window shading devices

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Looking for a shortcut here-

I've got a building with lots of glazing, and for a typical 12'high by
24'long wall, there is a shading grid device with horizontal and
vertical mullions at 2'spacing (both horiz and vert). Is there an easier
way to model this than doing a series of 2'x2' windows ?

Is it possible to attach a shading grid to a building face?

Thanks

Kristin Gustafson EIT, LEED(r) GA

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Kristin,

You could create one window and then make the other windows "like" the first window using link-to existing. The window to reference will need to come before all other windows referencing it...

Or, this sounds like it might be curtain wall glazing. If so, you should be able to model a single window and create external shading devices to match the design. You will have to adjust coordinates to move the device close to the building fa?ade.

Kevin

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Taking Kevin's 2nd suggestion a bit further:

For a regular/repeating pattern as you're describing, the shading effects could quickly be approximated with a single building shade of a specified transmittance to reflect the mullions' coverage. There'd be a corresponding single glazing, with no frame and thermal properties defined to match the system as a whole.

~Nick

NICK CATON, P.E.

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Kristin,

You can use "Building Shades" to make your 2'x2' shade grid. In Detailed Edit go into the "Building Shell" module by clicking that button along the top. In the Component Tree on the left right-click on "Building Shades" and select "Create Building Shade..." Enter the dimensions in the dialog box that pops up, then on the next dialog box adjust the coordinates and tilt to place it where you want. Note that you can move the dialog box to the side (I move it to a second screen) and keep it open while you see the changes in the 3-D viewer as you go from field to field. Then I can see right away if a rotation in the wrong direction made it disappear inside the building, for example. Keep adding these shades until you have your grid. Good luck!

________________________________
Keith Swartz, P.E., LEED AP

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Nick,

While I agree that shading devices can be simplified as anything else in energy modeling, one should be careful to the extent this is applied. For example, I have had to simplify multiple shading devices to a single shade when doing load calculations in Trace. I think there were five 8" devices projecting from the fa?ade over a single storey and I combined them to one 0.75m shading projection. It would be fine for schematic. A LEED or EO111 submission would most likely have the correct shading config.

Kevin

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Hi Kevin!

I'm in partial agreement... I think we'd both agree the person in the best position to judge the appropriateness for a given approximation is the actual modeler. I'm only bringing up a single shade approach to help brainstorm the options available, not intended to be an exclusively "correct" position.

Regarding "blanket rules" for SD vs. "finished" LEED models, I can perhaps productively share for you and Kristin that I have used (and described in documentation) the technique I just described in a final LEED submission (which received 10/10 pts) with no questions raised on the matter. On the flip side, I have also encountered projects where the combination of overhangs and other shading elements demanded an exacting approach, and have encouraged/assisted others pursuing such levels of detail - evidenced in the archives.

Refining and improving a model to a point of "finished" is a case-by-case exercise that requires allocating limited time to different areas within the model - one project may require lots of attention to the shading/glazing systems where another may require that additional time be spent fine tuning the performance curves and scheduling to capture a hydronic systems' particulars. 90.1 and LEED afford the modeler latitude to make reasonable approximations in order to prioritize where to invest their time/efforts.

I personally wouldn't take any strategies of approximation completely off the table before understanding the project more intimately. Case in point: A recent list discussion involved a fellow sharing a model so massive in size that certain approximations (which I would rarely use in a smaller "finished" model) were a practical necessity, not an option!

A more general anecdote from the other side of the issue: Someone following me closely on the lists may have noticed I have a general aversion to using "unweighted" constructions wherever that doesn't match reality. I accept this as a personal quirk shaped by my own experience - but I'm careful to recognize what makes me feel comfortable for my own projects isn't sufficient grounds for judging others' decisions. Other modelers have backgrounds/knowledge that permit them to use an unweighted "approximation" more comfortably and with confidence in the resulting modeled behavior, and that's great!

Long story short - I'm not disagreeing with your suggested practice at all, but only that we leave the responsibility of judging approximations with the modeler ;).

~Nick

NICK CATON, P.E.

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..."finished" is a case-by-case exercise...

Absolutely! Thanks, Nick.

Kevin

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