Green roofs: plant, care and costs


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Green roofing is more than just an eco-friendly covering: The plants on the roof clean the air, as they filter out dust and air pollutants. The substrate stores rainwater and relieves the drainage system. In winter, green roofs act like a second insulating skin and help save heating energy. In the summer they keep the rooms below cooler. And: The plant carpet provides habitat for insects or ground-breeding birds.

Green roofs from extensive to intensive

Extensive green roofs are systems that are 6 to 20 centimeters high and are planted with sturdy, low-growing perennials such as stonecrop and houseleek. They are walkable for occasional control and care. With intensive green roofs, structures between 12 and 40 centimeters in height enable larger ornamental grasses, perennials, shrubs and small trees to grow here. Before deciding on green roofs, it is necessary to clarify the static load-bearing capacity of the building with the architect or property developer. An extensive roof greening brings about 40-150 kilograms per square meter of additional weight. Intensive green areas start at 150 kilograms and can load the roof with large planters for trees selectively with over 500 kilograms.

Extensive Dachbegruenung

Construction of an extensive green roof (Zinco system)

Building a green roof

Every green roof consists of several layers. At the bottom, a layer of fleece separates the existing roof from the new construction. A waterproof protective film with a 20-year durability guarantee is laid over it, and optionally a root protection film. This is followed by a storage mat in combination with a drainage layer. It serves on the one hand to store water, on the other hand to dissipate excess rainwater. A fleece as a fine-pored filter prevents eroded substrate particles from clogging the drainage over time.

The specially mixed, unfertilized substrate for green roofs is light and permeable. Airy materials such as lava, pumice or brick chippings provide for optimal ventilation and drainage, the humus content is only 10 to 15 percent.

Step by step: How to create an extensive roof greening

Lay root layer foil on roof

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Green roofs: plant, care and costs: care

Green roofs: plant, care and costs: green

Green roofs: plant, care and costs: roofs

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Green roofs

Green roofs: plant, care and costs: plant

The roof area is initially turned away thoroughly. Especially sharp-edged stones must be removed. Then lay out the root protection foil. You let them easily protrude over the edge and cut them at the end so that you can put them under the sheet edge

Green roofs: plant, care and costs: roof

Cut a round hole in the root protection foil over the roof drain with the utility knife

Green roofs: plant, care and costs: roofs

The protective fleece is laid in rows from a roof side with ten centimeters of overlap. Cut it at the edge to the size of the foil and also put it under the plate edge. The process is also cut free

Green roofs: plant, care and costs: care

The drainage mats resemble an egg pallet in their profile. They are designed with the drainage slits facing upwards and a few centimeters overlapping. Cut a suitable hole over the roof drain here as well

Green roofs: plant, care and costs: care

The last layer is a filter fleece. It prevents substrate particles from clogging the drainage. The lanes should overlap ten centimeters and reach the edge of the outer edge of the roof. The procedure is also cut free here

Green roofs: plant, care and costs: plant

Now place the plastic inspection shaft on the roof drain and pour it with a little gravel so that it does not shift. He will later be closed with a plastic lid

Green roofs: plant, care and costs: plant

Along the edge you first bring up a strip of gravel. The remaining area is covered with a six to eight centimeter high layer green roofing substrate. You level them with the back of the calculator. Thereafter, the filter fleece is cut off just above the gravel edge strip

Green roofs: plant, care and costs: costs

Distribute the sedum sprouts on the substrate and then sow the seed mixed with dry sand evenly

Green roofs: plant, care and costs: roof

Watering is continued until the substrate is well moistened and the water flows back through the roof drain. The new green roof must then be kept moist for three weeks

Green roofs: plant, care and costs: roofs

After a year, the extensive vegetation has already developed abundantly. After the growth phase, watering is only carried out if the drought persists

Lay root layer foil on roof

Cut hole in protective foil

Lay protective fleece in tracks

Lay out drainage mats

Lay out filter fleece

Put the inspection shaft on the roof outlet

Apply roof greening substrate

Sow seed on roof

Moisten the substrate

finished roof greening

Suitable plants for green roofs

For extensive green roofs so-called Sedum mixtures have proven. This refers to water-storing plants such as stonecrop (Sedum), houseleek (Sempervivum) or saxifrage (Saxifraga). The simplest method is to scatter short shoots of these plants as clippings on the ground (sprout mixtures). The best time for this are the months of May, June and September, October.Alternatives include flat-bales: plants that are grown and planted in very shallow vessels.

The higher the structure of the earth, the more plants thrive on the roof. From a 15 cm thick layer of soil complement ornamental grasses such as fescue (Festuca), sedge (Carex) or whitetip (Briza), as well as frugal perennials such as Pasque (Pulsatilla), Silberwurz (Dryas) or cinquefoil (Potentilla) and heat-compatible herbs such as sage, Thyme and lavender. In the following picture gallery we present you some selected plants.

Dyer Camomile (Anthemis tinctoria)

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Green roofs: plant, care and costs: roof

Green roofs: plant, care and costs: plant

Green roofs: plant, care and costs: roof

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Plants for green roofs (7)

Green roofs: plant, care and costs: roofs

The Dyer Chamomile (Anthemis tinctoria) is a native pioneer plant. It is a true perennial bloomer: from June until late autumn, the pretty wild plant produces countless golden yellow flowers

Green roofs: plant, care and costs: green

The felty hornwort (Cerastium tomentosum) forms silver-white upholstery with white flowers. It spreads quickly and therefore requires a lot of space

Green roofs: plant, care and costs: green

The golden-haired aster (Aster linosyris) bears on its unbranched stems yellow heads in a dense cluster. Pretty are the stems with needle-like leaves

Green roofs: plant, care and costs: green

The very prolific Dost (Origanum vulgare) attracts with its beautiful flowers not only all eyes, also butterflies and other insects fly on the old medicinal and aromatic plant

Green roofs: plant, care and costs: care

The cushion gypsophila (Gypsophila repens) is native to our latitudes. In summer, the creeping perennial impresses with numerous small white flowers

Green roofs: plant, care and costs: roofs

From June to August, the native stonecrop (Sedum acre) native of us produces bright yellow star-shaped flowers over the small, cylindrical shoots. He also spreads strong sometimes

Green roofs: plant, care and costs: care

The intensely lemon-yellow flowers of the cypress spurge (Euphorbia cyparissias) are hard to miss. Their bracts are often discolored red. The plant spreads over foothills extremely fast and strong

Dyer Camomile (Anthemis tinctoria)

Felt hornwort (Cerastium tomentosum)

Golden-haired aster (Aster linosyris)

 Dost (Origanum vulgare)

Upholstery Gypsophila (Gypsophila repens)

Spicy stonecrop (Sedum acre)

Cypress spurge (Euphorbia cyparissias)

Care of green roofs

In the first four weeks after planting, watering should be done up to four times a week to encourage growth. After that, the care is limited to one to two weeding sessions per year. Above all, tree seeds, for example birch trees, must always be removed regularly, so that their roots do not grow into the drainage layer.

Costs and funding programs

The cost of a roof greening are very different: The pure material value without plants is for the extensive roof greening of a garage roof in-house about 20-40 euros per square meter. Intense greening is about twice as expensive. However, many municipalities grant subsidies of 10 to 20 euros per square meter of green roof space or take on a percentage of the costs. Anyone renovating older buildings and using green roofs can take advantage of various subsidy programs - for example from the field of "modernizing living space" - which offer favorable financing through the Kreditanstalt für Wiederaufbau (KfW). Many municipalities also offer savings by recognizing green roofs as unsealing measures and rewarding them with cheaper wastewater charges.

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