Hygrothermal behaviour of timber frame walls finished with a brick veneer cladding

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 conditions: in winter a vapour open wind barrier is appropriate, in summer a more vapour tight. Therefore, similar walls but with different types of wind barrier have been investigated. In one set-up a vapour open bituminous impregnated wood fibre board is used as wind barrier, whereas in the second set-up a more vapour tight wood fibre cement board is used. The study shows that a high relative humidity can be expected at the interface between insulation and wind barrier during winter conditions, leading to a high mould growth index. In contrast, the relative humidity at the interface between insulation and inner vapour retarder during summer is lower than expected. This can be caused by the buffering capacity of the hygroscopic materials in the wall

On the drying potential of cavity ventilation behind brick veneer cladding : a detailed field study

© 2017 Elsevier Ltd 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 therefore crucial. In the current study detailed field experiments have been conducted in Belgium to study cavity ventilation behind brick veneer cladding. A simplified version of a South-West oriented cavity wall finished with brick veneer cladding has been analysed regarding the airflow pattern inside the cavity and the cavity's hygrothermal conditions. In this way, the drying potential of cavity ventilation behind brick veneer cladding can be assessed. For the dataset considered in the present article, the study showed that buoyancy induced cavity ventilation leads to a higher effective air change rate compared to cavity ventilation due to wind pressure. Furthermore, it was found that cavity ventilation is not of great help to dry out the whole outer leaf. However, it proved to lower the moisture levels inside the cavity, which – if e.g. the brick veneer is combined with a wooden loadbearing wall – might be important to avoid mould growth problems. The study also showed that climatic conditions play an important role in the drying potential: sunny but windless days have larger drying potential than cloudy but windy days.status: publishe

Modelling insulated coving's potential to reducing thermal bridging and moisture risk in solid wall dwellings retrofitted with external wall insulation

© 2017 Elsevier LtdMould growth and surface condensation are problems for many dwellings, and the retrofitting of insulation can increase the risk of these occurring. This is especially the case for historical solid wall properties receiving external wall insulation (EWI), which often have architectural details at the roof eaves that cause discontinuities in the insulation and so can result in excessive thermal bridging. This paper presents the results of an investigation into retrofitted solid wall properties where modelling is used to investigate the problem and effectiveness of insulated coving products which are designed to reducing thermal bridging. Thermal modelling is undertaken to establish the optimum design to reduce risk. The insulated coving was found to be effective in reducing thermal bridging in all the scenarios investigated and to reduce moisture risks occurring in some solid walls situations

Feasibility of Exterior Air Barriers in Timber Frame Construction (Haalbaarheid van externe luchtschermen in houtskeletbouw)

The primary objective of the present work is assessing the feasibility of exterior air barrier systems in highly insulated timber frame construction. The first part of this thesis presents in situ and laboratory measurements that verify whether acceptable airtightness levels can be achieved through improving the continuity of the wind barrier. These investigations quantify typical air leakage paths in such systems and, further, shed light on the practical aspects of its execution. The second part of the study examines the hygrothermal behaviour of lightweight elements with an exterior air barrier. This aspect covers both experimental and numerical work and is restricted to wall elements only. A new vertical hotbox/coldbox test setup was applied to simulate the hygrothermal performance of full-scale walls under controlled climate conditions. In addition to these measurements, the study examined the onset of interstitial condensation on hygroscopic and/or capillary active air barrier materials on smaller test specimens. The thesis at hand will further outline a numerical modelling strategy to assess the heat, air and moisture (HAM) transport in lightweight walls. Herein, strong emphasis lies in the evaluation of the presented modelling approach with a combination of benchmarks from the literature and the experimental data obtained in this work. Finally, annual numerical simulations assessing the hygrothermal performance of exterior air barriers in cold and moderate climates will be presented. A parameter study will examine the (1) behaviour of various wall assemblies, (2) identify the impact of bad workmanship and (3) illustrate its behaviour in several European climates.status: publishe

Experimental analysis of cavity ventilation behind rainscreen cladding systems: A comparison of four measuring techniques

