staf roels | KU Leuven (original) (raw)

Papers by staf roels

ABSTRACT Regarding the retrofit of existing buildings, exterior thermal insulation systems are ge... more ABSTRACT Regarding the retrofit of existing buildings, exterior thermal insulation systems are generally considered as a good solution and their advantages result in an optimal hygrothermal performance of the building facade. However, with respect to the renovation of a building facade, interior insulation is often the only possible retrofitting solution, due to architectural, esthetical or economical reasons. In current building practice, the use of hygrothermal simulation for the design of an interior insulation system is often considered as relatively complex and intensive. Alternatively, guidelines and recommendations to assist building engi-neers and designers with the application of interior insulation have been developed in Germany (WTA), and in Denmark (Videncenter for energibesparelser i bygninger). In this paper, an assessment and design method for the interior insulation of masonry walls, recently published in Belgium, is presented. The method focuses on the analysis and diagnosis of the existing building facade. The stepwise approach intends to help the building engineer and architect with the design of the interior insulation.

Materials and Structures Materiaux Et Constructions, Mar 1, 2001

The hygrothermal performances of building zones, building components and building occupants are s... more The hygrothermal performances of building zones, building components and building occupants are strongly related to the interior humidity, and this is in turn related to the moisture buffering by the interior enclosure. This paper presents a methodology for the characterisation of the moisture buffer potential of a single interior element, by introduction of the production-adapted MBV*. It is shown that this weighted-average of a long-and a shortterm value allows dependably characterising the moisture buffer potential for a multitude of moisture production schemes. As such, the introduced MBV* yields a dependable characterisation of single-element moisture buffer potential, which allows direct qualitative comparison of different elements and which can be measured by simple and fast measurement techniques and equipment. It extension towards the room enclosure level, and its ensuing use for quantification, is the topic of the companion paper .

Wood in building wall assemblies may come in contact with liquid water. Rain, as the main source ... more Wood in building wall assemblies may come in contact with liquid water. Rain, as the main source of water, is expected to be shed by the wood cladding. Improper detailing may result in water entering the wall, reaching the wood sheathing or even the wood frame cavity. Traditional methods like capillary uptake provide some indication of the process of liquid movement in wood but cannot convey the role of the wood structure in the water entry, redistribution and drying processes. This paper presents qualitative results using X-ray images to view moisture distribution within wood during liquid uptake. The microstructure of wood and the direction of grain are shown to influence the pattern and rate of moisture movement.

... 1. Hogeschool voor Wetenschap en Kunst, Department of Architecture Sint Lucas B-9000 Gent, Be... more ... 1. Hogeschool voor Wetenschap en Kunst, Department of Architecture Sint Lucas B-9000 Gent, Belgium 2. Belgian Building Research Institute (BBRI), Division of Building Physics and Indoor Climate, B-1342 Limelette, Belgium 3. Katholieke Universiteit Leuven, Laboratory of ...

To analyse the hygric buffering capacities of gypsum board, sorption isotherm and vapour permeabi... more To analyse the hygric buffering capacities of gypsum board, sorption isotherm and vapour permeability are determined for the different layers: the finishing coat, the paper at front and back side and the interior gypsum layer. The obtained information is used to simulate the dynamic moisture balance of a small room with gypsumboard as finishing material. The influence of gypsum board on the hygric response of the room was found to be of minor importance. Moreover, once coated the hygric buffering was mainly limited to the coat itself and became almost negligible.

In numerical simulations of the heat, air and moisture response of building enclosures, wind-driv... more In numerical simulations of the heat, air and moisture response of building enclosures, wind-driven rain (WDR) is commonly assumed to be equally distributed over the material surface and implemented as a constant flux during a certain period. In reality, WDR is a discrete phenome- non, with individual rain drops hitting the building facade. In this paper the WDR load and the valid- ity of the spatially averaging model are investigated both experimentally and numerically. For the experimental study, a new set-up has been developed, which is able to measure the evolution in time of WDR load, absorption, evaporation and runoff at the material surface. In the numerical part the classical one-dimensional averaging approach is compared with a three-dimensional discrete ap- proach. This allows to verify the accuracy of the current numerical simulation that deals with wind- driven rain as a boundary condition.

