Re: [EnergyPlus_Support] The SHGC is always different from what I enter! Please help!

["jeannieboef@xxxxxxxxx" <jeannieboef@xxxxxxxxx>]

If you want more accuracy, you will have to use the complex fenestration inputs. The e+ simple glazing method reverse engineers a best fit complex glazing from your simple inputs. IMO the accuracy of the glazing is good. A SHGC difference of 0.07 between two real glazing assemblies is very small. However, 7% difference on solar gains is large. If you can't use the complex method, you could consider changing the glazed area slightly.

Mit freundlichen GrüÃ?en- Sent from my iPhone (excuse the brevity)

i. A.

Jean Marais

b.i.g. bechtold

Tel.   +49 30 6706662-23

On 05.03.2014, at 12:08, <hisham.rashrash@xxxxxxxxx> wrote:

 

Dear all,

I have noticed that no matter what SHGC value I enter in idf file, I always get a different value in the output, for example: I put 0.36 in idf editor, and for one simulation case I get the output to show 0.355 instead, and for another case I get 0.362, even if these two cases have only some u-values different for some constructions!

I am preparing a report that studies the effect of envelope on external heat gains, and half the building envelope is glass, this small difference in SHGC is changing the savings by too much!

I have tried changing the time step from 2 to 6 to increase accuracy, but it is all in vain!

I also noticed that when I reduced USI-values for glass (from 1.61 to 1.4) and for walls (from 0.24 to 0.215) EnergyPlus changed my SHGC from 0.355 to 0.362 (non of them is what I entered 0.36) and the savings in heat gains are reduced from 8% to 3% when using lower U-Values!!!

Please help!

Hisham.

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