The Impact of Roof Pitch and Ceiling Insulation on Cooling Load of Naturally-Ventilated Attics

Wang, Shimin; Shen, Zhigang; Gu, Linxia

doi:10.3390/en5072178

Cited by 8 publications

(5 citation statements)

References 18 publications

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“…Non-uniform triangular grids are employed, and the boundaries are inflated with nodes tightly clustered near the walls to ensure that the y + value for the first grid close to the walls is everywhere less than 1, in order to best capture the details of boundary layers, including the viscous sublayer which typically has a thickness of y + ~ 10. The numerical model employed in this paper is validated through grid and time step dependence tests as well as detailed comparison to previous experimental and large eddy simulation results of a benchmark problem of mixed turbulent convection in a square cavity [32][33][34], as reported in [29], where the same numerical model is employed to investigate the effects of roof pitch and ceiling insulation on attic cooling load and air flow.…”

Section: Numerical Modelmentioning

confidence: 99%

“…The roof-top temperature of T rt = 345.15 K specified in this study is corresponding to a typical peak roof temperature in summer days at several geographical regions in the United States, as evident in field measurements [4,30,31] and modeling predictions [21]. More discussions on the bases for the parameters chosen in the simulation can be found in [22], while the impacts of roof pitch and ceiling insulation on attic cooling load were reported in [29].…”

Section: Numerical Modelmentioning

confidence: 99%

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Impacts of Ventilation Ratio and Vent Balance on Cooling Load and Air Flow of Naturally Ventilated Attics

Wang

Shen

2012

Energies

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Abstract:The impacts of ventilation ratio and vent balance on cooling load and air flow of naturally ventilated attics are studied in this paper using an unsteady computational fluid dynamics (CFD) model. Buoyancy-driven turbulent ventilations in attics of gable-roof residential buildings are simulated for typical summer conditions. Ventilation ratios from 1/400 to 1/25 combined with both balanced and unbalanced vent configurations are investigated. The modeling results show that the air flows in the attics are steady and exhibit a general streamline pattern that is qualitatively insensitive to the variations in ventilation ratio and vent configuration. The predicted temperature fields are characterized by thermal stratification, except for the soffit regions. It is demonstrated that an increase in ventilation ratio will reduce attic cooling load. Compared with unbalanced vent configurations, balanced attic ventilation is shown to be the optimal solution in both maximizing ventilating flow rate and minimizing cooling load for attics with ventilation ratio lower than 1/100. For attics with ventilation ratios greater than 1/67, a configuration of large ridge vent with small soffit vent favors ventilating air flow enhancement, while a configuration of small ridge vent with large soffit vent results in the lowest cooling energy consumption.

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Section: Numerical Modelmentioning

confidence: 99%

Section: Numerical Modelmentioning

confidence: 99%

Impacts of Ventilation Ratio and Vent Balance on Cooling Load and Air Flow of Naturally Ventilated Attics

Wang

Shen

2012

Energies

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“…In terms of the building geometry, the lower the building surface area to volume ratio, the lower the heat gain would be, so for a given volume, building with a spherical shape is more energy efficient than a typical cubic building in terms of heating and cooling requirements. Accordingly, a dome house has 30% less surface area than a similarly sized box house, which means one-third less heat transfer to and from its surroundings, resulting in an average of 30% savings on the cooling and heating bill [7,8].…”

Section: Introductionmentioning

confidence: 99%

Computational Analysis of Natural Ventilation Flows in Geodesic Dome Building in Hot Climates

2016

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For centuries, dome roofs were used in traditional houses in hot regions such as the Middle East and Mediterranean basin due to its thermal advantages, structural benefits and availability of construction materials. This article presents the computational modelling of the wind-and buoyancy-induced ventilation in a geodesic dome building in a hot climate. The airflow and temperature distributions and ventilation flow rates were predicted using Computational Fluid Dynamics (CFD). The three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations were solved using the CFD tool ANSYS FLUENT15. The standard k-epsilon was used as turbulence model. The modelling was verified using grid sensitivity and flux balance analysis. In order to validate the modelling method used in the current study, additional simulation of a similar domed-roof building was conducted for comparison. For wind-induced ventilation, the dome building was modelled with upper roof vents. For buoyancy-induced ventilation, the geometry was modelled with roof vents and also with two windows open in the lower level. The results showed that using the upper roof openings as a natural ventilation strategy during winter periods is advantageous and could reduce the indoor temperature and also introduce fresh air. The results also revealed that natural ventilation using roof vents cannot satisfy thermal requirements during hot summer periods and complementary cooling solutions should be considered. The analysis showed that buoyancy-induced ventilation model can still generate air movement inside the building during periods with no or very low wind.

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“…Pitched roofs have insufficient heat accumulation, which results in overheating in the attic space [48]. Skylights also create visual discomfort.…”

Section: Figurementioning

confidence: 99%

Influence of Roof Windows Area Changes on the Classroom Indoor Climate in the Attic Space: A Case Study

et al. 2020

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Windows are a complex part of building design and provide a considerable benefit, including to school buildings. For the evaluation of the daylighting conditions prevailing in classrooms, the daylight factor (DF) was considered as the most appropriate parameter for indicating the quantity of admitted daylight. The DF values and CIE overcast sky were calculated using Velux Daylight Visualizer 3 software. The task of the paper is to compare various roof window openings in relation to the level of daylight in the attic, looking to optimize the use of the attic for teaching. The indoor air temperature has a general influence on comfort in the interior, in addition to daylight. In winter, the situation is not critical. The thermal insulation properties of packaging structures are sufficient. The situation is worse in summer, due to the fact that the heat-storage properties are undersized and there is excessive overheating of the indoor air. Four variants of roof windows and their influence on the overall microclimate in the attic are compared. The variant without roof windows is a suitable solution with regard to minimum overheating, but the worst situation for daylight. In order to receive even more light from the window (by moving windows to the top of the roof), we can use variant 2. Based on a combination of daylight calculations and summer temperature, a graphical dependence on window size prediction in terms of top and combined lighting is derived. This was hypothesized without shading the windows. Of course, the shading elements of these windows or cooling are expected in the summer. Finally, the energy required for cooling is compared depending on the size of the windows and achievement of the permissible temperature.

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The Impact of Roof Pitch and Ceiling Insulation on Cooling Load of Naturally-Ventilated Attics

Cited by 8 publications

References 18 publications

Impacts of Ventilation Ratio and Vent Balance on Cooling Load and Air Flow of Naturally Ventilated Attics

Impacts of Ventilation Ratio and Vent Balance on Cooling Load and Air Flow of Naturally Ventilated Attics

Computational Analysis of Natural Ventilation Flows in Geodesic Dome Building in Hot Climates

Influence of Roof Windows Area Changes on the Classroom Indoor Climate in the Attic Space: A Case Study

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