The harvest from the roof

When Marcel Deravet takes us to the greenhouse in the first half of July, we are in for a surprise. Instead of basil and lollo rosso, there is a glaring emptiness on the almost 400 square metres. White containers, reminiscent of gutters, are lined up next to each other. Wiry strings hang above them, on which tomato bushes should actually shimmy up. As it turns out, the search for a new operator of the greenhouse was fraught with difficulties. But more about that later.

Fresh is a unique project by Luxembourg standards. With the Wolser industrial area, the greenhouse is located in an urban area. Moreover, the greenhouse is technically and architecturally integrated into a building.

With its half-lowered, shade-giving blinds, the greenhouse could probably blend in with the Kirchberg building landscape as an inconspicuous glazed office building. In reality, however, it is more reminiscent of the greenhouses widely used in the Netherlands. It is "a relatively light building", explains Marcel Deravet. The civil engineer is coordinating the Fresh project. Since the plants are grown in hydroponics, meaning that the nutrients are taken from the water and not from the soil, this corresponds to a load of about 40 kilograms per square metre, where otherwise it would be up to 900 kilograms, he says. "So you have something that is comparatively light, even compared to an existing roof". The pilot project is intended to help counter misconceptions that might be voiced by interested municipalities, for example. Because it has nothing to do with a fluttering foil tunnel on the roof of a building. "That's why we wanted a greenhouse that was aesthetically acceptable."