Exterior Shading minimum size

asked 2019-05-24 16:01:08 -0500

Determinant
1149 ●2 ●8

updated 2019-05-27 15:27:52 -0500

__AmirRoth__

4436 ●5 ●17 http://bleedinggreenna...

I want to model the net solar gain of exterior louvers. Their dimensions and spacing can be relatively close. I want to be sure that despite their size, the shadowing and inter-reflections between slats gets accurately modeled such that the net solar gain on the interior space is accurate. (I'm aware of the BSDF alternative but am exploring straight geometry input as an alternative).

Does this statement in the Shadowing Module section of the Engineering Reference document mean that I can model shadow and reflection for exterior surfaces that are at least 1 mm between all vertices?

Note that the resolution on surfaces/shadowing is 1 mm – using resolution beyond that will result in truncation of the shadowing.

answered 2019-05-31 11:22:53 -0500

Samuel de Vries
346 ●2 ●6

I interpret this as a condition for truncating which goes for both the vertices of the input geometry in Shading:site:detailed as well as the vertices of the shadows which are projected from these surfaces. (not sure)

Using this modelling approach you will only get shadowing and a single reflection (so no inter-reflections between blinds). Also the accuracy really depends on your settings for the solar distribution and the polygon clipping algorithm which processes overlaps between shadows.

I would make sure set the Solar Distribution field withing the Building object to 'FullInteriorAndExteriorWithReflections' and also experiment with the 'Maximum Figures in Shadow Overlap Calculations' and the 'Calculation Frequency' fields withing the ShadowCalculation object.

Even then I would still have some doubts about using this modelling approach as I don't the exterior shading algorithms where developed with things like blinds in mind. A good way to test it would be to first consider a very simple case (straight blinds, at a particular angle) and model this using both the method/settings you have in mind as well as using WindowMaterial:Blind approach.