This analysis aims at articulating a necessary level of detail in the formulation of the atmosphe... more This analysis aims at articulating a necessary level of detail in the formulation of the atmospheric moisture load for obtaining reliable building part moisture transfer simulations, by comparison of the simulated moisture responses of a ceramic brick cavity wall. It is shown that the correct estimation of a global magnitude of the wind-driven-rain coefficient α is most crucial in the modelling of the wind-driven-rain load. Its reduction to a constant value, to be used with hourly averaged climate data, should also take the influences of temporal averaging and α variability - with rainfall intensity and wind speed - into account though. For evaporative exchange, it is shown that the variations of the surface moisture and heat transfer coefficients with wind speed, and their overall order of magnitude, heavily influence the moisture response. The wind-driven-rain conclusions are rather material independent, the latter conclusion at the other hand may alter quantitatively for material...

DOI: 10.1177/109719639902200408 1999 22: 334 Journal of Building Physics Kenneth Strømdahl Morten... more DOI: 10.1177/109719639902200408 1999 22: 334 Journal of Building Physics Kenneth Strømdahl Morten Hjorslev Hansen, Geert Houvenaghel, Mårten Janz, Martin Krus and Interlaboratory Comparison of the Measurement of Retention Curves ... International Council for Research and ...

As wind-driven rain is one of the most important moisture sources for a building envelope, a reli... more As wind-driven rain is one of the most important moisture sources for a building envelope, a reliable prediction of the wind-driven rain load is a prerequisite to assess the durability of building facade components. To incorporate wind-driven rain in HAM models (heat, air and moisture), many factors should be taken into account. Not only building geometry, wind speed and wind direction, raindrop size distribution, etc. influence the rain load on buildings, but also phenomena such as raindrop impact, absorption, evaporation and runoff should be taken into account. The latter phenomena are however not yet incorporated in the current HAM-models. The present study focuses on the runoff and absorption of wind-driven rain on building facades. It couples a simplified runoff model with a HAM model. In a first part of this study, the model is briefly described. In the second part, the model is used to calculate the amount of runoff due to wind-driven rain during a two-shower rain event on di...

This paper gives an onset to whole building hygrothermal modelling of the interaction between int... more This paper gives an onset to whole building hygrothermal modelling of the interaction between interior and exterior climates via building enclosures, which even takes into account wind-driven rain (WDR). First, the temporal and spatial distribution of WDR on the facades of a single leaf brick wall building is numerically determined. Then the hygrothermal behaviour of the walls and the room zone is numerically analysed. The results show that WDR loads can have significant impacts on the indoor climate, energy consumption and mould growth risk.

ABSTRACT Regarding the retrofit of existing buildings, exterior thermal insulation systems are ge... more ABSTRACT Regarding the retrofit of existing buildings, exterior thermal insulation systems are generally considered as a good solution and their advantages result in an optimal hygrothermal performance of the building facade. However, with respect to the renovation of a building facade, interior insulation is often the only possible retrofitting solution, due to architectural, esthetical or economical reasons. In current building practice, the use of hygrothermal simulation for the design of an interior insulation system is often considered as relatively complex and intensive. Alternatively, guidelines and recommendations to assist building engi-neers and designers with the application of interior insulation have been developed in Germany (WTA), and in Denmark (Videncenter for energibesparelser i bygninger). In this paper, an assessment and design method for the interior insulation of masonry walls, recently published in Belgium, is presented. The method focuses on the analysis and diagnosis of the existing building facade. The stepwise approach intends to help the building engineer and architect with the design of the interior insulation.

Materials and Structures Materiaux Et Constructions, Mar 1, 2001

The hygrothermal performances of building zones, building components and building occupants are s... more The hygrothermal performances of building zones, building components and building occupants are strongly related to the interior humidity, and this is in turn related to the moisture buffering by the interior enclosure. This paper presents a methodology for the characterisation of the moisture buffer potential of a single interior element, by introduction of the production-adapted MBV*. It is shown that this weighted-average of a long-and a shortterm value allows dependably characterising the moisture buffer potential for a multitude of moisture production schemes. As such, the introduced MBV* yields a dependable characterisation of single-element moisture buffer potential, which allows direct qualitative comparison of different elements and which can be measured by simple and fast measurement techniques and equipment. It extension towards the room enclosure level, and its ensuing use for quantification, is the topic of the companion paper .

Wood in building wall assemblies may come in contact with liquid water. Rain, as the main source ... more Wood in building wall assemblies may come in contact with liquid water. Rain, as the main source of water, is expected to be shed by the wood cladding. Improper detailing may result in water entering the wall, reaching the wood sheathing or even the wood frame cavity. Traditional methods like capillary uptake provide some indication of the process of liquid movement in wood but cannot convey the role of the wood structure in the water entry, redistribution and drying processes. This paper presents qualitative results using X-ray images to view moisture distribution within wood during liquid uptake. The microstructure of wood and the direction of grain are shown to influence the pattern and rate of moisture movement.

