Staf Roels

Staf Roels
KU Leuven | ku leuven · Department of Civil Engineering

Doctor of Engineering

About

206
Publications
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4,547
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Publications

Publications (206)
Article
Full-text available
This paper proposes a B-splines integrated method combining in-situ data with grey-box modeling to estimate buildings' dynamic solar gain more efficiently than the conventional white-box model and much more precisely than the classic grey-box model. Solar gain, referring to the overall indoor energy gain supplied by solar radiation, plays a vital r...
Article
Full-text available
Over the last few years, the application of a hydrophobic agent on a masonry wall has become popular due to its ability to reduce the amount of rain water absorption without changing the facade’s appearance. While the hygric properties of such hydrophobised materials are often investigated, research towards its penetration depth into materials is l...
Article
Full-text available
Urban building energy modelling has an essential role in the estimation of energy demand at urban or neighbourhood scales. However, current modelling methods have limitations in reproducing realistic gross energy usage. Although it is theoretically possible to simulate all components of the heating system in detail, such an extensive approach signi...
Article
Full-text available
Internal insulation remains often the only option to thermally upgrade massive masonry. Unfortunately, internal insulation can significantly change the wall’s hygrothermal performance, resulting in a higher risk on frost damage, wood rot of embedded beam heads, etc. The application of hydrophobisation is often put forward as a potential measure to...
Conference Paper
Urban building energy modelling has an essential role in the estimation of energy demand at urban or neighbourhood scales. However, current modelling methods have limitations in reproducing realistic gross energy usage. Although it is theoretically possible to simulate all components of the heating system in detail, such an extensive approach signi...
Technical Report
Full-text available
Assembling the knowledge, tools, and skills to reliably determine the (Heat Transfer Coefficient) HTC of a dwelling was a main driver for Annex 71. However, research has been carried out in this area for several years. What has set this work apart was the idea of measurement of the HTC using cost effective data, such as smart meters and on-board de...
Technical Report
Full-text available
Building energy performance assessment based on in-situ measurements: Physical parameter identification. Annex 71. International Energy Agency. Energy in Building Communities Programme. August 2021 ISBN 9789075741094 https://bwk.kuleuven.be/bwf/projects/annex71/ In Subtask 3 ‘Physical Parameter Identification’ of the IEA EBC Annex 71 project we...
Article
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A correct design of a timbre frame wall's composition is vital to avoid moisture damage. Unfortunately, currently, no general guidelines exist to determine the most optimal wall composition in a specific context. To develop such general guidelines, a comprehensive study is required, taking into account the inherent uncertainty and variability of in...
Article
Performing a probabilistic assessment of a building component can easily become computationally inhibitive. To solve this issue, the hygrothermal model can be replaced by a metamodel, which mimics the original model with a strongly reduced calculation time. In this paper, convolutional neural networks are used to predict hygrothermal performance. B...
Article
In literature, kaolin clay is often put forward to create a perfect hydraulic contact across the interface of building materials. This paper studies, based on imbibition experiments, if kaolin clay truly nullifies a hydraulic interface resistance between materials. Thereto, a comparison is made between the water uptake by monolithic samples and by...
Article
Full-text available
Measuring moisture content in building materials is essential both for professional practice and for research. However, this is a very complex task, especially when long-term minor destructive measurements are desired. The time-domain reflectometry (TDR) technique is commonly used for soil moisture measurements, but its application in construction...
Article
Full-text available
In this paper, the proper orthogonal decomposition (POD) method and the discrete empirical interpolation method (DEIM) are combined to construct a reduced order model for a cost optimal simulation of heat and moisture transfer in building materials. The POD-DEIM performance is assessed via two applications: a relatively simple case study on nonline...
Article
Full-text available
To lessen the computational expense of building energy simulations, the potential of model order reduction methods for assessing building envelope thermal performance is assessed, through both deterministic and probabilistic case studies of modelling heat transfer through a massive masonry wall. More specifically, two model order reduction methods...
