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UHIE & TEMPERATURE

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Message 1 of 4
swaminathan.s
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UHIE & TEMPERATURE

We need to know the temperature rise due to Urban Heat Island Effect in the following cases;
 
1.      Total Plot Area of                    : 120 Acres.
Total Building Footprint          : 95% of above
Landscape                               : 5% of Plot Area
Roof SRI                                   : 40%
 
2.      Total Plot Area of                    : 120 Acres.
Total Building Footprint          : 90% of above
Landscape                               : 10% of Plot Area
Roof SRI                                   : 80%
 
Looking forward your support,

 

Whether it is possible through ecotect or any other software. Please help me.
 

3 REPLIES 3
Message 2 of 4
Pennetier1
in reply to: swaminathan.s

Hi swaminathan.s, 

 

Unfortunately, this is not something you could model with a thermal engine such as Ecotect as these software require enclosed volume of air to derive any temperature fluctuation from the given outdoor temperatures (from the weather file).

 

But you can certainly do a quick comparison study between your two options, assuming the general albedo of landscape cover is 0.20:

 

Option A: (0.05*0.20)+(0.95*0.40) = 0.35 average reflectivity of the plot.

Option B: (0.10*0.20) + (0.90*0.80) = 0.74 average reflectivity of the plot.

 

Solar absorbtion of option A: 1 - 0.35 = 0.65

Solar absorbtion of option B: 1 - 0.74 = 0.26

 

So option A absorbs (0.65-0.26)/0.26 = 150% more solar radiation than option B.

How to translate this into a temperature rise is anyone's guess.  I wouldn't know, but it would of course has to do with the actual ambiant outdoor temperature.  

Also, this would not account for the emissivity of the materials; most construction materials have a high emissivity (~0.9), which means they would re-radiate whatever heat they have absobed in the form of infra-red radiation.  Most metals have a very low emissivity (~0.05) which means that they tend to retain whatever energy they have absorbed and do not readily re-radiate that heat (that is why metals that are in the sun feel so hot to the touch).  Most roof constructions would fall in the first category, thus re-radiating up to 90% of the heat they have absorbed to the ambiant air.

 

Altough that does not directly answer your question, I hope this helps a bit.

Let me know if you have more questions on this topic, otherwise please accept as a solution so that others can benefit from this information.

Cheers,

Olivier A. PENNETIER

SYMPHYSIS

www.symphysis.net

Message 3 of 4
swaminathan.s
in reply to: Pennetier1

Is there any spread sheet calculator. 

Message 4 of 4
Pennetier1
in reply to: swaminathan.s

Hi swaminathan.s, 

Unfortunately, I do not know of any spreadsheet calculator for Heat Island Effect. You might be able to develop something yourself, utilizing your roof's material albedo index and emissivity, to derive some sort of comparative studies as described in my first post.

 

Cheers,

Olivier A. PENNETIER

SYMPHYSIS

www.symphysis.net

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