Penetration of snow into roof constructions—Wind tunnel testing of different eave cover designs

Thiis, Thomas K.; Barfoed, Peter; Delpech, Philippe; Gustavsen, Arild; Hofseth, Vidar; Uvsløkk, Sivert; Virel, M. Dufresne de

doi:10.1016/j.jweia.2007.02.017

Cited by 6 publications

(7 citation statements)

References 2 publications

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“…The measured amount of water during C4 was rather low. Thiis, Barfoed et al (2007) also found that position of the ventilation opening towards the weather board was effective to reduce snow penetration to the roof compared to a position close to the cladding. Thiis, Barfoed et al (2007) also indicated that the snow concentration of the air entering the air channel decreased by increasing air pressure drop over the eaves construction Hence, the measurements must be seen in connection to snowindraft which might be a bigger practical issue to solve.…”

Section: Discussionmentioning

confidence: 84%

“…A detailed (and comprehensive) review of WDR research is given in (Blocken and Carmeliet 2004, Blocken, Abuku et al 2011, Kubilay, Derome et al 2014. Large deposition chambers where the air-flow velocity is reduced, have traditionally been recommended for ventilated wooden roofs (Thiis, Barfoed et al 2007). However, new trends in architecture calls for solutions with minimal roof overhangs and slender design of the eaves.…”

Section: Introductionmentioning

confidence: 99%

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Moisture robustness of eaves solutions for ventilated roofs: Experimental studies

Grynning

Asphaug

Gullbrekken

et al. 2019

Science and Technology for the Built Environment

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Ventilated pitched wooden roofs with eaves (roof overhangs) is a common building practice in the Scandinavian countries. The eaves are protecting the façade from rain, wind driven rain (WDR) and snow, and it covers the roof ventilation aperture. The eaves should be designed so that the least possible amounts of rainwater and snow enters the ventilation aperture between the roof cladding-and underlayer roofing. At the same time, adequate ventilation of the roof must be ensured to promote proper drying-out capabilities of the roof and to avoid problems of snow melt and ice formation at eaves and gutters during winter season. Small or almost nonexisting eaves is a trend in modern architecture. It is a common perception that such solutions are more vulnerable to moisture damages due to possible increase of water penetration into the roof aperture. The aim of the study is to experimentally investigate the moisture robustness of the described risk area and to find answers to how the design of eaves influence the amount of rain that is driven on to the underlayer roofing under the aperture in ventilated roofs. It was found that the amount of collected water in the different test series to a large extent are given by the water droplet size as well as the wind velocity inside the air cavity. The results from this study simulates an example of a rain event with heavy rain intensity and strong winds (storm). The test represents an example of a storm event with a given droplet size distribution. The results indicate that an increased pressure drop decreases the water ingress. Comparative tests showed that installation of a wire mesh largely decreases the measured water collection and the dynamic pressures inside the air cavity.

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Section: Discussionmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Moisture robustness of eaves solutions for ventilated roofs: Experimental studies

Grynning

Asphaug

Gullbrekken

et al. 2019

Science and Technology for the Built Environment

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“…By installing a fly net, the local loss coefficient corresponds approximately to 30 tile batten passings. Thiis et al (2007) showed that an increased local loss coefficient and thereby a reduction in the air velocity inside the air cavity was effective to reduce snow penetration into the air cavity.…”

Section: Eaves Designmentioning

confidence: 99%

Local loss coefficients inside air cavity of ventilated pitched roofs

Gullbrekken

Uvsløkk

Geving

et al. 2017

Journal of Building Physics

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Pitched roofs with a ventilated air cavity to avoid snow melt and ensure dry conditions beneath the roofing is a widely used construction in northern parts of Europe and America. The purpose of this study has been to determine pressure losses at the inlet (eaves) and inside the air cavity consisting of friction losses and passing of tile battens. These results are necessary to increase the accuracy of ventilation calculations of pitched roofs. Laboratory measurements, numerical analysis as well as calculations by use of empirical expressions have been used in the study. A large difference in the local loss coefficients depending on the edge design and height of the tile batten was found. The local loss coefficients of the round-edged tile battens was approximately 40 % lower than the local loss coefficients of the sharp-edged tile battens. Further, the local loss factor increased by increasing height of the tile batten. The numerical analysis was found to reliably reproduce the results from the measurements.

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“…In spite of dissatisfaction for some parameters, there are quite a few researchers that have gained significant results through the wind tunnel tests [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Wind Tunnel Test of Snow Redistribution on Roofs

Liao¹,

Li²,

Huang³

2017

dtetr

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A series of wind tunnel tests were carried out to predict snow distribution on roofs. A typical stepped roof and two gable roofs were investigated. Model snow depth distributions on the roofs were measured at various time intervals. The effects of velocity and wind direction were studied, and mass transport rates on the roofs were examined as well. The results show that, the saltation of particles decreases the turbulence intensity nearby the surface, and the effective aerodynamic roughness-lengths of the field are proportional to the 2nd power of the friction velocities. At the wind direction of 0°, the snow depth distribution on the stepped roof is well consistent with the field observation. Snow depth distributions on the stepped roof are quite unbalanced under oblique winds, especially at wind direction of 135°, the snow depth coefficients range from 0 to 1.7. The leeward side of the gable roofs may accumulate more snow at wind direction of 0°. The maximum coefficients are 1.7 and 1.2 for slope 10° and 20° respectively. The mean mass flux rates on the roofs are proportional to velocities, implying that the mass transport rate increases with the 3rd power of the friction velocity.

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Penetration of snow into roof constructions—Wind tunnel testing of different eave cover designs

Cited by 6 publications

References 2 publications

Moisture robustness of eaves solutions for ventilated roofs: Experimental studies

Moisture robustness of eaves solutions for ventilated roofs: Experimental studies

Local loss coefficients inside air cavity of ventilated pitched roofs

Wind Tunnel Test of Snow Redistribution on Roofs

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