NACH
COURT BUILDING AMSTERDAM

A very grand and sizeable project with more than 3000 m2 of acoustic walls divided over 25 courtrooms.

What brought Alphenberg to the field of acoustic solutions?

After more than 10 years of experience in the field of leather applications in the interior, Alphenberg is well acquainted with the fact that leather has a softening and fire-retardant effect. But developing and making acoustic walls that meet the required values is something else. Yet, Alphenberg recognized the opportunities. And thus, within a year, a product was created that, according to us, has exceeded our expectations by far. It is obvious that process of developing a high-quality product does not always come easy. Complexity simply requires looking deeper research. And visual beauty, as a grand result, adds to the challenge.

NACH (New Amsterdam Court House)

In June 2019 we were approached to solve a problem that arose during the development of the construction of the NACH. The courthouse in Amsterdam on the Parnassusweg. The Borrenbergs company from Eersel, who are responsible for maintenance and supply of window decorations in the new courthouse, asked if we could handle an ambitious project. There were problems in all court rooms with the intended cladding of the walls. These walls, constructed in a technique that did not meet the obligatory fire safety standard, had not passed the required tests and were therefore rejected.

(For your information: For example, a single panel covered with fire-retardant materials can score a very good test result [indication fire class A], but the connection between the separate panels should also be accounted for. Something of paramount importance, particularly in this case, because of the enormous surface that needed to be covered. The outcome of the tests showed that the combination of three different materials (all of them with a fire class A qualification) only produced a class D or even E test result.)

The next logical question was whether we could provide a solution for this problem.

We were already working on the development of acoustic panels, but to be honest, the results were not yet sufficient for this project. The general atmosphere during the entire realization of the building project in Amsterdam, regardless of the complexity and the many, many requirements that we had to meet, fortunately left us enough time to develop the acoustic panels as the construction progressed. Inside the courthouse three converging worlds must, at all times, remain strictly separated: the judicature, the detainees and the visitors. Nevertheless, the ‘Rijksvastgoedbedrijf’ (Central Government Real Estate Agency) desired a transparent building, without the risk of compromising the safety of employees and visitors. This is exactly where good quality acoustics in courtrooms play a major role.

The starting points were clear to us

Would we be able to meet both the requested value for the fire class and the acoustics?
We started talking to KAAN architects from Rotterdam, KAAN is part of the NACH consortium and is a globally operating company, specialized in large-scale projects with an emphasis on functionality, which fits the NACH principle perfectly: ‘everything is intended to support the various functions.’
We proceeded to show various options, including our self-made perforated leather. We also showed a frame, somewhat reminiscent of a radiator, consisting of slats covered with leather. While fine-tuning the latter, the idea arose to make hemispheres on the slats as if they were halved broom handles. Eventually, this last option was chosen.

BROOM is the name, with a wink of course, but once you look at it you immediately understand why.

BROOM is the name we gave to this product, quite logically

With a wink of course, but when you look at it you immediately understand why. Broom consists of a fire-retardant MDF frame on which a firet-linen in the correct color is stretched. Subsequently, the leather-covered semi-circular slats are attached to this frame. And so the requested ton-sur-ton effect was achieved, creating an even more beautiful and serene look. The built-up also a includes a rock wool layer which greatly improves the absorption of sound and has a strong fire-retardant effect.

The next phase: testing

And we are happy to say that the result was above expectations. Contrary to the prediction of the acoustic consultant (Peutz), we achieved a result of alpha 0.70 instead of 0.45. During the test phase, we also developed a flexible system to measure the perfect distance between the leather bars, for even further optimization. Ultimately the fire test produced a fire class C qualification, which is, admittedly, insufficient for a hotel room, but it met the required standard for using it in the courthouse..

Quality comes with a price tag

The next step was placing the BROOM panels in the test chamber. This turned out to be slightly more complex than expected because despite the presumed standard dimensions, very little turned out to be standard. Instead of consistent dimensions, various elements such as doors, domotics and many of the spying-mirrors in doors induced an increasingly made-to-measure approach. The making a product turned out to be very complex and therefore time-consuming.