Arnold Janssens

Ghent University | UGhent · Department of Architecture & Urban Planning

The subject of this paper is to analyse how the regulatory calculated energy use relates to the real total energy use for new or thoroughly renovated Flemish single-family houses where electricity is the only energy carrier. Additionally, the authors determine whether statistical data-driven models can help inform current and future home owners and...

Large-scale statistical studies on the gap between the real and regulatory energy use in residential buildings in Europe have shown that the regulatory calculation overestimated the real energy use, inflated true energy savings and undermined national energy policy making. Using data from 122,680 Flemish existing single-family houses, this research...

Twelve quasi-identical almshouses with an architectural-historic value were reno-vated, because of their high energy use, poor indoor comfort and numerous moisture problems. Aerogel plaster was applied for the hygrothermal upgrade of the uninsulated brick walls, while limiting the reduction of living space in these very small houses and keeping the...

The Energy Performance of Buildings (EPB) regulations aim to reduce primary energy use and carbon dioxide emissions of buildings, which are the result of creating a comfortable and healthy indoor environment. In this study, the influence of climate change on the regulatory EPB calculation results is analysed for the Flanders region in Belgium. The...

Recent studies indicated that window opening behaviour is related to environmental and contextual factors, as well as to practices of everyday life, such as morning routines and daily activities. To the authors’ knowledge no studies have been conducted that focus on the habitual window opening behaviour in residential buildings. The aim of this stu...

Reaching the European Union's 2030 targets for primary energy use (PE) and CO2 emissions (CE) requires an accurate assessment of how different technologies perform on these two fronts. To calculate the PE and CE associated with the consumption of electricity (e.g. by an electric vehicle or a heat pump) conversion factors (CFs) are required, namely...

Most of the window use models developed for building energy simulations include physical environmental variables as drivers. Even though it is a common approach to include these variables, the validity of this approach can be questioned based on observations in the literature regarding the consistency and seasonality of the relationship between the...

******* PUBLISHED VERSION: http://dx.doi.org/10.1016/j.rser.2021.111182 ******* Reaching the 2030 targets for the EU primary energy use (PE) and CO2eq emissions (CE) requires an accurate assessment of how different technologies perform on these two fronts. In this regard, the focus in academia is increasingly shifting from traditional technologies...

Many building components rely on pressure equalization to achieve a good performance in respect to watertightness. Guidelines on geometrical constraints derived from numerical models and experiments are widely spread, but it appears these are only valid for dry conditions. To evaluate the impact of rain on the pressure equalization in facades, a ge...

Often there is a significant difference between the actually measured and theoretically calculated energy use. The deviation between the two can be a result of errors in design, construction or commissioning, due to the technical performance of building components and installations that don’t meet the design requirements. But equally, incorrect ass...

The use of solar shading can have an important influence on the internal heat gains, especially in zero-energy buildings. However, the research in literature is almost uniquely focused on offices, while information on the use of solar shading in residential dwellings is lacking. Therefore, the solar shading behaviour of occupants of a nearly zero-e...

The watertightness of solid masonry walls is generally based on the concept of buffering and afterwards drying out the absorbed rainwater. In cavity walls, on the contrary, the air layer provides a capillary break between the inner and outer leafs allowing drainage of rainwater and preventing infiltration to the interior wall surface. For assessing...

Background: Legionnaires disease occurs worldwide. Many authorities have guidelines and regulations to prevent and control Legionella in water systems. These regulations are based on often very limited field and laboratory observations and measurements. They are, therefore, very different from country to country. This article aims to map the exist...

The energy needed for the production of domestic hot water (DHW) represents an important share in the total energy demand of well-insulated and airtight buildings. DHW is produced, stored and distributed above 60°C to kill Legionella pneumophila. This elevated temperature is not necessary for DHW applications and has a negative effect on the effici...

The performance assessment of ventilation systems often focusses only on CO 2 and humidity levels. The indoor Volatile Organic Compounds (VOC) emissions of building materials or other products is thereby overlooked. The new generation of ventilation systems, Demand Controlled Ventilation (DCV), are systems that do not supply the nominal airflow con...

The increasing application of smart and digital energy meters leads to an increasing availability of frequent -e.g. hourly- and long-term measurements of the actual energy use in occupied buildings. In the resulting energy use time series, the diurnal fluctuations in energy use are recognised and similarities between diurnal profiles for various da...

