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© 2016 Informa UK Limited, trading as Taylor & Francis Group. 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, needs to withstand severe outdoor weather conditions and maintain pre-defined air permeability values. The aim of the present article is to investigate the impact of severe climatic conditions on the airtightness of typical taped joints. The airtightness of 32 wood fibre cement board samples has been investigated. Each specimen has a 2 mm wide joint. Two different kinds of commercially available tapes were used to seal these joints. Airtightness of all specimens has been tested before and after accelerated ageing procedures that mimic real exterior climate conditions. Three different ageing protocols were selected: (1) temperature cycles, (2) temperature, rain and frost cycles and (3) UV exposure alternate with high humid conditions. The present paper discusses the durability of the two tapes by comparing the air permeability of the specimens before and after accelerated ageing exposure. The results indicate that for both tapes tested the impact of the three artificial ageing methods on the air permeability is limited (increment less than 2 × 10−5 m3/m/h/Pa). 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=tjov20 ispartof: International Journal of Ventilation vol:16 issue:1 pages:30-41 status: published

© 2015 The Authors. Throughout the years, different numerical HAM-simulation tools have been developed to assess and predict the heat, air and moisture response of building components. But, though commercially available and commonly applied in building practice, still, several simplifications and shortcomings exist in the common models. Probably the most important one, is the fact that most tools neglect or strongly simplify air transport, focusing only on heat and moisture transport. Especially for the analysis of wood frame constructions, these simplified models may cause a large discrepancy between simulation results and real performance. This study aims at a comparison of the outcomes of numerical HAM-simulations for wood frame constructions with experimental data of real test cases. In particular, the focus of this paper is on cavity ventilation behind brick veneer. Therefore, a simplified version of a wood frame wall with brick veneer cladding is studied in this paper. Different common modelling assumptions are compared. Furthermore, a detailed measuring campaign has been conducted at the VLIET test building of the KU Leuven to validate the different modelling approaches. By verifying the results of the numerical simulations by the data of real test cases, the reliability of the modelling assumptions can be analysed. The results of this study clearly show that simplified assumptions on cavity ventilation in HAM-models might cause large discrepancies between simulation results and in-situ measurements. publisher: Elsevier articletitle: Modelling Cavity Ventilation Behind Brick Veneer Cladding: How Reliable are the Common Assumptions? journaltitle: Energy Procedia articlelink: http://dx.doi.org/10.1016/j.egypro.2015.11.172 content_type: article copyright: Copyright © 2015 The Authors. Published by Elsevier Ltd. ispartof: pages:1467-1477 ispartof: Energy Procedia vol:78 pages:1467-1477 ispartof: IBPC 2015 location:Turijn date:14 Jun - 17 Jun 2015 status: published

© 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=tbps20 ispartof: Journal of Building Performance Simulation vol:8 issue:3 pages:1-22 status: published

Laboratory tests and numerical simulations to study the hygrothermal consequences of using an exterior air barrier in light-weight building envelopes are discussed. Full-scale test walls are placed between a vertical hot and coldbox, operating at controlled temperatures, humidity levels and total air pressures. The test walls are exposed to different boundary conditions during five consecutive measuring stages. Each test wall is provided with 18 thermocouples, 15 relative humidity, 3 heat flux and 1 pressure gauge sensor, covering the most important positions of the wall. In this way, the obtained results can be used as detailed validation data for heat, air and moisture (HAM)-models with a strong focus on natural and forced air convection. The main emphasis of this article is the evaluation of a numerical model with the current dataset. The model used is a modified version of DELPHIN 5 including a quasi-steady state airflow model with the ability to capture natural convection.

The current paper presents the results of a detailed laboratory experiment to study the hygrothermal behaviour of vertical light weight walls with an exterior air barrier. Four independent test walls (each 2.3 m by 0.5 m) are placed between a newly developed hot and cold box, operating at controlled temperatures, humidities and air pressures. All four walls are insulated with 30 cm of standard mineral wool to which OSB is applied as interior vapour retarder. The test walls differ from each other by the physical properties of applied exterior air barrier; airtightness, moisture buffer capacity, vapour permeability and thermal resistance. An additional objective of the current investigation is to generate validation data for numerical HAM models. As a consequence, great care was given to create precise two dimensional conditions and to minimize air leakages. The results reveal that using an exterior air barrier instead of traditional interior one, may increase the moisture load as a result of buoyancy driven convection. This leads to an increased risk for mold growth and interstitial condensation against the upper position of the exterior sheathing in winter conditions. © 2012 Elsevier Ltd. ispartof: Building and Environment vol:56 issue:10 pages:192-202 status: published

The article presents detailed experimental results on the hygrothermal performance of various ventilation cavities. In total 8 full-scale test walls have been installed in a test house to study the impact of different cladding materials (fibre cement sidings/brick veneer cladding) and the size of ventilation openings on the conditions in the cavity. Two measuring methods, hot bead anemometry and air pressure registration, are used to investigate the ventilation rate within the cavities configurations. In addition, equipment was installed to monitor the effect of the ventilation rate on the temperature and humidity conditions within the walls. The results indicate that the air change rate behind brick veneer (1-10ACH) is typically two orders of magnitude smaller than the ventilation behind wall systems with sidings (>100-ACH).