Roel C.G.M. Loonen

• dr.
• Professor (Assistant) at Eindhoven University of Technology

The use of balconies in hot climates holds the potential to block direct solar radiation thus reducing energy consumption for cooling and enhancing visual comfort. However, balconies may also diminish daylight availability within the room, thereby affecting occupants’ satisfaction and wellbeing. This study aimed to provide balcony design recommenda...

Faults in photovoltaic (PV) systems are common during their operational lifetime. Existing PV fault detection methods, which are primarily designed for large-scale PV fields, struggle with distributed systems due to their reliance on on-site weather sensors and inability to handle complex local shading effects on PV performance in the built environ...

Balconies have the potential to promote airflow and regulate solar heat gain, which can reduce energy usage for cooling in buildings. However, designing these elements can be challenging due to complex trade-offs for natural ventilation and energy performance, highlighting the need for advanced simulation tools to guide balcony design decisions. Th...

Prefabricated temporary buildings are a promising solution for post-disaster scenarios for their modularity, sustainability and transportation advantages. However, their low thermal mass building envelope shows a fast response to heat flux excitations. This leads to the risk of not meeting the occupant comfort and HVAC energy-saving requirements. T...

This study investigated the representativeness of Test Reference Year (TRY) for the estimation of the performance of a system with photovoltaic (PV) modules and a battery energy storage system (BESS) in a high performance building. According to the technical standard EN ISO 15927-4:2005, the TRY is an artificial year made of 12 actual months select...

Thermal comfort models can be used to gain insight into important building design variables and predict whether a given design will provide satisfactory thermal conditions. There is a need for better industry standards and awareness towards thermal comfort as a multi-domain construct is increasing. However, despite the research efforts of academics...

Deep learning-based segmentation of urban digital surface models (DSMs) endures challenges from limited features, class imbalance, and sparse data, which limits the application of DSMs in urban solar energy assessment. In this study we propose a dynamic graph CNN (DGCNN) based segmentation model and address abovementioned problems by adding artific...

This paper proposes an innovative approach to analyse the energy behaviour of complex kinetic shading systems. Although several studies have analysed this topic, many are focused only on certain aspects or on simple shading systems due to a lack of tools for running reliable energy simulations on complex systems. This study aims to develop and vali...

Raytracing-based methods are widely used for quantifying irradiation on building surfaces. Urban 3D surface models are necessary input for raytracing simulations, which can be generated from open-source point cloud data with the help of surface reconstruction algorithms. In research and engineering practice, various algorithms are being used for th...

While the performance of PV systems and its associated uncertainties are well understood for standard test conditions in the laboratory, there is still limited knowledge about the magnitude and mechanism of the PV performance variability under actual operating conditions. This paper aims to identify the performance variability between identical roo...

Inverse problem approaches are relatively new and are growing in popularity in research in natural sciences and engineering. Inverse problem solving (or inverse design) comprises a rather heterogeneous collection of methods that are characterized by first setting the performance requirement(s) and then obtaining the optimal configuration of a mater...

Advanced fenestration systems (AFS) can respond to baseline functionalities and requirements in the remit of the transparent part of the building envelope (eg, reducing heat transfer, solar control and providing view out) and can combine these to a higher level of functionality aimed at providing an occupant with excellent indoor conditions while i...

High levels of non-dispatchable photo-voltaic (PV) generation integrated with the grid may disrupt its operation. Aligning the PV panels to follow local building demand can partially elevate this. We investigate the economic viability of alignment for buildings owners and grid utility. A bi-level optimization framework is built to determine the des...

This paper deals with the influence of assumptions regarding primary energy conversion factors in façade design optimisation studies, as a way of incorporating the effect of changes in the future electricity mix. A method for exploring the impact of these uncertainties using scenario analysis combined with weather data is presented. The method is a...

Accurate simulation of solar irradiance on facades and roofs in a built environment is a critical step for determining photovoltaic yield and solar gains of buildings, which in an urban setting are often affected by the surroundings. In this paper, a new modelling method is introduced that uses Digital Surface Model (DSM) point clouds as shading ge...

The present deployment of photovoltaic (PV) panels on the rooftop has been far below its potential. Stakeholders often see the PV as a strong design constraint, isolated from the built environment and not adapted to their requirements. Here, we propose a new design that combines the PV panels with a metal-organic framework based sorptive thermal ba...

Solar irradiance is a key input for modeling solar heat gains, daylighting and photovoltaic (PV) performance. However, solar irradiance is often affected by the surrounding urban environment, which is labour-intensive to take into account in building performance simulations. This paper introduces Pyrano, an open-source Python package for simulating...

