[EnergyPlus_Support] Overhanging / Canopy like roof.

["benjamin_khuong@xxxxxxxxx [EnergyPlus_Support]" <EnergyPlus_Support@xxxxxxxxxxxxxxx>]

Hi,So i'm building an energy model that consist a roof that hangs over the south & west side of the house.
Now that roof that hangs over the house, has an air gap of about 6" to the actual home. I was curious to see how much difference there would be in having that 6" air gap as opposed to none. To my surprise, the difference is very little.

When the overhang is directly on top of the home, the annual cooling load is 12.465 million btu.
When the overhang is 6" above the hope, the annual cooling load is 12.148 million btu.

I was expecting the cooling load to be much lower for two main reasons.

1. with the air gap the upper ceiling of the home will be shaded and no in contact with direct sunlight.

2. convection between the overhang and roof of the home.

When the overhang is directly on top of the home, wouldn't there be more heat transferred through conduction?

Why is the difference so little? I was thinking because during night radiation heat would get trapped under the overhang. Not sure if that's enough to keep the annual cooling load from dropping.

Thanks! 

Ben K.

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Posted by: benjamin_khuong@xxxxxxxxx

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