Parametric Louver System

12.14.2021 Noah Kelly1 Design Technology Manager Brittney L. Holmes1 Design Technology Specialist, Associate AIA

Parametric Louver System DESIGN TECHNOLOGY

HMC DIGITAL PRACTICE

Parametric Louver System

Noah Kelly1 Design Technology Manager Brittney L. Holmes1 Design Technology Specialist, Associate AIA

Digital Practice HMC Architects 12.14.2021 Abstract:

The Parametric Louver System is a customized tool that expedites several design iterations while embedding multiple design parameters, parametrically. The ambition of this paper to provide insight and a step by step pseudocode that displays workflows and knowledge to the AEC community. Our methodology targeted the global approach that aims to provide quantifiable design solutions based on environmental and geometric standards. Then develop the tool from a bottom up

approach using the louver system specifications.

Both the overall design aesthetic and functionality are critical. Our study revealed that setting up the definition must properly reflect the intent of how the script will be used. The logic and sequence of operations will be dependent on one another. This work has advanced our knowledge and in house serves to provide detailed and effective solutions based on the design teams needs at HMC.

Keywords: Design, Technology, Parametricism, Visual Scripting, Façade, Louvers, Automation

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4-8 Panel Types

Fig G.1: Louver angle set-up

Fig G.1.1: Louver angle set-up

Digital Practice is a group within HMC Architects that aims to support project ambitions by applying design technologies and techniques.

It exists to leverage advanced digital design tools that create the best product and experience for our clients and users across multiple offices.

Digital Practice is multi-faceted and prioritizes people through digital transformation. Investing in state-of-the-art tools and furthering education to improve the technical literacy of the company.

The task was to create a script that could produce, analyze, and optimize façade louver geometry; while allowing for designers’ input.

Digital practice started this process with a detailed tool development questionnaire developed inhouse that allows the team to gather project objectives, outcomes, timeline, and other critical pieces for a successful collaboration.

As we move into this facade study, it is important to remember that there are two parallel stories here: a geometric and environmental story.

The goals for the geometric story were to create a louver system that allowed for varying louver angles, density, and design input. The ambition for the environmental study was to help design a louver system that reduced the heat gain and glare within the program space. The design goal for this parametric tool envisioned the utilization of multiple iterations and flexibility within the design parameters set using the tool development questionnaire.

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E Sun Altitude informs optimal louver angle

Greater than, Less Than conditional statement based on program and distance to the louver.

4-8 Panel Types

Fig G.2: Louver angle set-up

The Geometric Story: Digital Practice collaborated across multiple departments which interlaced different sets of skill and expertise together. The parametric louver tool was developed in a way to support the design team to create multiple façade schemes instantaneously through an iterative process without the need to remodel any geometry. As well as test the performance of those iterations that respond to the performative targets defined by the Sustainable Design Group1. The design targets established were to maximize visibility based on the location of the program but also to minimize cooling loads from solar gain (Fig G.1, G1.1). The design baseline reflects seasonal conditions based on the Spring and Fall equinox (Fig G.2). The geometric parameters are defining three scales, the louver system, individual panels, and louvers.

The geometric configuration of the louver angle and density are largely contributing to reaching these design parameters (Fig G.3). To accomplish this design flexibility the parametric louver tool defines the panel type and quantity. Then within each panel the range of louver angles and louver quantity can be specified.

The tool development spanned a little over a month as careful deliberation and collaboration alongside the design team, Regenerative Design, and Digital Practice was necessary to output a viable solution. The defined scales are working as a unified system which results in a randomized pattern of louvers. The geometric configuration of louver angle and density are large contributors

The Sustainable Design Groups “goal at HMC is to change the way we think and approach architecture by [setting sustainability] resolutions that change how HMC sees the world and supports our shared belief that the environment is central to health, wellness, prosperity, and the communities we serve. HMC Architects, a signatory member of the American Institutes of Architects 2030 Challenge calls for all new buildings, developments, and major renovations to be carbon-neutral by 2030.”

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Fig G.3: Panel row organization set-up

Fig G.4: Louver angle set-up

to reaching these design parameters as well as the overall aesthetic appeal of the building (Fig G.4). The parametric louver tool integrated the design intent and budgeted linear feet of louvers to satisfy the client expectations. To validate the geometric configuration, environmental analysis was performed by embedding daylighting data into the tool.

