Shading Control Strategies Research Articles

A Multi-objective Optimization of Window and Light Shelf Design in Office Buildings to Improve Occupants’ Thermal and Visual Comfort

In office buildings, an efficient design of windows and using light shelves as a passive design strategy significantly influence the thermal and visual comfort of occupants while enhancing the productivity and health of users. This study proposes a multi-objective optimization for the optimal design of windows and light shelves in office buildings to improve occupants' comfort. Initially, a parametric model was developed using Grasshopper parametric software. Afterward, the Honeybee energy and daylight plugin was employed for simulating thermal and visual conditions, and finally, multi-objective optimization was conducted with the Octopus plugin. This plugin can determine the best solution as a compromise decision for maximizing occupants' comfort. In this paper, an office building in Tehran has been chosen as a case study. The decision variables are window-to-wall ratio (WWR), shading control strategy, viewpoint, the transmission of glass, light shelf length, and light shelf height. The objective functions of the study are the annual average Predicted Percentage of Dissatisfied (PPD) and the annual average Discomfort Glare Probability (DGP). According to the results, the proposed optimization model leads to an 18.5–70.1% and 9.3–57.1% reduction in DGP and PPD indexes, respectively. The study findings provide practical and useful instruction for architects to select optimal specifications of windows and light shelves to develop occupants' thermal and visual comfort in office buildings.

Deterministic and probabilistic occupant-centric control's impacts on the indoor environment in free-running households

PurposeOccupant behavior can lead to considerable uncertainties in thermal comfort and air quality within buildings. To tackle this challenge, the use of probabilistic controls to simulate occupant behavior has emerged as a potential solution. This study seeks to analyze the performance of free-running households by examining adaptive thermal comfort and CO2 concentration, both crucial variables in indoor air quality. The investigation of indoor environment dynamics caused by the occupants' behavior, especially after the COVID-19 pandemic, became increasingly important. Specifically, it investigates 13 distinct window and shading control strategies in courtyard houses to identify the factors that prompt occupants to interact with shading and windows and determine which control approach effectively minimizes the performance gap.Design/methodology/approachThis paper compares commonly used deterministic and probabilistic control functions and their effects on occupant comfort and indoor air quality in four zones surrounding a courtyard. The zones are differentiated by windows facing the courtyard. The study utilizes the energy management system (EMS) functionality of EnergyPlus within an algorithmic interface called Ladybug Tools. By modifying geometrical dimensions, orientation, window-to-wall ratio (WWR) and window operable fraction, a total of 465 cases are analyzed to identify effective control scenarios. According to the literature, these factors were selected because of their potential significant impact on occupants’ thermal comfort and indoor air quality, in addition to the natural ventilation flow rate. Additionally, the Random Forest algorithm is employed to estimate the individual impact of each control scenario on indoor thermal comfort and air quality metrics, including operative temperature and CO2 concentration.FindingsThe findings of the study confirmed that both deterministic and probabilistic window control algorithms were effective in reducing thermal discomfort hours, with reductions of 56.7 and 41.1%, respectively. Deterministic shading controls resulted in a reduction of 18.5%. Implementing the window control strategies led to a significant decrease of 87.8% in indoor CO2 concentration. The sensitivity analysis revealed that outdoor temperature exhibited the strongest positive correlation with indoor operative temperature while showing a negative correlation with indoor CO2 concentration. Furthermore, zone orientation and length were identified as the most influential design variables in achieving the desired performance outcomes.Research limitations/implicationsIt’s important to acknowledge the limitations of this study. Firstly, the potential impact of air circulation through the central zone was not considered. Secondly, the investigated control scenarios may have different impacts on air-conditioned buildings, especially when considering energy consumption. Thirdly, the study heavily relied on simulation tools and algorithms, which may limit its real-world applicability. The accuracy of the simulations depends on the quality of the input data and the assumptions made in the models. Fourthly, the case study is hypothetical in nature to be able to compare different control scenarios and their implications. Lastly, the comparative analysis was limited to a specific climate, which may restrict the generalizability of the findings in different climates.Originality/valueOccupant behavior represents a significant source of uncertainty, particularly during the early stages of design. This study aims to offer a comparative analysis of various deterministic and probabilistic control scenarios that are based on occupant behavior. The study evaluates the effectiveness and validity of these proposed control scenarios, providing valuable insights for design decision-making.

