Shading factor for heating and cooling loads calculation

[271000000]

There is shading factor for exterior blanck which says a value between 0 and 100 must be entered on construction type for the heating and cooling loads calculation, what is this, and how does the value choose.

[iainsavage]

I can't find a definitive definition for this but my understanding is that it is a rough estimate of the percentage effectiveness of external shading elements such as overhangs, brise soleil etc.

If you've actually modelled the geometry of shading devices in the building model then I don't think you would use this shading factor (leave it at default of zero).

Also unless you have a lot of deliberately designed effective shading devices on the building it might be safer to ignore any small/incidental shading so that your calculated loads are on the safe side.

There might be something in the EnergyPlus documentation which explains it better but in a quick scan I couldn't see any reference to it.

[271000000]

i tried it, if i increase this value (0 to 100), cooling load is decrease. So this value is for reduced to cooling loads. But must be carefull when there is this entering value. The other question is that how does this value determines? We must know shading area for selected space. For example, if selected space exterior area is %40 in shading effect (we must know that), we can entering 40 in the blanck

[iainsavage]

If you increase the value then you are adding shading effect which consequently reduces solar gain and that's why your cooling load has reduced.

I think this factor should only be used as a rough estimate in the analysis of rudimentary models.

If you have built a decent model of your building, including modelling any shading devices (window overhangs, brise soleil etc) then their shading effect would be calculated by the software, so adding more shading using the shading factor value would over-estimate the shading effect and under-estimate the solar gains.

I would treat this factor with caution and only apply a non-zero value if you are modelling the shading devices and you  know for sure that your building will have significant and effective shading added.

[handjonathan]

Hi @271000000 

Thanks a lot for posting your question to the forums!   Has the solution suggested by @iainsavage helped with your issue?
 
We look forward to hearing back from you with more information so we can help you as a community!