Green roof: The most important information

Do you want to green your garage or carport? Here we have put together the most important information for you about different system solutions for green roofs as well as their advantages and requirements. We also give tips on creating and maintaining the green roof - because it is not just an optical renovation, but also has a lot to offer from an ecological perspective.

Table of contents Table of contents Green roofs: tips for planting and maintenance

• Advantages of green roofs
• Building a green roof
• Two types of green roofs: intensive and extensive
• Make the green roof yourself
• Cost and promotion of green roofs
• Expert interview: green roofs, good climate

Table of contents Table of contents Green roofs: tips for planting and maintenance

• Advantages of green roofs
• Building a green roof
• Two types of green roofs: intensive and extensive
• Make the green roof yourself
• Cost and promotion of green roofs
• Expert interview: green roofs, good climate

Advantages of green roofs

Clearly, green roofs are an important aspect of ecological building. Because: With the green roof, you ensure a better climate in your living environment. The green roof converts harmful carbon dioxide into oxygen and annually binds 0.2 kg of dust and pollutants from the air per square meter. In addition, you give plants and animals new habitats and increase biodiversity. You can also save: One to two liters of heating oil and waste water costs every year, because you can use up to 90 percent of the rainwater with the green roof.

Green roofs can also extend the lifespan of a roof by up to 25 years, because the heat shields the sun and UV rays from the plants, thereby protecting the material. The sound reflection to the outside drops by three decibels, and to the inside the ambient noise is about eight decibels quieter.

Because of these advantages, many cities and municipalities provide financial incentives for green roofs: where the so-called split wastewater fee has been introduced, you pay less, the more infiltration area or the fewer sealed areas your own property has.

• increases biodiversity
• stores rainwater
• binds dust
• optimizes thermal insulation
• extends the life of the roof
• swallows the sound

Building a green roof

The green roof consists of different layers: The bottom layer, which lies directly on the roof, is usually made of plastic fleece and protects the roof cover against damage from sharp-edged stones and roots. There is a waterproof protective film and possibly an additional root protective film. The next layer consists of a storage mat with a drainage layer for water storage and drainage. A fleece placed on top prevents washed-out substrate particles from clogging the water drainage over time. Then comes the specially mixed substrate layer for green roofs: it is light and permeable and usually consists of lava slag, clay granulate or pumice mixed with humus. A special mix of sprouts and seeds is sown on this layer. It consists of plants such as Dachwurz and various types of Sedum that can easily cope with the poor living conditions on the green roof.

The splendor of flowers proves it: green roofs enhance residential areas and houses. Anyone who clears only 5 centimeters of gravel has shoveled around 100 kilograms per square meter to green. The example shows a simple intensive greening.

Photo: Zinco

Two types of green roofs: intensive and extensive

• Extensive green roofs mean that the green roofs are a maximum of 20 centimeters high and are equipped with drought-tolerant plants such as sedum and Dachwurz. The roof is accessible for maintenance or inspection. The extensive roof greening adds an additional weight of 40 to 150 kilograms per square meter to the roof.
• With the intensive green roof, the plants, such as perennials and ornamental grasses, are up to 40 centimeters high. Intensive green roofs start from 150 kilograms per square meter. Green roofs populated with very large plants, which can rather be described as full roof gardens, can load the roof with over 500 kilograms per square meter.

So you see: Whether you choose extensive or intensive green roofs depends not only on the preference for small or large plants, but also on the statics of the building. Have this checked by a construction expert before starting the system.

Intensive and extensive green roofs differ greatly in terms of structure and planting.

Photo: MSG

Make the green roof yourself

If you want to make extensive green roofing yourself, you need the following materials:

• Root protection film (should protrude about 5 to 10 cm on all roof sides)
• Protective fleece (overlapping 10 cm)
• Drainage plates (also 10 cm overlapping)
• Filter fleece (also 10 cm overlapping)
• Inspection shaft
• gravel
• Green roof substrate (6 to 8 cm high)
• plants
• Fall protection (from 3 m height regulation)

In our picture gallery we show you step-by-step instructions on how to proceed with the installation of extensive green roofs. Please pay attention to the regulations for fall protection: take particular care in the edge area, eliminate trip hazards and set up the ladder in a stable manner.

Start photo gallery

10 Show all Extensive green roofs

Sweep the roof surface thoroughly and then lay out the opti-green root protection film. The film protrudes beyond the edge, so that you can cut it off at the end and put it under the sheet edge.

Photo: optigreen

With a knife above the roof drain, cut an opening out of the root protection film so that the water can run off later.

Photo: optigreen

The protective fleece is laid out in sheets. Make sure that you let it overlap ten centimeters with each new track. Cut off the edges so that you can stick them under the sheet. The roof drain is also cut out in the fleece.