Technical Report
Full-text available
This report is one of five deliverables related to WP6 ‘Development and evaluation of guidelines and web-based preliminary assessment tool ‘. The prime objective of WP6 is to develop and to assess written and web-based guidelines and a web tool (including a feasibility study of possible input and output data) for renovation of historic buildings wi...
Article
Full-text available
Cavity walls consisting of an outer leaf, a cavity and an inner leaf are a widespread building enclosure configuration because of their good performance regarding rain tightness. To increase the drying potential, open head joints are typically provided in the brick outer leaf, creating cavity ventilation. Even though this cavity ventilation has a l...
Article
Over the years, several dedicated on-site measurement tests have been developed to assess the heat loss coefficient (HLC) of a building envelope. These tests, and their associated data analysis methods, take the single-zone heat balance as a starting point. This assumption is, however, challenged when the measurement data is no longer collected dur...
Article
Full-text available
Due to interface phenomena such as compaction pores, a mismatch of the pore structure, etc., moisture transfer in multi-layered building elements can deviate from the moisture transfer observed for the combination of the separate materials. Several studies on interface phenomena make use of kaolin clay to provide – as a reference – a perfect hydrau...
Article
Full-text available
Measuring moisture content in building materials is crucial for the correct diagnosis of buildings’ pathologies and for the efficiency evaluation of the treatment solution applied. There are several different techniques available to measure the moisture content in construction materials. However, perform long-term minor-destructive measurements is...
Article
Full-text available
In this paper, the discrete empirical interpolation method (DEIM) and the proper orthogonal decomposition (POD) method are combined to construct a reduced order model to lessen the computational expense of hygrothermal simulation. To investigate the performance of the POD-DEIM model, HAMSTAD benchmark 2 is selected as the illustrative case study. T...
Article
Full-text available
To meet the increasingly stringent energy efficiency requirements, the market share of timber frame houses is steadily growing across Europe. Timber frame walls in Belgium are typically combined with a brick veneer cladding, which has a high buffer capacity for wind driven rain and a relative low cavity ventilation rate. Consequently, moisture leve...
Article
Full-text available
Due to the increasingly stringent energy efficiency requirements, timber frame houses are becoming more and more popular across Europe. Depending on the circumstances, timber frame walls might be exposed to high relative humidity or condensation conditions, leading to a risk of fungal degradation. In order to assess the durability of a timber frame...
Article
Full-text available
When simulating the hygrothermal behaviour of a building component, many uncertainties are involved (e.g. exterior and interior climates, material properties, configuration geometry). In contrast to a deterministic assessment, a probabilistic analysis enables including these uncertainties, and thus allows a more reliable assessment of the hygrother...
Article
The past decade has seen the rapid development of sensor technologies. Monitoring data of the interior climate and energy consumption of in-use buildings, so-called on-board monitoring (OBM) data, offers the opportunity to identify as-built energy performance indicators, such as the heat loss coefficient (HLC) of the building envelope. To this end,...
Article
Full-text available
Performing numerous simulations of a building component, for example to assess its hygrothermal performance with consideration of multiple uncertain input parameters, can easily become computationally inhibitive. To solve this issue, the hygrothermal model can be replaced by a metamodel, a much simpler mathematical model which mimics the original m...
Conference Paper
Full-text available
Reliable knowledge on how frost deteriorates building materials is necessary when assessing the hygrothermal performances of building facades. Unfortunately, the current frost-thaw testing methods do not offer dependable knowledge, as they only test at very low temperatures and very high moisture contents, contrary to the spectrum of milder conditi...
Article
Full-text available
Recently, there has been an increasing interest in the development of an approach to characterize the as-built heat loss coefficient (HLC) of buildings based on a combination of on-board monitoring (OBM) and data-driven modeling. OBM is hereby defined as the monitoring of the energy consumption and interior climate of in-use buildings via non-intru...
Article
Full-text available
Current frost resistance tests rely on freeze-thaw cycling at very low frost temperatures and very high moisture contents, conditions that not readily reflect the spectrum of milder frost conditions met at actual exposure. This analysis performs freeze-thaw testing on four types of ceramic brick at frost temperatures from −2 °C to −20 °C and moistu...
