Impact of Overhangs

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Folks,

Does anyone have good research data using simulations on the impact of
overhangs and shadings for a typical building?

I am having hard time convincing architects to reduce the glazing. They
will make it a glass building if they are given a chance.

I want to show them that for a 2 or 3 storied building with ton of
glazing and few feet of overhang will not help the cooling/heating loads
at all.

I would appreciate your input.

Thanks much.

Fareed Syed EIT, LEED(r) AP

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Fareed,

I don't have any "good research data", but from my simulation experience the overall wall U-value is very important to the energy use related to the building envelope. The shading does not improve the U-value. If you are comparing to ASHRAE 90.1, then the maximum glazing percentage is 40%. Any glazing beyond this point in the proposed building would be compared to solid wall in the baseline.

If this is the case, then the comparison of glazing to solid wall for the percentage over 40% glazing will definitely hurt your energy savings. The SHGC of solid wall is 0, and the U-value is 10 times better than insulated windows.

Scott

SCOTT PARKER PE, LEED AP

Folks,

Does anyone have good research data using simulations on the impact of overhangs and shadings for a typical building?

I am having hard time convincing architects to reduce the glazing. They will make it a glass building if they are given a chance.

I want to show them that for a 2 or 3 storied building with ton of glazing and few feet of overhang will not help the cooling/heating loads at all.

I would appreciate your input.

Thanks much.

Fareed Syed EIT, LEED? AP

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Fareed

Maria Kordjamshidi's picture
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Fareed
?
I have examined the effect of many parameters on the thermal performance of 6 typical houses (single storey and double storey houses) for a moderate climate of Sydney. a part of my report comes in the following for your consideration.
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"Adding an overhang above all windows improved annual thermal performance of the typical houses in conditioned mode. However, this was not the case for the houses in free running mode. The houses presented different patterns of annual thermal performance in the different modes, responding to increments in overhang width.
Increases in overhang width of 1m resulted in an average of 4.8% enhancement in the house?s annual thermal performance in conditioned mode. The same overhang generally caused 3.7% deterioration in annual free running performance, while a slight improvement was observed in thermal performance in some cases.? The reason for these different results is made clear when comparing the seasonal performances of each house in two different house modes.
When all the overhang widths were increased to 1m, the summer performance improved by an average of 26.6% in conditioned mode. The improvement decreased to an average of 8% for all houses in free running mode. The winter performance of the typical houses in this situation deteriorated by an average of 8.2% in conditioned mode and 11.7% in the free running mode. Thus the deterioration that was observed in the annual free running performance of some of the houses in response to the setting of overhang with a width of 1m for all windows would appear to owe more to deterioration in their winter performance and less improvement in their summer performance in free running mode than in conditioned mode."
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Hope this help
?
Maria
?

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Maria:

Excellent information.

Would you please describe what you mean by "free running mode"?

Thank you.

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