modelling external perforated shading screens

[ayesha]

I have a typical room geometry and i want to add an external perforated screen for shading, outside of the glazing. What is the best way to model a facade with a repetitive shape for the whole window (just not vertical or horizontal fins). It is single glazed with outside screens and it is not a double skin facade system either.

if i a volume outside the glazing as local shade it wont let me add windows or opening into it.

this is something i would want to make. http://farm4.staticflickr.com/3603/3452 ... 6ebb_o.jpg

And im doing this to run the apache sim for total building energy analysis.

[Complex Potential]

Hi Ayesha

Thermally there are three ways to approach this; one is massively time consuming and difficult, the other is quick but pretty crude and the third relies on third parties.

The difficult way is to actually build the external screen in its component parts by hand and set it all of the bits as local shades. This could be a nightmare.

The crude way is to just reduce the g value of the glass by a factor equivalent to the percentage of "hole" visible through the screen.

The third way is to find a pre-made screen geometry file similar to the one you want in a program like sketchup and then attempt to import it into IES but finding such a file could prove difficult.

Good luck.

CP

[RossThompson87]

Hi,

Just a word of warning but from my experience any glazing in a local shade element just gets treated as opaque as if it isn't there.

I use SketchUp for canopies etc. as you can export 0 thickness surfaces.

I even end up making some funny chessboard shaped surfaces to represent a transparent canopy of a certain g-value. Im not sure there is any other option in IES to even be close to accurate.

I think there is plenty of room for improvement in IES when it comes to canopies - perhaps one for the suggestion section.

Ross

[bootsam]

Ive done this before. I just made a narrow room and then glazed both sides. Each side glazing g value of 0.7. This replicated a 50% free area or a total g of 0.5. Crude but it worked.

[ayesha]

Thank you. I have been able to model screen as a local shading device. I ran radiance (apache with sensors) but when i am running apache sim (dynamic simulation) I was prompted with an error saying:
"Error: Toom many rooms on illuminance file."