Thermochromic (TC) materials can switch solar absorptance (α) based on temperature stimuli. When coatings with TC properties are applied on building envelope surfaces, the amount of solar heat gains can be controlled to reduce the heating and cooling demand of buildings. To date, limited research has been conducted in investigating optimal TC coati...

The aim of this paper is to evaluate the potential of a novel multi-state sun-tracking vertical-blind (ST-VB) concept using building performance simulation (BPS). A multi-domain simulation toolchain was developed and verified to evaluate the interior vertical-blind concept. The toolchain is used to quantify whole-building performance effects of des...

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...

'Smart' windows which reversibly increase their reflectivity upon heating are attracting considerable attention as devices for maintaining comfortable indoor environmental conditions. In this work, twisted nematic semi‐interpenetrating liquid crystal networks which lose their order upon heating are sandwiched between reflective linear polarizers. T...

Advanced building envelopes (ABEs) are innovative integrated systems that aim to increase the sustainability of buildings by providing flexible and efficient energy management solutions while safeguarding healthy and comfortable indoor environments. These building envelopes operate at the cross-section of architecture, engineering and data science,...

Information about the orientation (i.e. tilt and azimuth angles) of PV modules is a fundamental input for PV performance studies. However, this type of metadata is difficult to obtain for distributed in-use PV systems, which considerably impedes monitoring and diagnostics of PV systems and power grid management. Recently proposed parameterization m...

Building energy codes rely on climate zoning to establish regional requirements and benchmarks for building performance. Nevertheless, there is neither an accepted methodology for this purpose nor a scientific agreement when considering variables that provide quantitative results. This paper explores the relationships between the environmental perf...

There is a need to move the building stock towards a more energy self-sustained and self-reliant one. In most countries, photovoltaic installations have great potential to make dwellings energy-autonomous. To do so, the PV installation has to be coupled with a battery system capable of providing energy for periods no solar resource. Considering how...

Mainstream design approaches for low-energy buildings make use of highly-insulated building envelopes. However, if façades are always blocking energy exchange, the climatic resources surrounding the built environment might remain untapped or issues like overheating could arise. By reducing energy demand or improving indoor comfort, adaptive opaque...

Finding the fit-for-purpose modeling complexity for Building Integrated Photovoltaic (BIPV) systems in the early stages of building design is challenging, because typically at this stage the BIPV system is not yet designed in detail, which limits the applicability of detailed simulation models. This work targets to aid determining in which cases si...

The interest in occupant interaction with building controls and automation systems is growing due to the wider availability of embedded sensing devices and automated or intelligent building components that can integrate building control strategies with occupant-centred data and lead to greater occupant satisfaction and reduction in energy consumpti...

This paper presents a comprehensive sensitivity analysis on daylighting, visual comfort, and energy consumption of automated venetian blinds for open-plan offices. This research is using an integrated thermal and lighting simulation model in Grasshopper. The purpose is to identify which factors significantly affect daylighting level, visual comfort...

A full-size (1 × 5 m²) luminescent solar concentrator (LSC) has been constructed and the edge electric outputs from the attached photovoltaic cells monitored for a period of slightly over one year in the solar noise barrier (SONOB) “living lab” outdoor environment. The results of the edge electric output measurements were compared to ray-tracing si...

The present document includes a state-of-the-art review of solar envelope systems that are already on the market or that can potentially reach that stage in a short-medium timeframe (Technology Readiness Level ≥ 4). The analysis focuses on the technological integration of such solutions in the envelope and building, but non-technical issues such as...

This study presents a method for supporting control strategy development and sensor selection for automated solar shading systems from a building physics perspective using building performance simulation (BPS) and gives recommendations for quality assurance in making modelling decisions. With the proposed method high performance sensor strategies (...

The Perez sky diffuse model has been validated in many locations, however, studies have shown that the precision of estimation can be improved through localization of the model coefficients. This paper studies the effect of tuning Perez irradiance coefficients based on local information for estimating the incident solar radiation on tilted surfaces...

During the design phase, it can be of great value to quantify the performance robustness of proposed building designs in order to arrive at buildings that deliver the desired performance over their lifespan. Design-support approaches that take performance robustness into account need to find appropriate ways of transforming the large number of unkn...

The Perez sky diffuse model has been validated in many locations, however, studies have shown that the precision of estimation can be improved through localization of the model coefficients. This paper studies the effect of tuning Perez irradiance coefficients based on local information for estimating the incident solar radiation on tilted surfaces...

