A new envelope to bring the Municipal Civil Court of Zagreb to the 21st century
It rises in one of the main streets of the Croatian capital like a colossus. The Municipal Civil Court of Zagreb (Palača Pradve) bears little resemblance to the open-concept buildings being constructed nowadays. Instead, it resembles a massive metal framework, a shell in which dozens of employees of Croatia’s judicial system find shelter every day.
The building was erected in the early 1970s, under the direction of architect Ninoslav Kučan, who conceived the structure as a robust combination of lines and right angles. This seven-storey building with basement is divided in multiple courtrooms and offices, that rest upon a structure of columns clad in dark grey marble.
The materials used highlight the simplicity and purity of the structure, as well as the architectural principles of functionalism, which align with Kučan’s broader philosophy for architecture, who drafted the first plans of the building in 1961. The project was so well received by the city’s residents and cultural figures that, in 1970, it was awarded the Zagreb Salon of Architecture award.
However, half a century later, the insulation and functionality issues of the building envelope forced the Croatian government’s Cultural Heritage department to approve a complex renovation project. In order to carry out the renovation, the Large-scale Developments Engineering department and Alumont, Cortizo’s official installer in the Slavic country, designed a solution to restore the historical façade without altering its distinct aesthetic in the slightest or disrupting the activity inside the courthouse.
An engineering challenge with Cortizo’s signature
One of the first challenges faced by the team in charge of the renovation was the need to preserve its original appearance while meeting the current thermal performance requirements. For this reason, they proposed a new façade based on the TP-52 system. The new envelope, spanning over 8,500 m², needed to include specific adaptations to allow for the installation of wood on the inner profiles of the façade. Following this premise, a curtain wall was designed with a structure that combines Equity mullions and transoms, used to facilitate de installation of slats on the inner face, along with larger, bespoke profiles created specifically for the project. Due to the differences in how these materials behave with changes in temperature and humidity, an ad hoc coupling system had to be developed to counteract the variations in expansion and contraction of the wood and aluminium. Additionally, to replicate the external aesthetics envisioned by Kučan, a combination of glass, wired glass and stone was used, fixed to the supporting structure with pressure profiles covered by square caps (sightlines of 130 mm) and flat caps (52 mm). This way, the combination of vertical and horizontal lines gives the building the appearance of an enormous grid, a sort of giant game board, where the tokens are the sunrays reflected on the glass.
The renovation project of the curtain wall in the Municipal Civil Court of Zagreb posed a second challenge: the replacement of 1452 openings, whose thermal performance did not comply with current regulations, with new high-performance ones. With the goal of perfectly replicating the pre-existing windows, Cortizo’s engineers adapted the size of the sashes – 2.1 metres high and 1.2 metres wide – and kept the horizontal axis pivoting closing mechanism. To this end, a specific milling was performed in some of the frame slats, since one of the project’s requirements was the ability to entirely clean the systems from the inside. The team designed a bespoke solution based on the COR 70 Industrial series from Cortizo, which incorporated a thermal break, high-insulation foams, triple glazing and ABS space bars, which improved the building’s thermal efficiency. In terms of aesthetics, the windows had to be aluminium on the outside and wood on the inside, just like the façade. Therefore, special glazing beads were created to facilitate the assembly of both materials.
The implementation of these improvements was supported by a transmittance below 1.2 W/m²K, a reduced value taking into account the limited glazed surface of the structure and the thermal conductivity of materials such as stone. Thus, the more than 150 tons of anodised aluminium extruded by Cortizo were used to give the building’s envelope a second life. Its straight and bold lines will certainly continue to be the veins of Croatia’s judicial heart for many years.
Technical File
PROJECT: Municipal Civil Court of Zagreb (Palača Pravde)
LOCATION: Zagreb (Croacia)
ARCHITECT: Ninoslav Kučan
CORTIZO SYSTEMS: TP 52 façade adaptation and Cor 70 Industrial window system
INSTALLER: Alumont
Ninoslav Kučan
Ninoslav Kučan was born in 1927 in Breza, near Sarajevo (Bosnia and Herzegovina). After years of moving from city to city due to his father's work, and after losing his brother Mladen in World War II, he enrolled in a small fine arts academy. Later, in 1945, he started his architecture studies at the then Faculty of Engineering (Tehničkom fakultetu u Zagrebu), where he stood out in the Building and Design courses. He started his professional journey as an intern in the Urban Institute of the Republic of Croatia (Urbanističkom institutu NR Hrvatske).
In 1954, after serving in the military, he went back to university, this time as part of the Architecture Department of the Faculty of Engineering of Zagreb. Around a decade later, in 1967, he went to work in Germany, even though he returned to Croatia in 1969, where he continued his career. Finally, he passed away on the 22th August 1994 in Brač island (Croatia).