The occupants’ window opening behaviour can have a substantial influence on the indoor climate and the energy use in low energy dwellings. In literature, most window opening models are based on outdoor and/or indoor climate variables. However a study of Verbruggen et al. [1] revealed that these models are not able to predict the window opening beha...

RESUMEN Las Terrazas constituye un ejemplo singular de una comunidad rural dedicada a la explotación del turismo en Cuba. En la actualidad, se considera una experiencia rural de desarrollo sostenible por las acciones desarrolladas con relación a la conservación del medio ambiente, el desarrollo sociocultural y el aprovechamiento de los recursos nat...

In this research a VOC model for medium density fibreboard (MDF) incorporating the influence of temperature and humidity is derived from literature to replace the traditional method of using a constant emission model. Using this new VOC model in a CONTAM model, two ventilation systems for dwellings according to the Belgian standard and two demand c...

Residential building energy performance indicators are compared with a different approach for the normalization of the characteristic yearly primary energy use. The purpose is to analyse which approach results in a fair assessment of more compact, energy-efficient building geometries, and of smaller building size. A normalization by floor area is s...

The preservation of early Netherlandish panel paintings gets a lot of attention as they are an important part of the cultural heritage of the lower countries. Indoor humidity fluctuations are the main cause for mechanical damage of these artworks. To estimate the risk of mechanical damage, the intention of the authors is to model the moisture trans...

This paper gives an overview of the results of the European demonstration Project ECO-Life (2010-2016) in Belgium. The goal of the project was to transform a number of social housing neighbourhoods in Kortrijk, Belgium into a sustainable carbon neutral community. A neighbourhood of single family social houses built in the 1950’s was partly replaced...

Due to an uncontrolled indoor climate or a poorly designed climate system, the environmental conditions in historical buildings are often suboptimal for the preservation of works of art. This is also the case for Jan and Hubert Van Eyck's Ghent altarpiece, which is located in one of the chapels of the Saint Bavo Cathedral in Ghent, Belgium. Years o...

This paper studies the sensitivity of heat losses in collective heat distribution systems using a simplified calculation method. The approach is applied to a specific type of heat distribution system where the network distributes heat for both space heating and sanitary hot water. The proposed methodology takes design parameters influencing the the...

Since 2012 a quality control system is in operation in Belgium to provide confidence in the quality of the works of cavity wall insulation in existing walls. When the works are in line with the quality framework, the installer may provide a declaration of conformity to the client, which he can use to receive subsidies or for energy performance cert...

Airtight buildings require airtight windows. To date little information is available on the typical airtightness of window frames, and the aptitude of current regulatory performance levels for windows in respect to very airtight buildings is highly uncertain. Between 1997 and 2012, 437 windows were tested in laboratory conditions for certification;...

Theoretically estimated energy savings associated with better energy performance levels are rarely achieved in residential buildings. Part of this is explained by the higher indoor temperatures found at higher performance levels. Literature associates this temperature take-back with physical and behavioral causes: better insulated envelopes result...

In this paper a series of leakage tests is presented on extremely airtight dwellings, studying the durability of the airtightness level and the measurement uncertainty involved. All houses subjected to testing are certificated passive houses, meaning the maximum air leakage rate upon completion was n50 < 0.6 h⁻¹ air changes per hour at 50 Pa pressu...

Bottom-up residential building stock models are often based on a limited number of reference buildings simulated using the same simplified, single-zone calculation methods as those used for regulatory energy performance assessments. Those methods have the advantage of requiring fewer inputs than multi-zone methods, but they do not allow simulating...

This paper describes a pragmatic building information modelling approach for teaching about residential energy use and official energy performance. This approach was first tested in the context of a student exercise on design guidelines for nearly zero energy dwellings. In particular, we provide the details about the BIM approach and discuss severa...

The OLV Hemelvaart church in Watervliet dates back from the 16th century and contains valuable panel paintings and wooden artefacts. They need to be preserved in a stable conservation climate. However, due to the old air heating system, the indoor climate is not stable at all. The air heating system creates sudden strong rises in temperature and du...

Vacuum insulation panels (VIP) combine high thermal performance with minor thickness making them fit for building retrofit. However, consisting of a fumed silica core at low air pressure (near vacuum) encapsulated by a protective aluminum containing covering, they are prone to puncturing which inadvertedly increases the internal air pressure and th...

Examples of district heating systems are scarcely found in the Belgian housing sector. However in the current evolution towards renewable energy supply, district heating networks are seen as a promising solution. In 2013, the first phase of a low-temperature district heating system was used for the first time in the city of Kortrijk as part of a de...