Building performance simulation tools have the potential for aiding the decision-making process in early design stages of an architectural project. As traditional simulation tools are based on a static design and adaptive façades encompass an envisioned movement of construction elements, there is a lack of supporting tools and workflows that can co...

One of the promising use cases of building performance simulation (BPS) is its role as a virtual laboratory in research and development (R&D) projects that aim to bring innovative building components from initial idea towards market introduction. By facilitating what-if explorations and whole-building insights, BPS can create complementary value, a...

Parked vehicles have the tendency to overheat quickly. This can lead to a negative impact on the thermal comfort of the driver and its passengers, as well as intensive use of air conditioning systems, and thus fuel consumption of the vehicle or, in the case of electric mobility, a reduced cruising range. In the search for effective measures to miti...

Adaptive or Intelligent façades are those that can interact with users and dynamically vary their performance or properties (controlling thermal or solar energy, air flow and/or daylight) in response to changing external conditions and indoor demands. Consequently, adaptive façades could help to ensure occupant comfort, health, well-being and satis...

This report is a result of extensive discussions within Task 56 of the Solar Heating and Cooling Programme (SHC) of the International Energy Agency (IEA). Innovative solar envelope technologies face multiple barriers, which prevent some of these innovations from contributing significantly against climate change. This report presents the barriers th...

The increased application of PV in urban environments goes together with a growing awareness of the need to consider the influence of partial shading and reflected irradiance on PV performance. Most of the conventional PV simulation tools do not have the capabilities to account for the possible additional PV yield due to reflected sunlight. On the...

Monitored power output data of photovoltaic (PV) installations is increasingly used for purposes such as fault detection and performance studies of distributed PV systems. The value of such datasets can increase significantly when they are paired with information about local irradiance and shading conditions, especially in urban environments. Howev...

The aim of this study is to assess the performance of prototype PV façade elements of various PV technologies, colors and textures. Within this context, a prototype PV façade demonstrator was constructed and monitored at SolarBEAT, Eindhoven. This prototype demonstrator consists of 9 façade PV panels of c-Si and CIGS technologies with flat and text...

Solar Envelope systems, which represent the technological response for meeting aesthetic requirements and solar renewable energy exploitation on building façades, are gaining a rising attention. However, they are still rare on the market. IEA SHC Task 56 focuses on the critical analysis, simulation, laboratory tests and onsite monitoring of market...

During the last decades, a great number of innovative building envelope materials and façade components have been developed. The majority of these technologies promise significant improvements in energy efficiency and occupant's comfort, with products that are easily available in the market. However, it remains a challenge to assess the performance...

Advanced glazing systems with special spectral characteristics or light redirecting behavior are commonly applied to improve building energy efficiency and indoor comfort conditions. The angle-dependent optical properties of such advanced windows can be markedly different from those of ordinary glass. To achieve accurate building performance predic...

The extensive use of thermal insulation in low-energy dwellings makes them susceptible to heat trapping in warmer periods. Construction elements with dynamically adjustable thermal transmittance properties, so-called dynamic insulation systems, can be a promising solution for reducing this overheating problem, while simultaneously lowering the ener...

Currently, several research projects investigate Additive Manufacturing (AM) technology as a possible construction method for future buildings. AM methods have some advantages over other production processes, such as great freedom of form, shape complexity, scale, and material use. These characteristics are relevant for façade applications, which d...

Traditional façade characterisation metrics such as U-value and g-value are of limited value in the design process of buildings with adaptive façades. This issue is particularly important for adaptive façade components that have the capability of controlling thermal energy storage in the construction thermal mass. Building performance simulations c...

This article presents an overview of possibilities and points of attention for modelling the performance of dynamic CFS in building performance simulation software. Following a detailed analysis of the unique requirements that are associated with modelling of CFS, a comparative study of the capabilities in different software implementations is pres...

Adaptive façades are building envelopes that interact with users and vary their performance or properties (controlling thermal or solar energy, air flow and/or daylight) in response to changing external conditions and indoor needs. However, effective adaptive façade solutions that provide an optimal balance between user comfort, satisfaction and en...

The integration of smart glazing and adaptive façade in buildings can lead to large performance improvements and added functionality compared to conventional static building envelope systems. This is achieved not only by embedding automatic/controllable (smart/active) switchable materials into the building envelope, but also including intelligence...

