Condensation in flat roofs under non-steady-state conditions

Vos, B. H.

doi:10.1016/0007-3628(71)90030-2

Cited by 7 publications

(3 citation statements)

References 1 publication

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“…The past decades, calculation methods to predict moisture behaviour of building components have improved significantly. These hygrothermal building envelope models originally evolved from the Glaser-method, a one-dimensional hand calculation method for vapour diffusion through insulated components (Glaser, 1958; Hens, 1976; Vos, 1971). Including heat and moisture capacity, liquid water transport and air transport, numerical heat, air and moisture (HAM) models have been developed accounting for different moisture sources such as wind driven rain, leakage, rising damp, initial moisture, interstitial condensation and surface condensation (e.g.…”

Section: Introductionmentioning

confidence: 99%

The impact of wooden studs on the moisture risk of timber frame constructions

Roels

Tijskens

2022

Journal of Building Physics

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Since timber frame constructions can help to reduce CO2-emissions and lower the embodied energy of buildings, the market share of timber-based buildings is growing across Europe. Unfortunately, timber frame constructions are found to be susceptible to moisture damage, such as interstitial condensation, mould growth and wood rot. To avoid moisture damage, a correct design of the wall composition is crucial, with special emphasis on the ratio between vapour resistance of wind and vapour barrier. Given that experimental investigations are time-consuming and expensive, numerical tools are common to assess the hygrothermal behaviour of building components. And although timber frame constructions are inherently two- or even three-dimensional due to the embedded wooden elements, most often, 1D-simulations focussing on the basic configuration with insulation between wind and vapour barrier are conducted. This paper investigates to what extent neglecting the embedded wooden elements influences the risk assessment of the wall. Three different wall configurations have been considered and their hygrothermal response, as predicted by 1D- and 2D-numerical simulations, are compared. Variability of the exterior climate is included by using four distinct different climate regions. Contrary to common assumptions, buffering of moisture in wooden elements does not always lower the risk on moisture damage, but might even increase it. While the predicted risk on mould growth was found to be similar between 1D and 2D-simulations, the opposite was found for the risk on interstitial condensation. Mainly for cold climates and wall configurations with hardly any other hygric buffering capacity, levels of interstitial condensation were found to be significantly higher when taking the wooden elements into account in the numerical simulations. Hence, care should be taken when assessing the reliability of timber frame walls based on 1D-simulations only.

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Section: Introductionmentioning

confidence: 99%

The impact of wooden studs on the moisture risk of timber frame constructions

Roels

Tijskens

2022

Journal of Building Physics

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“…None of the conditions were met, yet the simplicity of the Glaser approach was charming. This attracted the researcher's interest in upgrading the Glaser method in the years following the 1950s, with significant contributions from Vos in 1969 and 1971 [106,107] and Hens in 1975 and1978 [108,109], Van der Kooi in 1971 [110], and Kieβl in 1983 [111].…”

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confidence: 99%

Exploring Historical Perspectives in Building Hygrothermal Models: A Comprehensive Review

Jalili,

Ouahbi,

Eid

et al. 2024

Buildings

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The necessity of understanding and simulating hydrological phenomena as well as their interactions and the effect of anthropogenic and climate conditions on the ecosystem have encouraged researchers for years to investigate the moisture transfer in soil. Considering the moisture transfer as an isothermal phenomenon might cause a wrong estimation due to the non-isothermal nature of the moisture movement in porous media. Hygrothermal (coupled heat and moisture transfer) models are quite diverse and are the engine of the various hygrothermal software tools used to analyze the heat and moisture in building envelopes, drying technologies, and many other applications. This paper is a literature survey conducted to provide an overview on the classical hygrothermal models to address the historical perspectives on these models. First, it investigated, from a historical point of view, the challenges behind the development of hygrothermal models as unsaturated flow theories, beginning with Buckingham theory. The non-isothermal nature of moisture was the starting point for researchers to deal with new challenges during mathematical modeling and experimental analysis. In general, the theory of coupled heat and moisture transfer first developed by J.R. Philip and De Vries and the authors in the mid-1950s inspired the novel hygrothermal models, including Sophocleous and Milly’s model, Rode’s model, Künzel’s model, and Grunewal’s model. In a parallel of hygrothermal model developments, the models of Whitaker and Luikov can also be classified as hygrothermal models; they were mostly applied in modeling the phenomenon of drying. The study highlights the application of hygrothermal models in building physics and gathered a summary of international efforts such as Annex 24, Annex 41, and the HAMSTAD project and advancements performed from the classical dew point or steady-state Glaser method. Moreover, this study emphasizes the advantages of the standard of EN 15026 and limitations of the Glaser method. To sum up, hygrothermal models are still under development based on various assumptions of moisture driving potentials and transfer coefficients.

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“…These problems depend on many factors, but mainly on the hydrothermal properties of materials and on indoor and outdoor air temperatures and relative humidity. Building construction thermal bridging has been topic of many investigations [17][18][19] but the common tubular light guides have not been studied in detail in terms of temperature and air flow profiles. …”

Section: Introductionmentioning

confidence: 99%

Thermal CFD Analysis of Tubular Light Guides

2013

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Tubular light guides are applicable for daylighting of windowless areas in buildings. Despite their many positive indoor climate aspects they can also present some problems with heat losses and condensation. A computer CFD model focused on the evaluation of temperature distribution and air flow inside tubular light guides of different dimensions was studied. The physical model of the tested light guides of lengths more than 0.60 m proves shows that Rayleigh numbers are adequate for a turbulent air flow. The turbulent model was applied despite the small heat flux differences between the turbulent and laminar model. The CFD simulations resulted into conclusions that the growing ratio of length/diameter increases the heat transmission loss/linear transmittance as much as by 50 percent. Tubular light guides of smaller diameters have lower heat transmission losses compared to the wider ones of the same lengths with the same outdoor temperature being taken into account. The simulation results confirmed the thermal bridge effect of the tubular light guide tube inside the insulated flat roof details. The thermal transmittance of the studied light guides in the whole roof area was substituted with the point thermal bridges. This substitution gives possibility for simple thermal evaluation of the tubular light pipes in roof constructions.

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Condensation in flat roofs under non-steady-state conditions

Cited by 7 publications

References 1 publication

The impact of wooden studs on the moisture risk of timber frame constructions

The impact of wooden studs on the moisture risk of timber frame constructions

Exploring Historical Perspectives in Building Hygrothermal Models: A Comprehensive Review

Thermal CFD Analysis of Tubular Light Guides

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