The Environmental Story: The ability to conduct these environmental simulations is beneficial to provide quantifiable data to inform the design team, client, and thirdparty participants. Depending on the climate analysis required there are multiple metrics that can be analyzed. The Spatial Daylight Autonomy (sDA) and Annual Sunlight Exposure (ASE) metrics were used to test daylighting performance of the louver system. Running this analysis provides a clear result which informed the configuration of the panels. The metrics used for the louver performance analysis are established by the Leadership in Energy and Environmental Design (LEED). sDA is a metric that defines a percentage of area that meets a minimum daylighting illuminance for a specified time of the year.

ASE is a metric that identifies visual discomfort that does not exceed 10% of space with direct sunlight that has more than 1000 lux for a maximum period of 250 hours per year ASE1000/250” (p.233).

Fig R.1: System height and width

The Chabot Library is new construction and has followed the LEED 4.1 target recommendation based on regularly occupied space which achieves a 300/50% value of at least 55% for daylighting.

The glare percentage (ASE) solution target is 10%. Using the LEED 4.1 manual provides a clear description of environmental strategies to achieve thermal comfort. To represent the clearest sky it is suggested to use one day within 15 days of March and September 21st of the year. Multiple design solutions based on their ability to meet the LEED 4.1 standards were presented to the design team. Layering both the geometric parameters, occupant visibility, and environmental standards, the analysis performed at different iterations of the design informed the final direction.

The Approach: To achieve the final scheme, it was critical to include the louver properties in the design system.

The profile and span of the louver selected informed the panel width and density. The global design approach was established to maximize the performance of the Libraries South Façade which spanned 149’-0” linear feet (Fig. R.1). The louver system attaches to secondary frame which is a Galvanized HSS assembly that is connected to the primary structure (Fig. R.2). The parametric tool does not account for any assembly or connection details. However, the geometric parameter aligns with the secondary frame requirements. The distance between the outside exterior curtain wall of 3’-5“ accounts for a maintenance catwalk. The louver is an aluminum airfoil system that spans

defined parameter that assigns the angle of the louver to 15, 30, or 45 degrees. This is done to standardize the system based on the view range, light shelf, and louvers with minimal daylighting impact. This gives the designer full authorship to test different configurations to achieve the design ambition. The parameters within the panel types and louvers are as followed; panel type count, orientation to the façade, standardized angular properties, and louver density.

Fig R2: Generic System Detail

either 5’-0” or 10’-0” horizontally. This project is utilizing the 10’-0” louver span which attaches to a steel member for support. The curtain wall mullion spacing is also 5’-0” on center which neatly ties in both assemblies. The length of the south-west and south façade was divided into sixteen panel rows, and within those rows the team had identified an allowable max panel type count of six. Having worked alongside the design team to identify and test different panel types, the team selected the top 6 highest performing metrics, aesthetic, and programmatic requirements. The panel types are labeled A – F which can be assigned to any of the sixteen panel rows locations. The panels have a

When using any type of visual programming software, it is critical to clearly define the rules and parameters required to meet the ambition of the design goal. Without a clear roadmap the script outcome can deviate from the intent and may result with faulty or un-usable design solutions. Therefore, by clearly defining the project location, expectations of script usage, and design performance; the computational designer can clearly execute a script that will resolve the design problem.

The design team provided native rhino geometry that defined the width and height of the south-west and south façade to be referenced for the louver system. Before assigning the primitive Rhino geometry, within Grasshopper, confirm the surface geometry has the correct direction and is planar. It’s also important to verify the building geometry received with the teams most accurate model, which will most likely be the production model, as teams try to maintain multiple parallel models its inevitable for there to be geometric discrepancies. After confirming these items, it is

Fig. R.3: Facade Geometry Represenation (Brep)

Fig. R.4: Define the top and bottom polyline

time to set up the louver definition based on the design parameters that have been established.

The pseudocode for this louver assembly goes as follows: •

Define the area, on the façade, of where the louvers will be providing sunshade.

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Define base louver surface to work from

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Extract polyline from top and bottom of base louver surface

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Offset that polyline perpendicular to surface normal

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Divide polylines to create points that will be used to construct panel surfaces (in this case the constraint was at 10’-0” interval)

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Divide those panels vertically to define the louver placement

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Move louver divisions perpendicular to surface normal

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Create louver profile

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Design louver rotation logic

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Design panel type louver patterns

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Design system for applying panel types to panel slots on façade surface

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Extract system info for designer evaluation: density, total louver count, panel count, and louver horizontal datum count per panel

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Visualize Louver system in rhino

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Fig. R.5: Organize surface into rows

Louver System Complete

To define the façade surface area, define the Bounding Representation (Brep) (Fig. R.3) that will be the source for rationalizing the geometry into specified panel width. Deconstruct the Brep (DeBrep) into its component outputs to define the top and bottom edges of the façade (Fig. R.4, GH.1). The polyline geometry will allow us to offset the façade to meet the system requirements and generate the panelized geometry. To do this one must explode the top and bottom polyline to then divide the polyline into segments parametrically.