... 1. Hogeschool voor Wetenschap en Kunst, Department of Architecture Sint Lucas B-9000 Gent, Be... more ... 1. Hogeschool voor Wetenschap en Kunst, Department of Architecture Sint Lucas B-9000 Gent, Belgium 2. Belgian Building Research Institute (BBRI), Division of Building Physics and Indoor Climate, B-1342 Limelette, Belgium 3. Katholieke Universiteit Leuven, Laboratory of ...

To analyse the hygric buffering capacities of gypsum board, sorption isotherm and vapour permeabi... more To analyse the hygric buffering capacities of gypsum board, sorption isotherm and vapour permeability are determined for the different layers: the finishing coat, the paper at front and back side and the interior gypsum layer. The obtained information is used to simulate the dynamic moisture balance of a small room with gypsumboard as finishing material. The influence of gypsum board on the hygric response of the room was found to be of minor importance. Moreover, once coated the hygric buffering was mainly limited to the coat itself and became almost negligible.

In numerical simulations of the heat, air and moisture response of building enclosures, wind-driv... more In numerical simulations of the heat, air and moisture response of building enclosures, wind-driven rain (WDR) is commonly assumed to be equally distributed over the material surface and implemented as a constant flux during a certain period. In reality, WDR is a discrete phenome- non, with individual rain drops hitting the building facade. In this paper the WDR load and the valid- ity of the spatially averaging model are investigated both experimentally and numerically. For the experimental study, a new set-up has been developed, which is able to measure the evolution in time of WDR load, absorption, evaporation and runoff at the material surface. In the numerical part the classical one-dimensional averaging approach is compared with a three-dimensional discrete ap- proach. This allows to verify the accuracy of the current numerical simulation that deals with wind- driven rain as a boundary condition.

This analysis aims at articulating a necessary level of detail in the formulation of the atmosphe... more This analysis aims at articulating a necessary level of detail in the formulation of the atmospheric moisture load for obtaining reliable building part moisture transfer simulations, by comparison of the simulated moisture responses of a ceramic brick cavity wall. It is shown that the correct estimation of a global magnitude of the wind-driven-rain coefficient α is most crucial in the modelling of the wind-driven-rain load. Its reduction to a constant value, to be used with hourly averaged climate data, should also take the influences of temporal averaging and α variability - with rainfall intensity and wind speed - into account though. For evaporative exchange, it is shown that the variations of the surface moisture and heat transfer coefficients with wind speed, and their overall order of magnitude, heavily influence the moisture response. The wind-driven-rain conclusions are rather material independent, the latter conclusion at the other hand may alter quantitatively for material...

DOI: 10.1177/109719639902200408 1999 22: 334 Journal of Building Physics Kenneth Strømdahl Morten... more DOI: 10.1177/109719639902200408 1999 22: 334 Journal of Building Physics Kenneth Strømdahl Morten Hjorslev Hansen, Geert Houvenaghel, Mårten Janz, Martin Krus and Interlaboratory Comparison of the Measurement of Retention Curves ... International Council for Research and ...

As wind-driven rain is one of the most important moisture sources for a building envelope, a reli... more As wind-driven rain is one of the most important moisture sources for a building envelope, a reliable prediction of the wind-driven rain load is a prerequisite to assess the durability of building facade components. To incorporate wind-driven rain in HAM models (heat, air and moisture), many factors should be taken into account. Not only building geometry, wind speed and wind direction, raindrop size distribution, etc. influence the rain load on buildings, but also phenomena such as raindrop impact, absorption, evaporation and runoff should be taken into account. The latter phenomena are however not yet incorporated in the current HAM-models. The present study focuses on the runoff and absorption of wind-driven rain on building facades. It couples a simplified runoff model with a HAM model. In a first part of this study, the model is briefly described. In the second part, the model is used to calculate the amount of runoff due to wind-driven rain during a two-shower rain event on di...

This paper gives an onset to whole building hygrothermal modelling of the interaction between int... more This paper gives an onset to whole building hygrothermal modelling of the interaction between interior and exterior climates via building enclosures, which even takes into account wind-driven rain (WDR). First, the temporal and spatial distribution of WDR on the facades of a single leaf brick wall building is numerically determined. Then the hygrothermal behaviour of the walls and the room zone is numerically analysed. The results show that WDR loads can have significant impacts on the indoor climate, energy consumption and mould growth risk.