Attic baffle size and vent configuration impacts on attic ventilation

The international residential code (IRC) and most building codes in North America provide attic ventilation codes which allow a certain minimum venting area with an unblocked space by the ceiling insulation. Most of these codes have similar minimum venting ratio, minimum space gap between the roof s...

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Bibliographic Details
Published in:Building and environment 2015-07, Vol.89, p.28-37
Main Authors: Iffa, Emishaw, Tariku, Fitsum
Format: Article
Language:English
Subjects:
Air change per hour
Attic ventilation
Attics
Baffle size
Baffles
Ceilings
CFD
Construction
Insulation
Roofs
Sheathing
Solar gain
Vent configuration
Vents
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Summary:The international residential code (IRC) and most building codes in North America provide attic ventilation codes which allow a certain minimum venting area with an unblocked space by the ceiling insulation. Most of these codes have similar minimum venting ratio, minimum space gap between the roof sheathing and ceiling insulation and vent area location for similar climatic conditions. In this paper, the effects of varying the gap between roof sheathing and ceiling insulation (baffle size) and the locations of vent area under both summer and winter conditions are investigated. Three different baffle sizes and three different locations of the attic vent are used to study their effect on the air distribution and temperature profile inside the attic space. A CFD model is developed and validated using existing experimental measurements. Results show that increasing baffle size hugely affects the air distribution when the air flow is majorly driven by wind. The upper side roof vents have been located at three different locations and our findings show when the upper vent is placed the furthest from the ridge the Air Change per Hour (ACH) value in the attic increases but the air circulation is minimal in the top parts of the attic space and structural elements. •CFD model that evaluates effects of baffle size and vent location is developed.•In wind driven ventilation, increasing the baffle size increases the ACH.•Varying vent locations affects the air circulation rate and diluting attic air.•Effect of buoyancy is insignificant when the ventilation is majorly driven by wind.
ISSN:0360-1323
1873-684X
DOI:10.1016/j.buildenv.2015.01.028