Article
When simulating the hygrothermal behaviour of a building component, there are many inherently uncertain parameters. A probabilistic evaluation takes these uncertainties into account, allowing a more dependable assessment of the hygrothermal behaviour. However, this often necessitates many Monte Carlo simulations, which easily become computationally...
Article
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In this paper, the potential benefits of quasi-Monte Carlo (QMC) methods for uncertainty propagation are assessed via two applications: a numerical case study and a realistic and complex building physical case study. The sampling efficiency of four quasi-Monte Carlo sampling strategies — Optimized Latin hypercube, Sobol’ sequence, Niederreiter–Xing...
Article
This paper explores the concept of characterizing the as-built Heat Loss Coefficient (HLC) of buildings based on-board monitoring (OBM), via energy consumption and temperature sensors, and time series analysis. It is examined (1) how the coefficients of different Auto-Regressive with eXogenous inputs (ARX) models can be interpreted and (2) whether...
Article
Full-text available
In this paper, the use of proper orthogonal decomposition for simulating nonlinear heat, air and moisture transfer is investigated via two applications: HAMSTAD benchmarks 2 and 3. Moreover, the potential of the reduced models constructed by proper orthogonal decomposition for simulating new problems with longer simulation periods is assessed. To i...
Article
Full-text available
A novel test setup and procedure to measure the vapour diffusion resistance of building materials and components are presented. In this test setup, a vapour flux across the test sample is induced by cooling down one of the sample’s surfaces by a cooling plate. The cooling plate also acts as a vapour tight plane and hence condensation is created. Th...
Article
Full-text available
Increasing the energy efficiency of the existing building stock can be accomplished by adding thermal insulation to the building envelope. In case of historic buildings with massive walls, internal insulation is often the only feasible post-insulation technique. Drawback of internal insulation is the modified hygrothermal response of the wall, whic...
Article
Full-text available
This study explores the potential of a centrifuge experiment for hygric property determination. In this method, a core sample is placed in a tube which is spun at different rotational speeds to create a distribution of moisture contents and capillary pressures. This way, a simultaneous determination of the moisture retention curve and moisture perm...
Article
The risk free applicability of interior insulation in the presence of wooden beam ends is still a point of discussion. Two phenomena enlarge the risk on wood decay when interior insulation is applied: (1) a higher moisture load in the masonry due to a reduced drying potential and (2) a lower temperature in the masonry resulting in a higher risk on...
Conference Paper
Full-text available
In this paper, the potential of model order reduction for simulating building performance is assessed, via a case study of modelling heat transfer through a massive masonry wall. Two model order reduction techniques – proper orthogonal decomposition and proper generalized decomposition – are investigated and compared. Moreover, to illustrate the pe...
Technical Report
Full-text available
This report comprises laboratory tests of internally insulated wall samples with embedded joist end constructions of three typical constellations (Denmark, Belgium, Germany). These tests aim to derive general conclusions about the performance of different insulation systems in comparison with each other with a focus on the joist end behaviour. Furt...
Chapter
Several important technological and economic trends are shaping the research on non-destructive testing techniques. X-ray computed tomography is also a NDT product of these ongoing developments and has become a very important tool for doctors, material scientists, geologists, biologists, civil engineers, bio-engineers, dentists, quality engineers,...
Article
To accelerate the hygric characterisation of porous building materials, dynamic flow and storage measurements in combination with inverse parameter estimation show a lot of promise. Therein though, the processing and interpretation of the experimental output can be challenging. This paper demonstrates the applicability of two swarm-intelligence (SI...
Article
In this study, two typical timber frame walls with brick veneer cladding have been constructed at KU Leuven to investigate the hygrothermal response of these constructions in a moderate sea climate. Main topic of research is the contradictory criterion for the wind barrier when it comes to the risk on interstitial condensation for winter and summer...
Article
Full-text available
The thermal resistance of building components is typically seen as a stationary parameter, although in reality, the quantity is often time varying. Several phenomena can lie at the origin of this: some of them are bound to the heat conduction mechanisms in building materials and cannot be prevented from occurring, while others are induced by extern...
