a feast for the engineers eye

In Zuidwolde (The Netherlands), Metadecor is currently building a facade that plays with the eye and the perception of perspective. The engineers of Metadecor worked with a parametric design by ArchiTech Company (ATC) to compose the distorted three dimensional composition of wooden slats. When finished, the project will present itself as a rhythmically flowing object with a wooden skin. But behind it all, figuratively and literally, there is an ingenious concept using the latest digital tools in design and production. That is why this project is entered for the Construsoft BIM Awards 2023, that showcases projects designed with Tekla BIM software from all over the world.

Commissioned by Hesco Bouw, Metadecor engineered, produced and installed the 3D shaped wooden facade for the ‘Huus voor Sport en Cultuur Zuidwolde’. The building is a multifunctional accommodation that adds a library, theatre hall and care facilities to an existing sports hall. The skin of the building is an angular form of wooden slats that undulates around the complex, embracing the older and new parts of the accommodation.

The construction of the design started with a parametric design by ArchiTech Company (ATC). The engineers of Metadecor loaded the 3D wire model supplied by ATC into Grasshopper and enhanced it with various design criteria, such as profiles, slat dimensions, minimum and maximum distances, etcetera. The design was then linked to Tekla Structures for further (detailed) engineering details.

Facade design

The facade is made of mounting brackets that are connected to the insulated facade. Aluminium tube trusses are mounted in these brackets. Prefab frames are positioned between the aluminium trusses. The prefab frames are made of aluminium box profiles and flashings, with the wooden slats pre-assembled on them.

The shape and the dimensions of the facade (the centre-to-centre distance of the slats, for example) were chosen to optimize the sun shading capacities of the facade. The facade blocks the direct sun in the south, and opens up on the north facade for maximum daylight penetration. The wooden slats are labelled with an FSC and PEFC quality mark. Using structural calculations and simplifying the structure several times to work towards an efficient design, we were able to keep the amount of aluminium for the sub structure to a minimum.

Using BIM

The project was developed using BIM, which was a great help in particular with the finetuning of the mounting brackets on the underlying construction. The facade is mounted on various surfaces: on prefab wooden wall elements, on steel construction parts and on an aluminium curtain wall. Most of these building parts were designed and installed by other parties. By working in BIM, we were able to match the mullions in the prefab wooden wall elements to the grid of the facade and have mounting features Incorporated into the steel structure. Consoles were added to the curtain wall for mounting the trusses on that part of the facade.

Tekla Structures

Because the facade undulates irregularly around the building, no element is the same. To guarantee the dimensions of all unique assemblies, we put a lot of effort in making smart links between parts using Tekla. This made it possible to find the exact locations for the cut mortise and tenon connections, and helped with designing the corners like puzzle pieces.

One of the most difficult details in the design is the mounting of the wooden slats on the aluminium frames. This coupling has a number of requirements: a slat is almost never parallel to the frame (there is always a small angular displacement) and the contact surface between the wood and the aluminium must be kept to a minimum. On top of all that: the centre-to-centre distance of the slats varies with the orientation of the facade. In order to meet these requirements in a single coupling, we chose to use a laser-cut comb-shaped plate as the connecting element. This plate reduces the contact surface between wood and aluminium and allows an angular rotation. It also fixes the position of the wooden slat onto the aluminium substructure. Using these comb-shaped plates simplified the assembly of the slats significantly, since all the complexity is incorporated within this one element.

Grasshopper + Tekla = slim aluminium

We maximized the use of the Grasshopper – Tekla combination to capture the complexity of the design in the machine-produced parts. Doing so, we were able to guarantee the control of the dimensions and the manufacturability of this complex 3D facade. Working together in BIM with colleagues that supplied other parts of the building, we were able to find a continuous form and functionality for this capricious building envelope, using a slim aluminium frame. We are confident that Zuidwolde will be adorned with a striking Metadecor facade for many years to come!