GEOTABS combines a GEO-thermal heat pump with a Thermally Activated Building System (TABS). It is one of the most interesting technical solutions for energy efficient and healthy building. The study's objective is to research the characteristics of an optimized GEOTABS office building design. The two most important calculation methods used are the...

The first year commissioning activities in 4 multi-family buildings from a zero-carbon neighbourhood is presented, with focus on the operation of the ventilation systems, the indoor climate and user acceptance. The key parameters to detect the main system failures are identified and the effect of the detected defects and failures on the energy perf...

In many countries, the theoretical heating demand within the official energy performance assessment of houses is evaluated using simplified, single-zone quasi-steady state models, based on ISO 13790 and considering one standard, average user profile. Unpredictable variations in user behavior are acknowledged as a major cause of varying prediction e...

The thermal performance of window frames can easily be calculated using 2D numerical simulations. Several commercial software packages are available, and international standards provide a clear methodology to calculate the thermal transmittance. However, even though these methods are well known in academia and the research community in general, the...

The application of energy monitoring in buildings brings along an increasing availability of measurements of the energy flows and temperatures in buildings at rather short time intervals. By processing these measurement data using system identification techniques, the thermal characteristics of the building envelope can be unveiled. In this paper,...

Wind-driven rain (WDR) is one of the most important causes for water damage in buildings. Therefore, the first crucial step to assess the hygrothermal performance of the building envelope, is the appropriate estimation of the amount of rainwater striking the building's façade. ISO 15927 offers the annual average index –mainly to assess the moisture...

The Belgian building stock is characterised by a vast amount of houses with non-insulated cavity walls, creating high potential for blown-in retrofit cavity wall insulation. Although retrofit insulation is becoming standard practice, there is a prevalent uncertainty about test procedures and evaluation standards. Moreover, hardly any information is...

One of the most commonly used strategies to reduce the heating demand in low energy buildings is reducing the leakage level of the building envelope. Dedicated ventilation systems are then installed to compensate for the reduced air change rate in an energy efficient way. Most occupants, however, operate their ventilation system at very low flow ra...

This paper presents an investigation carried out for evaluating the dynamic thermal performance of a residential house using a multi-zone building model simulated with the help of TRNSYS 17. The building model integrates systems such as an air–air heat exchanger (AAHE), a water–air heat exchanger (WAHE) coupled with an earth–water heat exchanger (E...

How accurately can official energy performance calculations assess the real energy use in high-performance houses? This question was investigated by analysing 537 dwellings. Data on building characteristics and calculated performance from the Flemish Energy Performance of Buildings (EPB) database were complemented with data from energy utilities an...

Cavity walls are a widely used external wall type in north-western Europe with a good moisture tolerance in cool humid climates. In this work, a cavity wall configuration with a brick veneer outside leaf and a wood fibre board inside leaf is analysed with a newly developed coupled computational fluid dynamics–heat, air and moisture model. Drying of...

De techniek van na-isolatie van ongeïsoleerde spouwmuren laat toe om de thermische prestaties van bestaande gebouwen op een pragmatische manier te verbeteren zonder hinder voor bewoners. Niet elke spouwmuur is echter geschikt voor na-isolatie, en niet alle isolatieproducten komen er voor in aanmerking. De gerealiseerde prestaties zijn verder afhank...

Dynamic multi-zone energy simulations are required to design and evaluate natural/hybrid night ventilation, but the additional costs are too high, especially for smaller construction projects. That is why Ghent University and consultancy Ingenium designed a simulation tool for ventilation manufacturer Duco Ventilation & Sun Control with which the c...

Moisture-related damage is an important issue when looking at the performance of building envelopes. In order to accurately predict the moisture behaviour of building components, building designers can resort to Heat, Air and Moisture (HAM) models. In this paper a newly developed heat and mass transfer model that is implemented in a 3D finite volum...

Nowadays, the hygrothermal performance of the building envelope is often evaluated using HAM (heat, air and moisture) models. These models can be used to predict the hygrothermal response of the building envelope and can assist in reducing the risk of any moisture-related damage (e.g. decrease of thermal insulation value due to wetting, interstitia...

Airtight construction lies at the heart of achieving high energy performance in dwellings. But how well does it apply in new construction? This paper presents results from airtightness measurements on 44 randomly selected, standard new built single family houses in Belgium and from 4 case studies including 78 additional measurements. The houses wer...

