[EnergyPlus_Support] RE: RE: Shading of many overhangs and calculation time

Interesting question, to which I don't know the answer. However, be careful to correctly account for the thermal bridging effects in the wall surfaces due to the attatched balconies. This is construction detail dependant.

---In EnergyPlus_Support@xxxxxxxxxxxxxxx, <o.hans@...> wrote:

Hi Patrick,

it depends a bit on your building design. If the balconies are rectangular and easily related to the windows below, then Shading:Overhang will be the fastest to model and calculate. They are linked to a specific window and input is therefore simple.

"Detailed" always describes a shading object that may have a shape other than rectangular and a vertices count other than four. Shading:Zone:Detailed is therefore an option if more than one window are covered and/or the shape is non-rectangular.

Shading:Building is an object related to the building but not linked to any specific surface. Mostly used to describe an external object shading the building.

Oliver

---In energyplus_support@xxxxxxxxxxxxxxx, <jcrossett@...> wrote:

It would defiantly make a difference in model creation time, and also in optimizing your design scenarios.

------->With shading overhang you have the benefit of a symmetrical model where you could add all your shading in a ratio based method so it would be a global setting- might want to do so on a orientation basis.. Also shading detailed may involve many surfaces, the primary issue with long runtime. I am not so familar with shading building. Also you might consider use of controlled blinds.

Jeremiah D. Crossett | Senior Analyst | Phase Change Energy Solutions
120 E. Pritchard St. | Asheboro, NC 27203 | Mobile 503-688-8951

www.phasechange.com

On Thu, Nov 14, 2013 at 11:02 PM, Patrick Bivona <patrick.bivona@...> wrote:

Hello,

I'm working on a high-rise tower block. I'd like to model balcony overhangs that provide shading to the glazing below.

There are 3 objects I can think of using:

1. Shading:Building
2. Shading:Zone:Detailed
3. Shading:Overhang

Knowing that I have about 500 balcony overhangs, I'm wondering if there are significant differences in terms of calculation time between these 3 options.

My thinking is that a Shading:Overhang object is only shading the glazing it's attached to. Whereas, for the 2 other options, E+ has to calculate the effect of each shading surface on all the other building surfaces in view.

Does it make that much difference?

Many thanks,
Patrick