Published 27/09/2017

Rooftop greenhouse to increase sustainability through awareness of local food production and promotion of local choices

Since 2016, tomatoes and cucumbers are grown in a greenhouse located on the rooftop of the former Philips building in The Hague, the Netherlands. The 1200m2 facility is the largest in Europe of its kind with the purpose to produce healthy food and to make consumers choose locally produced food. To achieve the climate needed two climate screens are installed – Svensson’s Harmony and Luxous.

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A local and sustainable food production

UrbanFarmers is the company behind the initiative of a city greenhouse in The Hague. “The roof of a building is often empty, which makes it an ideal space for a city greenhouse,” says Shuang Liu, Marketing Assistant at UrbanFarmers. “By developing greenhouses in the city, we can bring more food to consumers. We want to encourage people to buy, healthy and fresh food that has been produced only a few kilometres away from them, meaning that it is sustainable.”

Crops and fish provides healthy food

Tomatoes, cucumbers and lettuce are grown in the greenhouse. Total, there are 28 (large and small) tanks with fish - pink tilapia - on the ground floor. UrbanFarmers uses the aquaponics cultivation method, a closed system that combines fish farming and plant cultivation in a sustainable and efficient manner. In this system, the fish waste provides an organic food source for the plants, and the plants naturally filter the water for the fish. The nutrients that are released during fish farming are reused for the plants and the plants clean the water in which the fish are grown. Besides the production of local healthy and fresh food, UrbanFarmers has an educational goal: to raise awareness by showing people how vegetables are grown and food is cultivated. UrbanFarmers has established a strong ambition to create a movement where more and more consumers understand the importance of and opt for local food options.

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Challenges in building a high up, roof-top greenhouse

Greenhouse Builder, Van der Valk-Kleijn involved Steetec in the development of the roof-top greenhouse, as the installer had experience with building high greenhouses. “There is a huge difference between building a greenhouse on the ground versus on the top of a building,” explains Van Steekelenburg. “There is always wind when you’re 35 meters up in the air. To prevent damage to the climate screens, we have used a profile with plastic, wire-guided blocks both above and below the screen for extra protection. The profile is also heavier than usual so we attached a wire every 40 cm on the bottom and every 80 cm on the top. Finally, we have attached weights to the screens on the outside where they hang down, to prevent them from being blown upwards by the wind. The height forces you to think differently.”

Harmony and Luxous climate screens provide the climate needed

“A climate screen is used inside the roof-top greenhouse,” tells Hans van Steekelenburg, Co-Director of the installation company, Steetec. “The Harmony 3315 O FR was selected to provide the shade needed and more gentle, evenly spread light. We also installed a transparent Luxous façade screen that divides the greenhouse. Thanks to this dividing screen, a different climate can be created in the smaller section of the greenhouse, allowing the growth of lettuce which requires a different climate with more air and a different temperature. The dividing screen runs down vertically along the columns.”

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