Thermal mass is usually positively associated with energy efficiency and thermal comfort in buildings. However, the slow response of heavyweight constructions is not beneficial at all times, as these dynamic effects may actually also increase heating and cooling energy demand during intermittent operation or can cause unwanted discomfort. This stud...

Ultra-lightweight concrete (ULWC) was recently introduced as a novel building material that combines moderate thermal insulation properties with load-bearing capacity. Its intended use as monolithic building envelope brings new opportunities in building physics, by merging characteristics of both heavyweight and lightweight construction types. This...

Science foresight comprises a range of methods to analyze past, present and expected research trends, and uses this information to predict the future status of different fields of science and technology. With the ability to identify high-potential development directions, science foresight can be a useful tool to support the management and planning...

Spong3D is an adaptive 3D printed facade system that integrates multiple functions to optimize thermal performances according to the different environmental conditions throughout the year. The proposed system incorporates air cavities to provide thermal insulation and a movable liquid (water plus additives) to provide heat storage where and wheneve...

Nowadays, the application of BIPV systems is growing very fast and among this type of technology, application of BIPV façade systems is becoming more common. A main question in this field is how we can ensure the intended performance of such systems considering different involved parameters over the system's lifetime. To do so, we need to be able t...

Adaptive building envelope systems have the potential of reducing greenhouse gas emissions and improving the energy flexibility of buildings, while maintaining high levels of indoor environmental quality. The development of such innovative materials and technologies, as well as their real-world implementation, can be enhanced with the use of buildi...

This paper reports on the research-driven design process of an innovative thermal mass concept: Convective Concrete. The goal is to improve building energy efficiency and comfort levels by addressing some of the shortcomings of conventional building slabs with high thermal storage capacity. Such heavyweight constructions tend to have a slow respons...

The assessment of adaptive facades presents a challenge because there is no established evaluation strategy to systematically reach this goal and many of the available building energy standards and codes have limited applicability for such advanced facades system. This paper reviews current evaluation methods for assessing adaptive facades system t...

Adaptive facades provide opportunities for significant reductions in building energy use and CO2 emissions, while at the same time having a positive impact on the quality of the indoor environment. Many different types of adaptive façade concepts (materials, components and systems) have already been developed, and an increase in emerging, innovativ...

How do living organisms capture, convert, store and process energy, water and sunlight? How does nature cool down, heat up, provide shade, and control light? Adaptability, the ability of a system to act in response to variations in environmental conditions often plays a key role in this context. Unlike living organisms, buildings are typically conc...

Electrically switchable broadband infrared reflectors that are relatively transparent in the visible region have been fabricated using polymer stabilised cholesteric liquid crystals. The IR reflectors can change their reflection/transmission properties by applying a voltage in response to changes in environmental conditions. Simulations predict tha...

Can computer simulations be used to predict occupant satisfaction and stimulate the design of energy-efficient, healthy buildings? This is the central question of this paper. In everyday practice, simulations are mostly used for building energy analysis and for limiting the occurrence of discomfort. There are, however, also opportunities for a more...

The Valley of Death is known as a metaphor for the lack of resources and expertise that impedes new ideas in their transition from lab to market. This gap also hinders innovation and adoption of new technologies for improved energy efficiency in buildings. This paper presents why and how building simulation can help close this gap, and shows some e...

Numerous demonstration studies have identified a large potential for adaptive facades to improve the energy performance and indoor environmental quality of buildings. However, to enable widespread application of these concepts, there is a need for more research and development, leading to innovative materials and components, and better scalable sol...

Innovations in high-performance building envelope components are an essential step towards reaching the ambitious targets for a more sustainable built environment. Enhancing product development workflows can turn out to be an invaluable resource in this process. In this paper we illustrate how building performance simulation (BPS) can be used to su...

There has been a huge increase in the global demand of energy over the last few years. One of the main contributors to energy consumption in buildings, cars, greenhouses and indoor spaces is the cooling devices needed to maintain the indoor temperature at comfortable levels. To reduce the energy used by cooling devices, we need improved light contr...

Automatically-operated dynamic facades can play an important role in reducing building energy consumption while maintaining high levels of indoor environmental quality. Facade automation, however, has a controversial reputation due to concerns about increased risks for occupant distraction and discomfort. This paper explores and quantifies the infl...

Climate adaptive building shells (CABS) are receiving increasing attention because they can enable high-performance building design that combines low energy consumption with good indoor environmental quality (IEQ). Various studies have acknowledged the potential of CABS with seasonal adaptation, but thus far, there is no method available to quantif...