Optimization Control Strategy for Transition Season Blinds Balancing Daylighting, Thermal Discomfort, and Energy Efficiency

Natural lighting in office buildings is often affected by excessive solar heat gain and discomfort glare, and the transitional seasons are no exception. Therefore, addressing the issue of natural lighting in buildings has always been a challenge in developing shading control strategies. This study designed a model-based calculation method for shading blind control indicators. The method combines existing physical models for sky conditions, solar radiation, heat transfer, thermal comfort, glare, and illuminance calculations and incorporates modifications and additions. Additionally, an equivalent energy-saving model for shading was established. A shading blind control strategy balancing indoor light and the thermal environment with energy savings during transitional seasons was proposed. In transitional seasons, this method can eliminate 100% of glare, reduce discomfort illuminance duration by 81.3% and heat discomfort duration by 87.5% and save 81.3% of lighting energy consumption when air conditioning is used. By comparing the simulation results of an office building in Xi’an with the results obtained from this calculation method, the absolute error percentage was found to be 6.83%, verifying the reliability of the calculation method. Finally, the proposed control strategy was compared with common methods such as no blinds, end-angle control, and fixed-angle control to evaluate its performance in terms of daylighting, thermal comfort, and energy savings. The results showed that the control strategy proposed in this study has significant advantages with respect to various performance indicators.

Visual comfort and energy use reduction comparison for different shading and lighting control strategies in a small office building

Automated shading and lighting control systems can be used to control solar radiation and daylight entering the space and reduce the lighting requirement, providing both energy savings and better visual comfort for occupants. Past studies that have explored automated lighting and shading control strategies typically report energy savings and visual comfort improvements over their respective baselines. However, across different studies, the assumptions for baseline models differ, as many daylighting studies use an experimental setup to measure various daylighting-based metrics to evaluate the performance of their control strategies in a real building. For instance, these actual buildings usually have different room sizes (depth and width), different window locations (height, width, and WWR (with/without split windows), window orientation (simultaneous windows in two directions), glazing properties and climate zones of the building location. As these input variables affect the result of daylighting studies, comparing percent improvement in energy savings due to the implemented control strategies across different papers can be challenging. This research uses a common baseline to evaluate the differences between a broad diversity of existing lighting and shading control strategies. The author also proposes an Integrated Control Strategy (IGS), which accounts for variables such as occupancy, HVAC state, solar radiation entering the space, and time of day for control. This study uses a multi-step modeling process, including daylighting and energy simulations using RADIANCE and EnergyPlus, respectively, in a Ladybug and Honeybee plugin environment. The results are used to quantify the differences in the existing control strategies to a common baseline model. The results suggest that complex rule based shading and lighting strategies such as an IGS performs only slightly better (6–12 % decrease in view to the outside, no glare, 82–88% lighting energy savings and 7.5–14.5% total energy savings compared shades fully open) when compared to existing glare metric based control strategy (4.5–9.5 % decrease in view to the outside, no glare, 63–72% lighting energy savings and 7–13% total laod savings compared shades fully open. Thus, if the addition of sensors is needed to support complex shading and lighting controls strategies, these sensors may benefit from being used for multiple purposes in order to justify their use.

Development of dynamic shading control for daylight measures in green buildings towards overall energy efficiency of lighting and air-conditioning systems

The introduction of daylight can improve buildings’ energy efficiency and bring benefit to occupant satisfaction. However, the introduction of daylight may accompany with excessive heat. Properly counterbalancing the energy consumption of air conditioning and lighting systems owing to the entry of daylight is a critical control target of dynamic shading adjustment in cooling season. Most dynamic shading control strategies in use only consider one single system. Additionally, for advanced control mode like performance-based control, the predictive model usually only examines the instantaneous effect of energy performance to determine the shading adjustment state, unable to quantify the overall influence of shading adjustment state on building energy consumption. In order to address this issue, special consideration is given to calculating the cumulative contribution of heat gains to cooling load in this study. An overall energy-efficient shading control metric is proposed and used as basis to develop optimized dynamic shading control strategy. An application example demonstrates that the SGR-Optimal control strategy can further save energy by 21.8% ~ 38.8% when compared to the Rule-based control strategy, thus allowing a better exploration of the energy efficiency potential of daylight measure.

Near-optimal adaptive predictive control model study for roller shades in office spaces

As improved building energy efficiency becomes mandatory, dynamic shading systems are expected to reduce building energy demand because their control mechanisms are increasingly self-adaptable to changes in the environment. Various shading control strategies had been proposed and compared in existing literature, but their energy performance can be further improved with a more comprehensive consideration of environmental changes and indoor demand. This study develops and validates an adaptive predictive control (APC) model for roller shades that combines simulation-based optimization of shading control with machine learning. The model predicts the appropriate position of roller shades based on multiple environmental parameters, minimizing the building energy demand. EnergyPlus and Python provide continuous energy simulation and data processing. Using pre-simulated datasets, machine learning algorithms develop APC models. The study scenario is a typical office space in Guangzhou, China. Quantitative analysis of the simulation results elucidates the effectiveness of the method. The performance of the model was evaluated using historical meteorological data from 2020. The proposed control model was able to achieve nearly optimal energy efficiency, reducing energy demand by 38.3% while reaching annual Useful Daylight Illuminances of 72.9%.

