilation models. Because of the similarity noted among various models and tools, a prevalent airflow-thermal modeling program, EnergyPlus, was evaluated by simulating three selected real buildings that were supplied with most detailed building and measurement information. The study of these cases reveals that the current model has (1) significant functional limitations for venting and exhaust fan control schemes; (2) need for additional relationships to describe horizontal openings and fully-open connections between zones; and (3) possible over-prediction of buoyancy-driven flows in the case of multi-story buildings. The study further indicates the building and measurement data that are critical for a more accurate validation of thermal-ventilation models, including, on-site measured temperature, wind, and solar conditions; measured volume flow rate data, at critical points throughout the building; and effective area and discharge coefficients for specific vents used in building. [Copyright &y& Elsevier]

Abstract: This paper provides a simplified analysis method to estimate the impact of building shape on energy efficiency of office buildings in Kuwait. The method is based on results obtained from a comprehensive whole building energy simulation analysis. The analysis takes into account several building shapes and forms including rectangular, L-shape, U-shape, and H-shape as well as building aspect ratios, window-to-wall ratios, and glazing types. The simplified method is suitable for architects during preliminary design phase to assess the impact of shape on the energy efficiency of office buildings. [Copyright &y& Elsevier]

This paper summarizes the results of a simulation analysis to determine the effectiveness of daylighting in reducing electrical energy consumption for office buildings in Egypt. Specifically, the impact on daylighting performance is investigated of window size, building size, daylighting control, and glazing type for three geographical locations in Egypt. It was determined that a window to wall area ratio of 0.20 minimizes the total annual electricity use for office buildings in three Egyptian locations, Cairo, Alexandria, and Aswan. A simplified analysis method is developed based on the analysis results to estimate the annual electrical energy savings attributed to daylighting. [ABSTRACT FROM AUTHOR]