This collection of points will determine the louver

Fig. GH.1: Assign facade geometry and define the top and bottom edges

panel surface geometry using the component, 4Point Surface (Srf4PT) (Fig. R.5, GH.2). In this case, dividing the surface into 10’-0” segments result in sixteen panel rows.

Then Contour (Contour) (Fig. R.6). the 4Point Surface which will define the base louver geometry.

The system height was established by the building geometry which informed the distance value

Fig R.6: Use Countour to generate base geometry.

Fig. R.7: Move points to set louver depth.

Fig. R.8: Interpolate points to generate louver profile.

Fig. R.9: Loft curves to complete louver profile.

inch by a factor of twelve to acquire the appropriate result for geometry. By moving (Move) .08 in Unit-Z (Z) direction the point transformation component allows the four points to make the curve profile of the louver (Fig. R.7, GH.4). Then interpolate (IntCrv) (Fig. R.8) the vertices on both sides of the row. To complete the surface, loft both sides together (Fig. Fig GH2: Rebuilding the facade surface into 4PT Surface.

for the Contour component by dividing the total system height with the total louver count desired (Fig GH.4).

To generate the louver geometry profile, select the end points of the base profile of the louver. Then evaluate the curve to determine the end points

Fig GH.4: Setting louver depth R.9, GH.5).

The louvers must be organized into the correct Tree Structure and then partitioned it into 16 branches of 36 lengths items. These partition lists must be flattened in order standardize the

Fig GH.3: Deconstructing the original facade surface, the Contour component, will result in a the design quantity indicated by the number slider of louvers.

Fig GH.5: Creating points that define the louver profile

that will later inform the rotation. Confirm that the louver curves are reparametrize to reset all points to zero and one. Then move point in the same plane to create a line to generate the louvers curves on both the right and left side of the louver. Divide one

data points for later operations. This allows the scripts to parametrically adjust based on original façade surface length and height. The rotation of a louver can be defined within a range between zero to 45 degrees. By defining the angle, the radians

Fig. R.10: Rotate Louvers

will become an input to rotating the louvers threedimensionally. To rotate the louvers, we need to evaluate the original base curve that defines at the midpoint. Doing this will provide the rotation centroid and axis inputs to inform the, Rotate 3D (ROT3d) component (Fig. R.10, GH.6).

pattern logic to each panel location. In this case we used the Gene Pool component to define the panel type pattern logic, A - F, as defined in the

Fig GH.6: Setting up individual rotation for the louver system

Fig GH.7: Using the Gene Pool components to define the panel types

By utilizing the component, Gene Pool (Genes), one can graphically associate the louver design parameters that are organized into vertical categories by assigned the same quantity of line items to louver count (Fig Gh.7). The gene pool acts as a Boolean toggle (Toggle); a true false statement, which will determine the density or quantity of louvers per type. In this case, there are three categories that have clearly been defined: Light Shelf, View Range, and low impact zones.

From here we need to define the panel types that will be used, and then apply the panel type

Approach. In setting up the next portion of the script, it will be helpful to use the relay component to label and organize the component pieces. This portion of the script we will need to combine the panel types with the total panels defined on the façade. To define the removal logic of louvers per panel we will need to provide the pattern logic to a Cull Pattern component. The best way to define the panel type per panel on the façade will be to use a Stream Filter (Filter) component. This will allow one to toggle through multiple Gate Inputs

Fig. R.11: Use cull pattern to apply panel types

Fig. R.12: Final rendered louver geometry

setup. By defining the true false statement for louver density per panel type, the angle of the louvers, and panel type assignment are the key factors for the design outcome (Fig. R.12, GH.8).

Lastly, it is important to leverage the parameters within the script to extract the data points for analytics. The data that was pulled from this script tallied the density, total louver, and panel row count. To visualize the logic and data, Grasshopper provides the ability to showcase the data outputs and the final geometric design. One way to visualize the geometry is to utilize the Custom Preview (PreviewMat) and Custom Preview Line weights (PreviewLW). By including a Colo(u)r Swatch, the author can customize the graphical representation

Fig GH.8: Using Stream Filter and Cull Pattern to apply

Fig GH.9: Leveraging data within the script to read out louver density, total louver count, and total panel count

to select a pattern. In this case the pattern is the panel type. This step needs to be set up per panel row. Each of these components are duplicated 16 times to allow for independent panel row control.