Analysis of the impact of automatic shading control scenarios on occupant’s comfort and energy load

Building envelopes should be responsive to boundary conditions changing in short-time, daily, or seasonal patterns. To this end, adaptive facades provide the ability to react, or benefit from, outdoor fluctuations and dynamic indoor requirements. On the other hand, the parallel trend of developing new technologies to control their performance, make adaptive facades more applicable to counterbalance both user’s comfort and building energy load. This goal can be met using active control mechanisms, either manually or automatically. Automatic shading controls require indoor/outdoor signal inputs to operate a shading system. However, in the literature, there is no consent on the effectiveness of automatic shading control strategies and all of the studies were investigated within specific environmental conditions. Therefore, this paper aims to compare the most used control functions and their implications on user comfort and energy load in different climate zones. To this end, EnergyPlus was used as a simulation platform to employ Energy Management System (EMS) for linking sensors, actuators to the control logic of adaptive venetian blinds. Then, a brute-force method was performed through Ladybug-tools to conduct 15,390 iterations parametrically. Results showed that climatic conditions impact the shading control scenario significantly, and the optimum scenario was an open-loop algorithm based on direct solar radiation due to the earlier activation of blind closure to block solar radiation while increasing lighting load at the same time.

Simulation-aided development of automated solar shading control strategies using performance mapping and statistical classification

This paper presents a structured, generically applicable, method for using building performance simulation to aid the development of comfort-driven solar shading controls by mapping predicted occupant comfort conditions to sensor measurements. The method uses confusion matrices as a statistical classification approach to facilitate (i) selection of sensor deployment strategies that offer beneficial trade-offs considering multiple performance aspects and (ii) identification of control algorithms that optimise comfort conditions using non-ideal sensors. The support method requires relatively little effort from a developer, only a small number of simulations and fits well within the current practice of shading control development. The method is tested using a sun-tracking control strategy for indoor roller blinds as a case study, which demonstrates that the method can identify high-performance solutions. Finally, generally applicable features of the method are extrapolated from the case study, and alternative applications and the method’s limitations are discussed.

Evaluation of the effectiveness of a multi-sectional facade with Venetian blinds and roller shades with automated shading control strategies

Daylighting plays an important role in building design. To maintain visual comfort and provide outdoor views, designers can use multi-sectional facades to extend daylit areas by daylight-redirecting devices and minimize undesired sunlight by movable shading devices. Beyond using specially designed light-redirecting systems, a combination of common shading devices – roller shades and blinds – may be used to meet aesthetic and cost requirements. However, the evaluation and simulation of multi-sectional facades are challenging, especially when the modeling involves complex fenestration systems and automated control strategies. In this study, we evaluate the effectiveness of multi-sectional facades with a roller shade and blind combination. Two control strategies are designed for two different multi-sectional facades, with a workflow developed for the evaluation. This workflow applies Radiance’s three-phase method for each shading state to model movable shades. External scripts are adopted to describe control algorithms and to generate annual results and daylight metrics. The workflow facilitates simulations of daylighting conditions for spaces equipped with both movable shading devices and daylight-redirecting devices under any customized control algorithms. The results demonstrate that the combinations of roller shades, blinds, and proper control algorithms greatly increase daylight near a rear wall compared to cases with only controlled roller shades, and do not cause glare. The combination with fixed blinds and controlled roller shades at the top section and another controlled roller shade at the middle section works well for rear spaces with south-facing or west-facing facades in both Taipei and New York.

