Exemplary biodiverse green roof

Childcare Facility Grossenhain

Playing and learning in a friendly environment – that is precisely what the childcare facility in Grossenhain in Greater Dresden wants to offer in and with its new facility. The building provides the children and their childcare workers with lots of freedom, light and greenery. Even the extraordinary 880 m² roof is incorporated into the green area plan and is proving to be a blossoming eye-catcher for the entire neighbourhood. This richness of fauna and flora species is possible thanks to the ZinCo System Build-up “Irrigated Extensive Green Roof” with biodiverse modules. An exemplary green project – not only for the kiddies!

The City of Grossenhain is in the northeastern part of the state of Saxony and has a population of approx. 18,700. The childcare facility in Chladeniusstrasse has been in operation since the 1980s. However, the old three-storey building has now been replaced with an impressive new building and space for 111 children. It was designed by TSSB Architects in close collaboration with landscape architects Blaurock, both of which are based in Dresden.

The elongated, single-storey corner building follows the road line, while the courtyard and garden are protected at the rear of the site, which gets its lively silhouette from the six individual wood cabins that emerge from the building. These cabins are the group rooms, and each has a glass facade stretching from floor to gable, creating a close connection between indoors and outdoors. As these rooms face North, there is no need for a permanently closed sunshade and the view towards the greenery is available all day long. An additional advantage is that these rooms and their ancillary spaces such as sleeping rooms are at the rear of the building and are protected from street noise. The green roof provides sound insulation for the inner-lying rooms. It also has a temperature-balancing effect so that the rooms are cooler in the summer and warmer in the winter. There are additional benefits that favour the green roof: Protection of the building fabric, an extended service life of the roof, an improved micro-climate, water retention and its special contribution to the protection of biodiversity. Landscape architect, Claudia Blaurock emphasises the point: “The important thing for us was that the appearance of the new building and its outdoor areas would do justice to the childcare facility and would not resemble an architecture of institutions or office buildings that is easily duplicated. The intention is that pedagogic content is reflected in the building and the outdoor areas. This also includes aesthetic appreciation. The green roof with its biodiversity is an integral part of the cabin concept. People should have the feeling that they are standing in front of a rustic cabin. With the sand pockets and dead wood, we have also created a habitat for insects.”

Location factors

With an annual precipitation of only 550 – 600 mm, Grossenhain is in one of the driest regions in Germany. For this reason, the biodiverse green roof with the ZinCo System Build-up “Irrigated Extensive Green Roof” was chosen and installed. A feature of this roof is its efficient sub-surface irrigation system. The flat roof has a typical pitch of 2 % and is structurally designed to carry the weight of the green roof. A bituminous and root-resistant waterproofing provided the base for the start of the green roof works.

An ingenious system

The first layer in the ZinCo System Build-up “Irrigated Extensive Green Roof” is the Protection Mat SSM 45 which is followed by the drainage and water storage elements Floradrain® FD 25-E. These 25 mm high elements made of recycled polyolefin have troughs on the upper side to store water and a channel system on the underside for the safe drainage of excess water to the roof drains. This drainage layer is followed by the vapour permeable Aquafleece AF 300 and the dripperlines for sub-surface irrigation, which are attached to the Aquafleece with hook and loop tape strips at intervals of 50 cm. The special feature of the Aquafleece AF 300 is its two-layer build-up comprising an underlying dense fabric and an overlying fleece with a strong capillary action. Water coming from above (from rainfall or from the dripperlines) is firstly distributed horizontally across the entire fleece surface thanks to this capillary action. The water will only pass through the underlying fabric once the fleece is saturated. Due to this intelligent surface distribution, far fewer dripperlines are needed than is the case with conventional dripperline irrigation and the water is available in the root area without it disappearing as a result of evaporation. This is the great advantage of any sub-surface irrigation system compared with conventional irrigation from above, as is the case with a sprinkler system.  On the roof of the childcare facility the dripperlines are connected to a control element which automatically regulates irrigation in the absence of rainfall.

Wide variety of species

In order for the required variety of plants to become permanently established on the roof, both the water balance and an appropriately deep humus-rich substrate are relevant. In Grossenhain, therefore, the ZinCo System Substrate “Rockery Type Plants” has a depth of between 10 and 14 cm. Such mounding of the substrate depth allows for the specific design and planting of species that require greater root space. In this way, the inner areas on the roof of the childcare facility are overall deeper than for example is the case with the areas around the sand pockets and around all gravel strips at the roof edge, and around skylights and safety devices. Once the substrate was fully spread, the vegetation was added in the form of plants, cuttings and seeds.

In line with the planting plan, 5,000 pieces of 18 different perennials and grass types were initially planted which allowed for a quick surface coverage. In addition, the special seed mixture “Bee Pasture”, 7 kg of which was used, largely contributed to the impressive variety of species in the biodiverse green roof. The mixture contains more than 35 types of nectar-rich plants that bloom at different times. The flowering period begins as early as March with the spring cinquefoil and Caucasian rockcress and thanks to the mountain savory lasts into late autumn. Thus, the bees find nectar and pollen for as long as possible during the year. Finally, 12 kg of sedum cuttings were spread across the entire roof. These species are low growing and are therefore perfect for along the roof edges.

Bees, birds, butterflies and insects require not only a diversity of their forage plants on the roof but also hiding, breeding and sun spaces. Vegetation-free spaces such as the sand pockets and stacked dead wood are used for this. Dead branches are actually used as a habitat by moss, lichens, fungi, and beetles and other insects. These biodiverse modules can be created without much effort, and they convert the roof into a truly eco biotope with species-rich fauna and flora.

German Design Award 2024 Winner

The Grossenhain childcare facility won the German Design Award 2024 in the “Architecture” category. This is considered to be the most prestigious award in the international design sector and is awarded for pioneering projects. The City of Grossenhain and everyone involved in the project are proud to have created such an exemplary project with such charm and appeal.

Author: Dipl.-Wirt.-Ing. (FH) Sandra Schöll, Press Office, ZinCo GmbH

Site board

Construction project: Childcare Facility Chladeniusstrasse, 01558 Grossenhain, Germany

Construction year: 2022

Roof area: approx. 880 m²

Green roof build-up: ZinCo System Build-up “Irrigated Extensive Green Roof” with biodiverse modules

Client: City of Grossenhain, Germany

Architects: TSSB architekten, 01097 Dresden, Germany

Landscape architects: Blaurock Landschaftsarchitektur, 01099 Dresden, Germany

Waterproofing installation: Schelzel Bedachungs GmbH, 01157 Dresden

Green roof contractors: Heidel Garten- und Landschaftsbau, 08118 Hartenstein, Germany

System supplier: ZinCo GmbH, 72622 Nuertingen, Germany