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Tropical greenhouse for Cologne Botanical Gardens wins BTTV 2021
Tropical greenhouse for Cologne Botanical Gardens wins BTTV 2021
Tropical greenhouse for Cologne Botanical Gardens wins BTTV 2021
Tropical greenhouse for Cologne Botanical Gardens wins BTTV 2021

Tropical greenhouse for Cologne Botanical Gardens wins BTTV 2021

July 2021 - Hooray! On Thursday, 27 May 2021, the “Tropical Greenhouse for the Cologne Botanical Gardens” won the 2021 Benelux Trophy for Hot-Dip Galvanising in the “Functional Galvanising” category. Smiemans Projecten is the builder of the glass structure. Ferross Staalbouw delivered approximately 250 tons of steel and Rotocoat galvanised the steel.

Jury report

“The dimensions and shape of this greenhouse structure presented many technical challenges. The glass shell was mounted directly on the steel structure. To stop the glass breaking, no tolerances are possible in the galvanised steel. With large curved steel trusses, it was quite a job to get this done. In addition, a lot of attention was paid to the optimal layer thickness and the appearance of the zinc layer. In short: this is a very successful project from both a technical and an aesthetic point of view. It makes the most of the advantages of hot-dip galvanised steel”. 

Glass palace

The Flora und Botanischer Garten in Cologne was established in 1863 and it covers an area of 11.5 hectares.  It is one of the most famous botanical gardens in Germany and it welcomes more than a million visitors every year. 

In the middle of the gardens, a special glass structure with an area of 3,000 m2 is being built that reproduces the conditions of a tropical rainforest and a desert climate. 

Curved glass structure

Architect Königs has used no less than 4500 m2 of insulated glass in the design. A smart elliptical steel structure directly below the glass surface lets in as much sunlight as possible and shadows are kept to a minimum. 

In combination with special, extra translucent, insulating glass, this provides a lot of sunlight, heat and high humidity, which is essential for the native plants.

Unique steel body 

Ferross Staalbouw was responsible for the steel body of this unique project, which consists of a U-shape in which three curved greenhouses merge into each other. A total of 250 tons of steel were used. The profiles for the 80 curved trusses were produced specially for this project; they are IPEO profiles that are not available as standard on the market. 

The main building is approximately 22 metres wide and the truss is approximately 17 metres high, about the same as a six-floor apartment building. This means there is room for a walkway from which visitors can admire the tropical plants from a considerable height.

Rotocoat for enduring protection from corrosion

Because of the high humidity, the steel structure needs enduring protection from corrosion. That is why Rotocoat hot-dip galvanised the entire steel structure with a minimum guaranteed layer thickness in line with the specifications of Ferross Staalbouw.

The zinc alloy is hard, and wear- and chip-proof, and it can cope well with mechanical loads. If it does get damaged, a chemical reaction follows (cathodic protection), which means that properly galvanised products will not rust. Only galvanisation provides this unique protection.


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