© 2015 Elsevier Ltd. The present article elaborates on the comparison of four measuring techniques quantifying the ventilation rate behind typical cladding systems in wall elements. In total eight full-scale test walls have been investigated in a test building located in a maritime temperate climate (Belgium). Two different commonly used cladding systems are studied: (a) brick veneer and (b) fibre cement sidings. The test walls were installed on the Southwest and Northeast façades of the building corresponding to the orientations with most extreme exposure regarding solar radiation, wind directions and wind-driven rain. In total four different measurement techniques to quantify the ventilation rate in these systems have been applied: a) tracer gas techniques, b) indirect method based on pressure measurements, c) direct method based on anemometers and d) method based temperature and relative humidity registration. The results indicate that the ventilation rate behind vented brick veneer is two orders of magnitude lower than behind ventilated cladding systems with sidings. It was found that the most appropriate measuring technique of a wall system is depending on the ventilation rate, and hence on the type of cladding. For brick veneer claddings, the method deriving the air flow rate from the pressure gauges was found to be most suitable. In the wall systems with sidings, on the other hand, the ventilation rates were sufficiently high to be measured accurately with the anemometers.publisher: Elsevier articletitle: Experimental analysis of cavity ventilation behind rainscreen cladding systems: A comparison of four measuring techniques journaltitle: Building and Environment articlelink: http://dx.doi.org/10.1016/j.buildenv.2015.01.030 content_type: article copyright: Copyright © 2015 Elsevier Ltd. All rights reserved.status: publishe

What are the hygrothermal consequences of applying exterior airbarriers in timber frame construction in Europe?

© 2014, International Building Performance Simulation Association (IBPSA). Moisture-induced damage is one of the major causes of degradations and reduced thermal performance in wood frame buildings. It is therefore crucial to incorporate the hygrothermal assessment of new timber frame building envelopes systems from the early development phase onwards. The article at hand presents the simulation results studying the hygrothermal performance of various timber frame wall configurations with exterior air barrier systems. A parameter analysis explores the impact of different European climates, insulation materials, exterior air barrier materials and verifies in addition to the impact of bad workmanship in the installation of the insulation layer. This study reveals that the application of mineral wool (MW) insulated timber frame walls in combination with exterior air barriers results in increased moisture loads. Moreover, small air gap channels between the MW and the adjacent exterior air barrier significantly increase natural convection and add up to harmful moisture levels. Yet the simulations indicate that the use of blown-in cellulose insulation can avoid these issues. The study further indicates that the technique of exterior air barrier is more suitable for continental climates rather than for moderate sea climates in Europe.peerreview_statement: The publishing and review policy for this title is described in its Aims & Scope. aims_and_scope_url: http://www.tandfonline.com/action/journalInformation?show=aimsScope&journalCode=tbps20status: publishe

Highly insulated pitched roofs resilient to air flow patterns: Guidelines based on a literature review

© 2016 Published by Elsevier B.V. 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 barrier systems to guarantee the thermal and hygric performance by the exclusion of exfiltration is widely acknowledged today, less emphasis is put on the necessity of a continuous wind barrier to prevent wind-washing of the insulation layer. Also the effects of small air leakages around the insulation layer which can trigger natural convection is currently underestimated in practice. Based on findings in the literature, guidelines are put forward on how to construct a pitched roof with a robust high thermal performance.publisher: Elsevier articletitle: Highly insulated pitched roofs resilient to air flow patterns: Guidelines based on a literature review journaltitle: Energy and Buildings articlelink: http://dx.doi.org/10.1016/j.enbuild.2016.03.071 content_type: article copyright: © 2016 Elsevier B.V. All rights reserved.status: publishe

Pneumomediastinum as a complication of esophageal intramural pseudodiverticulosis

Dysphagia is a common complaint of patients seen at the outpatient clinic as well as at the emergency room. We report esophageal intramural pseudodiverticulosis (EIPD) as a cause of dysphagia that is less known by physicians and it is rarely described in the literature. EIPD is characterized by multiple, segmental or diffuse, flask-like outpouchings in the esophageal wall corresponding to dilated and inflamed excretory ducts of the submucosal esophageal glands. The underlying etiology remains unclear. Esophageal strictures, esophageal candidiasis and gastroesophageal reflux disease are often associated. The diagnosis can be made by upper gastrointestinal endoscopy, but barium esophagography is the modality of choice. Complications of EIPD are rare and include broncho-esophageal and esophagomediastinal fistula, pleural and pericardial effusion, abscesses, gastrointestinal bleeding from a web-like stenosis or esophageal perforation with pneumomediastinum. The treatment for EIPD should be directed towards treating underlying associated conditions and relieving symptoms rather than the pseudodiverticulosis itself

Numerical and experimental investigation of the hygrothermal response of timber frame walls with an exterior air barrier

status: publishe