Formula driven panel variation in Revit

Component variation in Revit

In this exercise it will be shown a quite unconventional way to achieve a curtain panel family variation without recurring to either scripting or API. Usually this kind of solution is obtained by manually varying a parameter value for each one of the family components that are employed in a certain curtain wall system. As an example a handful technique is described here in Zach’s outstanding blog which uses a parameter with incremental values to achieve variation. Here it is another example still using the incremental values technique and addressing solar radiation performance more closely.

While the incremental techniques can be quite good to quickly and easily develop a parametric model than can respond to some sort of performance criteria, still it can prove to be troublesome to manually edit the value of hundreds of components. The other option would require to intervene with scripting to edit these values or employing API which surely would be the most efficient way. However not always programming is an available option at first when we are still exploring what are the design variables we need to manipulate.

The method I am going to present uses different tools some new and some old into a unique workflow which you will realise it is more a workaround but still can give an interesting and easy approach to performance driven design at the very beginning of concept stage which employs the Revit/Vasari user interface only.

 

All steps are strongly tied to each other and the design concept which develops  follows from the tools used and that particular sequence.  The overall workflow is breakdown as below

1. Design context and Solar exposure analysis
2. Facade panel subdivision using the Repeater Tool feature from Revit 2013
3. Curtain Pattern based family component design
4. Use of Reporting parameter and formulas to drive variation

 

The Design context

The design context for this exercise comprises two box shaped building as shown in the image below. Each of the building has same footprint and approximately 40×40 mt, one is oriented south-north while the other is around 40° from north, higher and  partially overshadowing the other. This is just a case study for a facade that presents an uneven solar exposure pattern due to shadowing of surrounding buildings. The resulting solar exposure on the south facade for the shorter building shows a linear gradient from left to right as shown in the pictures below.

 

 

 

 The component design strategy

The tools used here have a great impact on how the overall design it is developed. The two main concepts are these

• Create a double skin facade with varying depth
• Varying the panel opening size to allow more or less solar radiation to hit the south facade of the building

The overall goal is to create a design solution that can adapt and even out the solar radiation pattern on the facade. This results in a design solution that is uneven as well and precisely has a linear variation (for this particular case). Where the solar radiation is minimum to allow more light to enter the building the facade depth will be minimum (less than 50cm ) but the opening size bigger. On the other hand where solar radiation is maximum the depth  (over 3 mt)  will be increased while the opening size will be reduced. The idea is to use the depth to control the solar rays while the opening will be used as a diaphragm to compensate for more or less light.  This is a small example showing how a very simple design context can affect the design of a building component – or to say in other words (fancy) how a global condition affects a local condition.

 

Varying facade depth

 

 The Revit tools

In Revit/Vasari this is accomplished using the following tools

• A double skin mass family with 3 parameters controlling the depth (min, max and mid) in 3 vertices
• A pattern based curtain family to model the single component made up of 8 vertices
• The repeater tool
• An reported parameter which will change opening size according to facade depth (with a formula)

Ok all this might seem a bit complicated. Indeed it is but relatively simpler if coding is not in your pocket. The weirdest thing in this approach which is the key feature too is that I really needed to use a formula with a reported parameter. The only way to do this at the moment is to use a pattern based curtain panel family because it has hosted elements and this is not possible to make with just an adaptive component. However as you will see in the video the pattern based curtain panel will be used as an adaptive component. The other odd thing is that I needed 8 points to populate the component across the two subdivided surface and the only way to achieve this is to use an octagon based pattern!

 

 

 

The Video

 

 

 The outcome

The technique used can prove to be quite useful at very early stage of design when addressing building performance with regard to solar radiation and daylighting.  The possibility to explore the potential of varying the depth of a double skin facade for environmental performance it is surely one of the great advantages of the illustrated technique. Indeed the legacy between tools (repeater tool and reported parameters driven formulas) and  design solution can prove quite powerful to open to novel and creative approaches to design performance. Lastly, the use of reported paramters and and formulas can be a quite useful approach to generate components variations without recurring to API/scripting/addins especially at the very early stages.  Of course, this methods has its own shortfalls

• Flexibility can be an issue as only curtain pattern based family can use reported parameters in formulas. The application of adaptive components could allow more flexibility.  Please Autodesk fix this if possible.
• Lack of more advanced tools in Revit to assess flawlessly  the performance of daylighting (like DF)  or radiations levels due to shading components. At moment quite annoyingly the model needs to be exported back and forth in other software like Ecotect.
• Having more simulation tools available within Vasari would allow the optimisation process while designing more direct control. It would be great the possibility to link performance parameters to geometry parameters for a truly performance based approach.
• For more precise control of the component geometrical variables responsiveness scripting/coding  is still the only solution. This is especially true if you consider computational performance.  Alternatively a similar results can be achieved also with the Parameters from Image addins - I leave the application of this tool for another post.

Below are shown some screenshots of a quick comparative analytical study between a facade with fixed depth / opening size and one with varying depth / opening size.

 

Fixed depth and opening size

varying depth and opening size

 

solar radiation level for a flat shading device

solar radiations level for a facade varying depth and opening size

 

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This entry was posted on Saturday, December 29th, 2012 at 12:55 am. It is filed under Tooling and tagged with adaptive points, Ecotect, Revit, solar insolation, Vasari. You can follow any responses to this entry through the RSS 2.0 feed.