Article
Full-text available
Most building component simulation software simplify the interior boundary conditions; only the temperature and relative humidity can be assigned. However, when performing a probabilistic assessment of the hygrothermal risks, a wider range of realistic indoor boundary conditions can be desired, and more indoor climate parameters need to be implemen...
Article
Even small air paths around the insulation layer in cavity walls may result in a significant reduction of its thermal resistance. This topic of air flow patterns bypassing the insulation layer has been studied in detail from the ‘80s and ‘90s on and let to clear recommendations for building practice [1]. However, the question remains to which exten...
Article
The applicability of interior insulation when wooden beam ends are embedded in the wall is still a topic of debate, as interior insulation may imply an enlarged risk on wood decay. This paper shows the impact of convective moisture transport on the hygrothermal performance of the wooden beams. In a hot box-cold box experiment, a vapour open capilla...
Article
To speed up the hygric characterization of building materials dynamic measurements can be applied; the data-processing of their experimental output can however be challenging. This paper presents the applicability of a metaheuristic, in the current study the Grey Wolf Optimizer, for the estimation of the vapour transport properties based on a ficti...
Article
Full-text available
Worldwide, the building sector represents the largest energy using sector, and it is still expanding. To reduce energy use of buildings, policy makers are increasingly demanding with regard to energy efficiency of buildings. Despite best planning effort, in practice some of these demands are not met: studies reveal that a building’s energy performa...
Article
Full-text available
In this paper, the potential of quasi-Monte Carlo methods for uncertainty propagation is assessed, via a case study of heat loss through a massive masonry wall. Four quasi-Monte Carlo sampling strategies – Optimized Latin hypercube, Sobol sequence, Niederreiter-Xing sequence and Good Lattice sequence – are applied and compared. Moreover, in order t...
Article
Several studies have shown that the actual thermal performance of buildings after construction may deviate significantly from its performance anticipated at design stage. As a result, there is growing interest in on site testing as a means to assess real performance. The IEA EBC Annex 58-project ‘Reliable Building Energy Performance Characterisatio...
Article
Full-text available
A qualitative and durable built environment requires an effective moisture control strategy. Moisture related problems can have an impact on the health of inhabitants or even jeopardize the building's structural integrity. Knowledge of the hygrothermal response and the drying potential of the current building enclosures under environmental loads is...
Article
In this article, the results of the hygroscopic characterization of a building material called ‘picón’, consisting of cement mortar and pyroclastic deposits from volcanic eruptions, are presented. The material obtained is used for the manufacture of blocks used in the construction of buildings in the Canary Islands. Picón is a heterogeneous materia...
Article
In current energy requirements, the thermal performance of buildings is assessed with simplified energy models. A performance label is calculated based on thermal properties of the constituent components of the building envelope. These properties, however, do not include factors such as workmanship issues, or moisture or airflow influences which mi...
Article
Several experimental procedures have been established to determine the convective heat transfer coefficient, a frequently used parameter in many engineering disciplines. Almost all of these methodologies focus on point or spatially averaged values. Yet, in many studies the spatial profile of the local convective heat transfer is of importance. In t...
Article
In timber frame construction in Europe, air barrier systems are typically realised at the interior side of the building envelope. Yet, in some applications such as renovation projects, it can be easier to provide the air barrier layer at the exterior. An exterior air barrier system, typically board materials in which the joints are sealed with tape...
Article
Full-text available
Reliable in-situ thermal characterisation allows to study the actual thermal performance of building components rather than the theoretical performance calculated from thermal properties of the constituent material layers. The most generally accepted method for in-situ thermal characterisation is the average method as described in ISO 9869. However...
Article
This paper reviews previous research work on the effect of air movement on the heat transmission losses in light weight building components in general and pitched roofs in particular. Air movement in pitched roofs is typically a mixture of three phenomena: (1) in/exfiltration, (2) natural convection and (3) wind-washing. While the importance of air...
Article
The article at hand presents the results of an extensive field study in which the air change rate behind rainscreen claddings has been measured. In total eight different full-scale test walls have been tested. The main parameter variations are: 1) the cladding system (brick veneer and sidings), 2) orientation (South-West and North-East) and 3) area...