The randomization of panel type is done by utilizing a cull pattern (Cull) defined between the configuration result from the panel type, and the predefined angle pattern that was done after defining the louver geometry (Fig. R.11). In conclusion, the initial Brep and the geometry division and organization is critical to the overall

Fig GH.10: Leveraging data to render data in the

of the geometry to best suit the design intent (Fig GH.9). Lastly, to expose the embedded data one can label with text the rows, louver count per row, angles associated with panel types, and overall quantites (Fig. Gh.10).

Next Steps: The future ambition of this script is to take the native Rhino geometry and convert into the Revit for documentation and further design coordination.

The script includes multiple parameters such as the louver panels types, quantities, and angles which can translate into Revit. There are multiple tools for interoperability, however the tool of choice is Rhino Inside. This application is a way to translate the primitive geometry from Rhino into Revit. The final product can be detailed and formalized using Rhino.Inside.Revit is an open source platform is a multi-directional software tool that allows native Rhino geometry generated from Grasshopper to import and export into other applications such as Revit. Utilizing the Grasshopper components that support the Revit data hierarchy will allow the ability to support Revit interaction. There are several components that support Revit families, filters, inputs, materials, and Revit types that will align properly with the Revit data structure. Allowing for full integration of scheduling, documentation, and addresses a variation in components such as site, walls, hosts, and parameters. Understanding the built, category, direct shape, document, element, filter, family, host, input, material, model, parameter, Revit primitives, room and area, site, type, view, and

wall components will be the interface that allows Rhino and Revit to communicate.

The future aim for Digital Practice at HMC is to create a workflow that automates the conversion of data from Rhino to Revit. The interoperability factor is key to designing in both software applications among many contributors. The technical goal set forth by the team was to create a louver panel family within Revit. To do so, the louver family in Revit needed to have the flexibility and control but also edited in Grasshopper. The type instance will need to be unique to each project implemented.

The parameters defined in Grasshopper should be translatable and adjustable. Therefore, the workflow from grasshopper to a Revit native element will have embedded grasshopper data.

Allowing complete flexibility between Grasshopper and Revit users and uses. Due to prohibited research and implementation time, the Chabot Library louver system used a Direct Shape component to allow the grasshopper geometry to translate into Revit. Even though the direct shape will translate the Rhino geometry to the Revit API structure, the geometry is essentially a dateless block. Revit will use the Direct Shape as a baked object from Rhino Inside that cannot be modified even though it is a Revit element. Direct Shape is a reasonable path if the geometry output does not have to be sophisticated or if there will be multiple iterations for quick design studies. This is not the final solution and does not display the full utilization of Rhino Inside, however Digital Practice is continuously developing further processes and research. Upon reflection the Parametric Louver

System tool can be enhanced by substituting out some of the components used in the workflow described in ‘The Approach’. While the script achieved the design ambition we realized thereafter that creating surface, by the 4Point Surface component, and then contouring that surface to retrieve the base geometry to generate the base geometry for each louver was an inefficient method. We believe that the best way to execute this portion of the pseudocode would be to use the points from the divided polyline to draw the vertical lines to represent the panels. Then divide those lines to generate the base louver geometry.

This will minimize processing time by eliminating potential heavy surface data.

In conclusion Digital Practice at HMC has tested the louver design system against environmental data per LEED 4.1 standards. Keeping true to the design ambition and parameters set forth from the, HMC Design Team, who carried out the construction documents and client relation. This algorithm was designed in a way that would allow multiple design iterations with ease to the design team. Furthermore, the Digital Practice group investigations of Rhino Inside workflows and design technology interoperability continues. The aim is to create a seamless workflow that utilizes full interoperability across multiple software platforms. Further investigation constitutes more research and deeper understanding of the Revit API structure and the Rhino Inside grasshopper components.

Additionally, the translation between visual programming to a web-based design tool, Hypar, is also being developed. This

tool allows for the non-design technology user and design technologist to collaborate using the actual parameters in real time. This is the next level of digital visualization and communication, where advance software tools dissolve potential technical barriers. Automation, efficiency, and interoperability will fuel further discoveries at HMC. Resulting in a contribution to the AEC community who can also use these tools.

References LEED 4.1 “LEED Link: LEED v4.1 Guides.” U.S. Green Building Council, www.usgbc.org/articles/leed-link-leed-v41guides.

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