Green inverted roof for a rural-urban residential neighborhood

Just outside Hamburg, a metropolis with a population of almost two million, yet surrounded by nature: the impressive location is one of the benefits that favor the residential construction project Magnoliengärten Lohbrügge right from the start. But project developer Bonava has many more arguments. One of them is the natural charm that the new neighborhood radiates, with some 100 homes and another 150 rental apartments. Lots of green dominates the overall picture – including the extensive green flat roofs. The inverted roofs use high-performance insulation materials from Jackon, which combine many benefits: an especially slim design and long service life along with high energy-efficiency that sets new standards.

The first families will be able to move into their new Magnoliengärten home by mid-2018, and the prestigious residential construction project is scheduled for completion by 2019. Eleven three-to-four-story buildings in all, plenty of green space around each of the structures, convenient furnishings, right down to the underground parking facility: with green spaces of 59 to 102 square meters, the attractive condominiums offer a complete package. “With its some 40,000 residents, the location in the placid community of Lohbrügge just outside Hamburg combines seemingly paradoxical elements: nature and family-friendly country life together with the metropolis of Hamburg at your doorstep,” explains Mani Pentschew, qualified mechanical engineer and Head of Building Site Service at Jackon.

Inverted roof insulation meets energy efficiency requirements

Already during the initial idea phase, Bonava’s planners recognized that a green inverted roof would be the perfect solution in this case, enabling them to achieve a number of different project requirements. After all, along with facades and windows, the roof represents the decisive parameter in the planning of the energy-based building shell – both with regard to energy efficiency and in view of the increasing inner-city population density. The first goal is to achieve good modern energy efficiency with excellent U values, but without losing floorspace, and while maintaining a streamlined facade design the same time. Along with that, the extensive roof planting contributes to a healthy micro-climate in Hamburg's idyllic Lohbrügge district.

Whereas facade insulation often reaches its practical limits with regard to insulation layer thickness, the roof offers greater depth here in the true sense of the word. The inverted roof also permitted the Magnoliengärten project to comply with building requirements under Germany’s Energy Saving Ordinance (EnEV 2014) and the KfW 55 standard. Additional arguments such as the optimization of construction times further bolstered the case for the inverted roof. By late 2015, the residential construction project developers had already turned to Jackon with these requirements and found in JACKODUR Plus a thoroughly persuasive, high-performance solution. This insulation material represents Jackon’s perfectly tailored, high-performance solution for the inverted roof application. Its excellent insulation properties, with ʎ_D = 0.027 W/(m·K), enables planners to create sustainable and energy-efficient building designs. “Made of extruded polystyrene foam (XPS), these thermal insulation boards have a closed-cell structure that makes them insensitive to moisture and maintains their compressive strength and dimensional stability even under high loads,” adds Mani Pentschew. That’s how JACKODUR Plus boards enable low structural depths with high efficiency, save installation time with their rapid, single-layer configuration, and also save valuable resources.

Time-saving installation and durable protection

Installation as part of an inverted roof has proven particularly economical in view of time savings and long service life. In this case, it is an unvented flat roof where the thermal insulation – unlike with the conventional arrangement – lies on top of the roof membrane and is thereby exposed to the weather. One big advantage of this approach is that the insulation layer provides the membrane with effective and durable protection against mechanical damage, UV embrittlement and extreme temperature fluctuations. As an alternative to classic roofing sheets, waterproof concrete construction is also an option. This variant was selected for use here.

Green roofs offer other benefits as well: Filtration of air pollutants and mitigation of the radiant heat improve the overall climate situation. At the same time, they have a compensating effect on the water balance by retaining, storing and delaying the drainage of precipitation. And last but not least, they also provide enhanced sound insulation.

Low installation height – excellent insulation performance

Made of extruded polystyrene foam (XPS), highly efficient JACKODUR® Plus insulation material is doing a great job in Magnoliengärten. The project is using 320-mm-thick JACKODUR Plus together with JACKODUR filter layer WA. The outstanding lambda value of the material enables it to achieve high insulation efficiency and the required U value of 0.100 W/(m²K). As the residential buildings are successively completed, some 4,000 square meters of roof area will be insulated and then extensively planted. By comparison, other XPS insulation materials would necessitate a 400-mm-thick insulation layer to achieve the same efficiency – which corresponds to a considerable 320-m² increase in material volume. Or in other words, had it not been for JACKODUR Plus, four additional truckloads of insulation would have had to be delivered and installed. The high-performance material has eliminated the need for that.

Sustainable thermal protection, full coverage in top form

This project proves once again that high-quality inverted roofs are purple thanks to high-performance insulation materials from Jackon. With their pioneering energy efficiency, Magnoliengärten Lohbrügge will soon be a green jewel on the edge of Hamburg, treating its new residents to a family-friendly natural setting.

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