Artist Impression The Green House: CEPEZED


The Green House in Utrecht: How do you design a circular building?

We asked the architect Jaap Bosch

By: Jessica Merkens

Amidst the orderly chaos of Utrecht (The Netherlands) central station and the busy streets, pedestrians will find an unusual glass building: The Green House. The recently opened pavilion is a circular building.

What’s so special about The Green House and how do you build using circular building principles? We asked architect Jaap Bosch from Cepezed Architects.

What was the assignment?

“The Green House was part of the assignment we received for an adjacent state office building. This area will be constructed in three phases. In the first phase, the old barracks will be renovated into a state office and conference centre. We were asked to figure out how to make the area surrounding the barracks lively for the next fifteen years until the final phase of construction starts.

That’s how the idea arose to make a circular building that could be taken apart into pieces and rebuild somewhere else. The building has a café on the ground floor and conference rooms on the first floor. It’s located on a prominent intersection in the city, and in that sense, it seemed logical to add some liveliness on that location.”

How did you make the architectural design for The Green House?

“Actually, there were only a few conditions that needed to be met. It had to be somewhere between two hundred and three thousand square metres big and fit within the timeframe of phase three construction. That’s what made it a lot of fun, we were free to decide what we wanted to with the design.”

What do you have to take into account when constructing a sustainable circular building?

“First, it’s vital that you build something that can be taken apart. A classical foundation and ground floor with poured concrete is difficult to remove so we used prefabricated concrete blocks for the foundation. You also wouldn’t want to mason the walls or pour concrete walls. For the Green House, we chose for a steel frame with bolted joints so we could assemble it on-site.

We also had to figure something out for the façade. We again used the idea of using loose elements. Loose wooden parts form the facade, similar to what we did with the glass facade. We also tried to minimise the use of sealant for the glass façade.

Photo by: Lucas van der Wee, CEPEZED

Photo by: Lucas van der Wee, CEPEZED

Photo by: Lucas van der Wee, CEPEZED

Photo by: Lucas van der Wee, CEPEZED

Photo by: Lucas van der Wee, CEPEZED

Circularity means that you create something that can have a second life on a different location, but also that you try to use materials that are already there. We reused glass panels from the old barracks for the facade, and the floor consists of second-hand tiles and bricks. Even the furniture is mostly reused; the owner found most of it in thrift stores.”

What challenges did you face during the building process?

“It was a challenge to prefabricate all materials and without permanently attaching elements together. This was especially challenging for the contractor who was used to traditional constructing.

The building was designed in a way that all the installations such as air vents remained visible, so another challenge was to make sure that everything looked neatly from the outside. It was a real puzzle.”

What are you most proud of?

“Mostly that we were really able to simplify the building in a way that it is possible to dismount the structure after fifteen years completely. Also, that we were able to make real eyecatchers such as the façade from second-hand materials that might be discarded at first glance.”

The Urban Farm

“A vertical farm and outside garden with a surface of 90 squared metres deliver six tonnes of food for the restaurant of The Green House. Over sixty types of vegetables, fruits and herbs are grown. The discharged water is recycled, and organic waste that is coming from the kitchen is reused as compost for the Farm. Special UV lighting is installed above the plants to stimulate optimal growth.”

Do you have tips for architects who want to create a circular building?

“Step one is to look at the building as an assembly set instead of a traditional structure. Step two is to look around in the area to see what’s already there that you could reuse. Step three is to build something that uses a minimal amount of energy and strive towards the building becoming self-sufficient. Those are the most critical issues.

In the Green House electricity is supplied by solar panels. Cooking is done on barbecues and ovens that are heated by wood. Heat and air-conditioning are transferred from the nearby state office. For lighting, we came up with a pay-per-use model together with TRILUX where the manufacturer will supply light for the next fifteen years. A lot of materials often end in the trash when a building reaches the end of its lifecycle. With this model, this is avoided, since the manufacturer can dismantle the luminaires and reuse it somewhere else.”

What can visitors expect?

“A lively place, not just for commuters but also for the neighbourhood. You can have dinner on the surrounding terraces outside the building. The food will be sustainable, where the use of meat is minimised, and a greenhouse will supply the restaurant with homegrown vegetables and herbs.”

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Artist Impression The Green House: CEPEZED

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