Almondia – Bautipps Die Bauherrenberatung

green roof

Green roofs offer immense creative and ecological potential . They beautify the cityscape and climate. But green roofs are not only possible in the classic way on the roof of a house: the green areas are robust and easy to care for – their area of application is hardly limited. In addition to your own home, you can beautify your carport, tree house or even dog house with green roofs – there are no limits to your imagination.

the essentials in brief

  • Not only does the environment benefit from green roofs: They form a protective layer for your roof and also serve as an insulating layer.
  • Extensive green roofs are particularly suitable for your home because they are easy to care for, robust, versatile and you can save on waste water disposal costs with this type of green roof.
  • Precise cost guide values for small areas are hardly possible. Basically, the acquisition costs for green roofs are rather expensive.

Green roofs – That’s why they are important

Three types of extensive green roofs

  • direct growth: Consists mainly of a polyculture of mosses and lichens, after a growth phase of one year approximately 60% coverage of the vegetation is reached.
  • Textile systems: Pre-cultivated moss mats that take root particularly quickly on the roof.
  • Textile substrate systems: A substrate layer made of storage fleece is located under an organic fiber mat. It increases moisture retention. With this type of extensive green roof you have the largest selection of plants.

Greening buildings can make an immense contribution to improving the cityscape. An increased proportion of green space not only ensures a better urban climate, but also forms a good alternative habitat for animals.
But there are advantages not only for the environment. As a builder, you also benefit from a green roof. On the one hand, the ecological protective coating extends the life of your roof and, on the other hand, it represents good thermal insulation , comparable to an 80mm thick insulation material.
In addition, the green space retains water, which makes urban drainage and the work of the sewage treatment plants easier – and also your wallet if fragmented waste water statutes apply in your city.

Extensive greening vs. intensive greening

There are two basic types of green roofs: extensive green roofs and intensive green roofs. Intensive greening is rather unsuitable for the classic home, as it is considered too complex for private homeowners, both in terms of construction and maintenance. Extensive greening, on the other hand, is based primarily on moss and grass planting. Very easy to care for, these hardy plants are carefully selected to withstand wind, drought and even frost. But although such high demands are placed on the plants, there are numerous design options for green roofs, depending on preference. For example, color preferences can be taken into account when choosing plants.

Subsidies for green roofs

In Germany there are no uniform funding guidelines for green roofs, because they depend on the city and municipality. Often, however, green roofs are specified as compensatory measures by the intervention-compensatory specifications of the Federal Nature Conservation Act according to §19.
If you live in a city where you pay split sewage fees – this is the case in about 75% of all German cities, and the trend is rising – you can save up to €1.00/m² by retaining rainwater with green roofs save green space. Financial support of up to €10.00/m² is also possible.

What requirements does the area for green roofs have to meet?

If you want to green an area, some conditions must be met:

  • The roof construction: It is necessary to take the additional weight into account when planning the statics. The weight is made up of the water-saturated condition of the entire green roof structure including vegetation. That is around 100kg/m² for a simple extensive green roof.
  • The roof pitch: The basic rule is: More is possible than you think. The roof pitch is only an insurmountable obstacle for the green roof in extreme cases. Even with a roof pitch of more than 15 degrees, the green carpet is still possible. Then, however, shear protection measures must be taken to prevent the green roof from slipping.
  • The root protection layer: A root protection layer is absolutely necessary so that your roof is not damaged. It must bear the seal of approval “Rootfest” according to FLL (Research Society for Landscape Development and Landscaping).

What can a green roof cost?

The acquisition costs vary greatly depending on:

  • Type of green roof: Simple mosses and grass plants are the cheapest, but offer little creative freedom.
  • Building data: Depending on the statics of the area to be greened, additional costs may arise from shear protection measures.
  • Total area: A larger area is cheaper on average.
  • Logistical aspects: Depending on the weather conditions, a more or less complex layer structure is required.

With a simple extensive green roof, plants and a protective layer cost from €30/m². There are also one-off costs for the professional construction of the protective layers. Although this may seem expensive at first, there are costs for green roofs, especially at the beginning – after the purchase you usually do not have to plan any further large expenses. There are also savings due to the additional thermal insulation and water retention.

Split (or split) sewage fee: In general, property owners have to bear the costs for dirt and rainwater that occurs on their property. These costs are made up of the disposal and purification of the water. In the case of a split or split waste water fee, the costs for waste water and rainwater are calculated separately.

Dirty water fee: Dirty water consists of, for example, toilet flushing, shower water and dishwashing. The fee for the dirty water corresponds to the amount of drinking water consumed.

Fee for rainwater: When it rains, the rainwater that cannot seep into the ground is fed into the sewage system. The fee for rainwater is based on the size and type of sealed areas that cover your property.

Whether there is a split wastewater fee or not is regulated by the local authorities in the Federal Republic. Separate fees already exist in around 75% of all German cities. They are to be introduced in many other cities.

Playground for green ideas –
Embellish carports and co. with green roofs

Basically, you can embellish all possible areas according to the principle of green roofs. The only mandatory requirement is a high level of structural stability and that the area is accessible. If these conditions are met, there are hardly any limits to creativity. For simpler areas, such as the flat roof of a carport, you can lend a hand and save yourself the costs of assembly.
You don’t have to limit yourself to the simple grass and moss plants. A bed of roses is just as conceivable as a small vegetable garden. You can easily set up a playground for small animals on the roof of your carport.
In this way, the otherwise bare area can be optimally used according to your own needs.

Autorin Sarah Völkl

Sarah Völkl hat Architektur studiert und ist seit Jahren das Gesicht von a better place. Mit ihren Videos ist sie bei YouTube vielen Personen schon länger bekannt. Sarah teilt Ihr Wissen jetzt auch bei den Bautipps von Almondia.

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