With buildings achieving leakage levels of less than 10% of what they were only a few decades ago, infiltration losses are effectively mitigated. The flipside of the medal here is that the indoor air quality in such buildings is virtually exclusively depending on the performance of a dedicated ventilation system. This paper presents leakage rates a...

The specific behaviour of sleeping persons can greatly impact exposure. One such behaviour is the adoption of occluding bedding arrangements. In this study we focus on the increased rebreathing caused by sleeping with the head under the covers and the physiological responses to the changes in blood gas exchange this entails. 10 healthy adult test s...

Computational fluid dynamics (CFD) plays an increasingly important role in the design, analysis and optimization of engineering systems. However, CFD does not necessarily provide reliable results. The most crucial numerical solution error is caused by inadequate grid resolution, and the key modelling error sources in CFD in ventilated indoor enviro...

The main aim of ventilation is to guarantee a good indoor air quality, related to the energy consumed for heating and fan(s). Active or passive heat recovery systems seem to focus on the reduction of heating consumption at the expense of fan electricity consumption and maintenance. In this study, demandcontrolled mechanical extract ventilation syst...

Most zero-energy concepts focus on a reduction of the non-renewable operational energy use in buildings rather than taking the reduction of their life cycle energy use as a starting point. Nevertheless, the life cycle embodied and end-of-life energy will become more important, especially in buildings with low operational energy. Therefore, the life...

The potential systemic differences in performance of natural, exhaust and mechanical ventilation in dwellings is the object of relentless debate among scientists, industry and policy makers, although comparisons found in literature often fail to compare the different systems on an equal basis. Presenting the results from a multi zone simulation bas...

Sizing rules in residential ventilation standards lack uniformity in both methodology and resulting design flow rates. Additionally, mere comparison of design flow rates is case sensitive and, due to effects of infiltration, adventitious ventilation and occupancy, ill-suited to assess performance of an exhaust ventilation system with regard to the...

There is very little information about human exposure to gaseous indoor air pollutants in the sleeping environment, even though the conditions in this environment are at least worrisome. The exposure during sleep is characterized by long exposure time, both absolute and relative, prevalence of specific pollutants and uncustomary proximity of source...

Energy performance regulations for buildings are continuously updated. Projections within the future are being made, fixing now what will be the standards for new buildings for the following decades. The construction sector itself is also evolving, trying not only to follow those new rules, but often trying to look ahead, developing, testing and la...

Only recently energy efficiency and reduced cooling energy consumption have become a primary concern for many European countries. Consequently, the corresponding cooling technologies and calculation methods have not yet received the necessary attention in national energy performance regulations. For example, only few countries impose some kind of s...

Unforeseen variations in user behaviour can cause large differences between real and predicted heating demands in dwellings. While these discrepancies have been extensively documented in the literature, taking user behaviour into account in energy calculations remains challenging and could benefit from additional knowledge of the inhabitantstextquo...

In the transition towards a low-carbon society, the application of district heating systems is reconsidered. The new interest entails a lot of questions about district heating design and performance, especially in combination with contemporary dwellings that have a reduced space heating demand. This study presents the simulation results that suppor...

Night cooling, especially in offices, attracts growing interest. Unfortunately, building designers face considerable problems with the case-specific convective heat transfer by night. The multizone building energy simulation programs they use actually need extra input, from either costly experiments or computational fluid dynamics (CFD) simulations...

Moisture storage and the associated heat and moisture transport in buildings have a large impact on the building envelope durability, the energy consumption in buildings and the indoor climate. Nowadays HAM (Heat, Air and Moisture transport) models are widely used to simulate and predict the effect of these transport phenomena in detail. Recently t...

Indoor air pollution has a negative impact on human health, comfort and productivity. Emissions, however, are often related to essential functions of the indoor environment and cannot be eliminated with source control. Ventilation is then used to dilute these pollutants to acceptable concentrations.Due to recent crises in the energy markets and the...

Multizone building energy simulation (BES) programs become popular among building designers. They include a wide variety of techniques and advanced heat transfer models, yet require only limited computational time. Unfortunately, the use of correlations to predict the convective heat transfer undermines their reliability. The available correlations...

The predominant boundary conditions for evaluating watertightness of a wall are pressure difference across and water spray rate on the wall. However, the relation between these key climatic effects as defined in standards or actual weathering conditions remain, as yet, undefined. A comprehensive calculation method to define correct boundary conditi...

In recent decades there has been an increased focus on enhanced thermal resistance of building components and as a consequence, the relative importance of airtightness on the overall energy losses of buildings has increased significantly. The construction industry requires practical information on the airtightness of individual construction element...