Multi-objective simulation-based optimization of controlled blind specifications to reduce energy consumption, and thermal and visual discomfort: Case studies in Iran

This paper aims to present a multi-objective simulation-based optimization of architectural specifications and control parameters of a smart shading blind. Using the proposed method, implementation of control strategies on the window shading device and simultaneous optimization leads to a significant reduction in building energy consumption, and occupants' thermal and visual discomfort. Simulations are carried out using EnergyPlus, objective functions and decision-making parameters are identified by jEPlus, and multi-objective optimization is done by jEPlus + EA through NSGA-II. Optimization of the controlled blind is implemented in a typical office room located on a middle floor of a building, and the results are evaluated for four window orientations in six different climatic regions of Iran according to Köppen-Geiger climate classification. The decision variables are shading control strategy and its set-points and shading location, dimensions, angle, and material. The annual total building energy consumption, the predicted percentage of dissatisfied (PPD) and the discomfort glare index (DGI) are also considered as three objective functions minimized simultaneously. The weighted sum method is used to select the final answer from Pareto solutions. According to the results, based on the climate and the window orientation, the proposed optimization method leads to 2.8–47.8% decrease in the annual total building energy consumption compared to the initial design simultaneously with 15.5–69.9%, and 8.5–56.3% reduction in DGI and PPD indexes, respectively. The results clearly show how appropriate selection of the shadings specifications and their control strategy parameters can significantly not only prevent energy losses but also provide better occupants’ thermal and visual comfort.

Daylighting performance of three-dimensional textiles

The pattern and permeability characteristics that compose three-dimensional (3D) textiles are important as a textile shading component to the architecture, engineering and construction (AEC) industry. Moreover, due to their complex geometry, 3D fabrics require a detailed modeling for correct evaluation of performance.This paper aims to present and investigate the optical properties of six 3D fabrics proposed as an alternative to traditional roller blind shading systems, which could guarantee high daylight availability and visual comfort.The light transmission distribution for the different samples has been characterized by carrying out angular visual transmittance measurements, using integrating sphere optical benches, and virtual modeling using Radiance's genBSDF tool. The Bidirectional Scattering Distribution Function (BSDF) calculated with Radiance shows a good fit with the optical angular measurements, which were used as a benchmark and to calibrate models. The performance of the 3D textiles, in terms of illuminance, daylight availability, and glare, was assessed considering two of the set of 3D textiles as alternative materials for a movable internal roller shade system in an open office. The innovative system was compared with a traditional single layer fabric roller blind under different shading control strategies, 3D fabrics demonstrate the potential of increasing Daylight Autonomy while providing better uniformity and better connection with the outdoors due to a higher openness factor. The shading effect created by the 3D geometry of the textile can increase the openness factor while restricting glare.

Addendum

This article refers to:Comfort and energy performance analysis of different glazing systems coupled with three shading control strategies

Comfort and energy performance analysis of different glazing systems coupled with three shading control strategies

Shading control strategies are often required to optimize the balance between solar gains, daylight availability, glare protection, and view to the outside. Automated shading operation, when properly designed, may avoid performance losses due to manual operation while maintaining indoor environmental comfort. In this work, the integrated performance of different glazing systems coupled with three control approaches for roller shades is presented for a typical office space. The first control is a standard open–closed operation based on a workplane illuminance range, while the other two are able to set intermediate shade positions according to the solar position to maximize daylighting. The third control addresses excessive daylight on the workplane by imposing a workplane illuminance threshold to reduce the risk of daylight discomfort glare. Daysim, based on Radiance and the daylight coefficient method, was used to calculate the annual illuminance profile over the workplane, and Evalglare was used to calculate glare indexes. EnergyPlus was used for thermal comfort and energy analysis. The results were processed through a MATLAB code for transferring required information from one tool to another. Moreover, to assess the global performance of the shading controls and fenestration configurations studied, visual and thermal comfort were evaluated through a set of metrics able to express both the availability (the fraction of time with acceptable comfort conditions at specific positions) and the spatial usability (the fraction of space simultaneously within comfort range at specific moments). The energy performance was also quantified in terms of primary energy demand for heating, cooling, and lighting. The results showed that it is possible to balance daylighting, thermal and visual comfort, and energy use. This can be achieved by simultaneously selecting shading controls that allow adequate daylight without causing glare, and glazing properties with good thermal performance that allow adequate daylight (high visible transmittance) but limit solar gains (lower solar transmittance or solar heat gain coefficient [SHGC]) for moderate and cooling-dominated climates.

Effects of louvers shading devices on visual comfort and energy demand of an office building. A case of study

Daylight contributes to indoor visual comfort, enhances user satisfaction and productivity, and explains partially that, in office buildings, the use of glass in the facades has increased in the last few years, even in places where solar gains through windows contribute largely to glare, thermal discomfort and, consequently, excessive energy consumption. This paper evaluates the energy demand and visual comfort of a real case office building placed in a Mediterranean city, with a high window wall ratio (WWR). South oriented facades receive such a high solar gain that cooling demand cannot be handled by the current HVAC system. As an environmental friendly solution, a shading control strategy based on vertical and horizontal louvers is proposed.

