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[TRNSYS-users] Re : Re: external shading factor (multizone building)

I asked about this before and I'm forwarding you the answer I got and was valid when i tested the influence of my blinds on the heating/cooling energy necessary for the building.

hope this is useful.

Best regards,


Message original Re : Re: [TRNSYS-users] Blinds

De : Adrien JEZEQUEL - ITF <a.jezequel@itf.biz>
A : trnsys-users@cae.wisc.edu
Date : 2010-06-22 15:44:27

Dear Julie,

I suggest you to put an equation tool outside of Type56. In that equation tool, ESHAD (the ratio of non transparent area of the shading device to the whole glazing area, as defined in TRNBUILD) will be calculated depending on blinds position.
If you consider that :
  • GWINDOW = solar shading factor of window only, which is constant (60% for example, which means that 60% of solar radiation goes through the window)
  • FS = solar shading factor of your system Window + Shadings.
    FS depends on blinds use,
    • if blinds are used, FS = 0.2 (for example)
    • if not, FS = GWINDOW
In that way, FS is calculated as the product between :
  • the amount of solar energy which pass through external shading device when they're used => (1-ESHAD)
    • ESHAD = 0 means no shading
    • ESHAD = 1 means zero transmission
  • and window solar shading factor (GWINDOW)
    • FS = GWINDOW.(1-ESHAD)    (1)
      Regarding (1)
      ESHAD = (1- FS/GWINDOW)   (2)
No you have a relation between ESHAD, FS and Window G-Value :
  • When blinds are up, solar radiation are only blocked by the window solar shading factor => FS = GWINDOW and ESHAD = 0.
  • When blinds are down, solar radiation are blocked by window and external shadings => FS = 0.2 (for the whole system in that example), ESHAD = (1-0.2/0.6) = 0.667 that means that 66.67% non transparent area of the shading device to the whole glazing area)
    Regarding (1) FS = 0.5*(1-0.0.667) = 0.5*0.4 = 0.2 which is the total shading factor you want.
Best
 www.itf.biz
www.itf.biz
 Adrien JEZEQUEL
Simulations Thermiques Dynamiques
ITF
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Message original Re : Re: [TRNSYS-users] external shading factor (multizone building)

De : Knut Erik Enerstvedt <knut.erik.enerstvedt@gmail.com>
A : joke.d@vkgroup.be
Date : 2010-11-04 09:33:18

Joke,


I think you should only consider the g-value of the shading device when calculating external shading factor. The g-value

of the window is handled separately. So if the g-value of your shading device is 0.23, the external shading

factor becomes 1 - 0.23 = 0.77.


Someone please correct me if I am wrong.


Kind regards,

Knut Erik Enerstvedt



>Dear trnsys-users,

 

>I’ve a question about how to calculate the external shading factor (multizone building). Is the following correct?

 

>Suppose I’ve a window with a g-value of 0,37 and a g-value of 0,23 (external shading device + window).

>The external shading factor becomes then: 1 – (gwindow+shadingdevice/ gwindow) = 1- (0.23/0.37) = 0.38

 

 

>Kind regards,

 

>Joke De Beuckelaer

>project engineer mep