Shading control strategy to avoid visual discomfort by using a low-cost camera: A field study of two cases

Daylighting in offices creates a comfortable and healthy working environment for its users. However, maximizing the amount of daylight can cause visual hindrance. To improve the visual and thermal comfort for the users, designers implement shading systems, which control the transmitted solar and visual radiation. To ensure a comfortable indoor environment, designers need to choose an appropriate control strategy. Different control strategies exist, but the acceptance and satisfaction of the user regarding these strategies remains quite low. Therefore, we developed a control strategy that is based on the comfort requirements of the users. The control strategy aims at avoiding visual discomfort for the user, while optimizing for daylight availability and improving user satisfaction by providing the possibility to override the automated control of the shading system. This is the first study where a shading device is controlled by a controller system with a low-resolution camera. The controller system captures High Dynamic Range images and evaluates a visual comfort parameter, namely the ‘Daylight Glare Probability’. The system controls the actuator of the shading device based on the assessed level of comfort. This paper demonstrates two experimental case studies where the controller system and the control strategy are implemented. The controller system is able to keep the visual hindrance below a predefined limit, while sufficient daylight can still enter the office room.

A Comparison of Smart Shading Control Strategies for Better Building Energy Performance

A Comparison of Smart Shading Control Strategies for Better Building Energy Performance

Solar shading control strategy for office buildings in cold climate

The objective of the present study was to develop a solar shading control strategy for venetian blinds applied on office buildings in cold climates in order to achieve acceptable energy use and indoor environmental performance. A control strategy based on a combination of internal and external shading develop within the Norwegian R&D project “Fasader i glass som holder hva vi lover” (“Glazed facades keeping what we promise”, translation by author) was extended with factors related to glare, daylight sufficiency and view to the outside. The study used full-scale experiments in a test room in Aalborg, Denmark, to verify the performance of the control strategy, and the study was further expanded with annual simulations of the office room at different locations. Results of the annual performance illustrated that the proposed control strategy would lead to satisfying compromises between the energy and indoor environmental performance. Generally, the investigation exemplifies the importance of doing integrated evaluations of energy use and thermal and visual comfort when making decisions regarding solar shading control strategies.

Daylighting Design for Energy Saving in a Building Global Energy Simulation Context

A study on the impact that different daylighting solutions have on the global energy demand of a space is presented. The methodology relies on dynamic simulations carried out with Daysim and EnergyPlus used in synergy to perform a parametric study to assess the indoor daylighting conditions and the energy performance of rooms with different architectural features: room depth, window size, external obstruction angle and glazing visible transmittance. Furthermore, different lighting and shading control strategies were tested. The results of the study demonstrated that optimizing daylight can lead to a reduction of up to 30% in the global energy demand for a building.

Metal Mesh as Shading Devices and Thermal Response of an Office Building: Parametric Analysis

Windows are the most important part of the building façade to control solar gains, thermal losses and visual comfort. Office buildings usually have medium-high WWR (window to wall ratio value) and high internal gains (due to users, lighting and appliances). For this reason, they require a good balance between thermal and visible performances of transparent façades and shading control strategies to avoid overheating, optimizing daylighting aspects. A sensitivity analysis was assessed to evaluate primary energy use for heating, lighting and cooling for conventional Italian single office units equipped with static metal mesh shading devices with different geometries and openness factor values. Different location (Milan, Palermo), orientation (south and west) and WWR (33% and 100%) were analyzed. Hence shading devices alternatives as venetian blinds and sun control windows are proposed as a comparison.

Fener: A Radiance-based modelling approach to assess the thermal and daylighting performance of complex fenestration systems in office spaces

A new Radiance-based modelling approach called Fener is presented. The motivation is to be able to perform detailed analyses of complex fenestration systems (CFS) from the energetic and daylighting points of view in a computationally efficient manner, so the benefits of innovative products can be easily quantified. The model couples daylighting and thermal simulations in a time-step basis, so that shading control strategies that depend on thermal variables, such as indoor air temperature and energy load, can be simulated without iterating between full-year simulations of a thermal model and a daylighting model. Fener is a single-zone energy model that uses the three-phase method and bi-directional scattering distribution functions (BSDF) to predict the transmitted solar irradiance and indoor illuminance of office spaces with CFS. An evaluation of the model is presented. Fener is tested against EnergyPlus and classic Radiance for different fenestration systems and sky conditions. Cooling and heating energy demand, transmitted solar irradiance and indoor illuminance are compared. As an exemplary application, Fener is used to assess the performance of an innovative perforated lamella system together with a control strategy that depends on indoor air temperature.