Photo: optigreen

The drainage plates are laid out with the drainage slots facing up. Also pay attention to an overlap of ten centimeters and the hole for the drain.

Photo: optigreen

The last layer is the filter fleece. The sheets should extend to the outer edge of the roof. When laying, make sure there is a ten centimeter overlap and a hole for the drain.

Photo: optigreen

Insert a control shaft into the previously cut drain holes and fasten it with screws. A plant-free strip with gravel should run around it, width approx. 35 to 50 cm.

Photo: optigreen

The roof surface is covered with gravel and a green roof substrate six to eight centimeters high. Then smooth the surfaces with a rake and cut off the filter fleece at the edge areas just above the gravel or substrate surface.

Photo: optigreen

Sow the Sedum sprouts and the rest of the seeds evenly.

Photo: optigreen

Water until the water drains from the roof drain. Remember to keep your roof constantly moist for a month!

Photo: optigreen

After a year, your green roof can look like this.

Photo: optigreen

Sedum, Dachwurz and Heidenelken as well as various low grass types in all conceivable mixtures are particularly suitable for extensive green roofs. These plants require little maintenance and, thanks to their thick, water-storing leaves, also tolerate drought - overall ideal for a green roof. The plants are sown in May / June or September / October as seeds or sprouts.

After the extensive green roofs have been planted, watering should take place four times a week in the first month - it is best to place a sprinkler on the roof surface. This supports the proper growth of the plants. Further maintenance of the green roof is easy: weed the weeds twice a year and remove especially woody seedlings regularly - especially birch trees and aspen trees often germinate in the substrate layer.

Greening	Intense Greening	Extensive Greening
Optics	wholesome Garden area	Simple Green roof
maintenance	high effort	low
Cost / sqm	50 to 150 euros	25 to 35 euros
irrigation	regularly	only at the beginning
Construction height	15 to 150 cm	6 to 20 cm
Weight	150 to 500 kg / sqm	60 to 150 kg / sqm
plants	Cinquefoil, Pasque flower, Lavender, evening primrose, Sedge, Day lily, possibly smaller ornamental trees in Planters	Dachwurz, Heather, Little hawkweed, Carthusian carnation, Stonecrop, Schillergras, Carpet sedum, Grape saxifrage

The intensive green roof has the advantage that more plants can thrive here because the layer of soil is higher than in the extensive variant. Ornamental grasses, perennials and herbs make this form of green roof an exceptional eye-catcher. Of course, it needs more care. As in the garden, you need to water regularly or install automatic irrigation, cut off faded leaves and keep weeds at bay.

Good to know: Due to the special requirements for the statics, the extensive planning and considerations for fall protection, intensive green roofs should not be created by the layperson, but should be in the hands of a specialist.

Start photo gallery

7 Show all Plants suitable for green roofs

The dyed chamomile blooms from June to autumn.

Photo: MSG / Martin Staffler

The felt hornwort spreads rapidly and therefore requires a lot of space.

Photo: MSG / Dieke van Dieken

The stems of the golden-haired aster are equipped with needle-like leaves. Thanks to their bushy growth, these bring structure to the bed.

Photo: MSG / Uwe Messer

The Dost is very easy to spread and attracts all kinds of insects with its "pizza scent".

Photo: MSG / Susann Hayn

The upholstered gypsophila is native to our mountains. The majority of the plants bloom white, but now and then rose-blooming types can also form.

Photo: MSG / Alexandra Ichters

The hot stonecrop blooms from June to August and spreads widely.

Photo: MSG / Bettina Rehm

The cypress spurge is also spreading very quickly. It blooms from April to June.

Photo: MSG / Heike Marquardt

Cost and promotion of green roofs

The cost of extensive roof greening without plants is between 20 and 40 euros per square meter - the intensive roof greening in its simplest form is about twice as expensive. In most municipalities, green roofs are subsidized with up to 20 euros per square meter or as a percentage, at around 25 to 100 percent of the costs. But be careful: green roofs, which were stipulated as a requirement in the building permit, are usually exempt from these subsidies depending on the municipality - but it does not cost anything to ask! Green roofs are also often recognized as unsealing measures and rewarded with cheaper sewage fees. Depending on the municipality, the savings can amount to up to 1 euro per square meter of roof area and year.

If you renovate an older building and create a green roof, you can receive government funding from KfW, because the green roof counts as a thermal insulation measure in the "Energy-efficient renovation" program. For individual measures, a loan of EUR 50, 000 or a repayment-free grant of ten percent of the costs (up to EUR 5, 000) is possible. In order to submit the application to KfW-Bank, an expert federal energy advisor must issue the necessary certificate. Submit this to KfW before the roof renovation begins.

Expert interview: green roofs, good climate

New gardens are being created on all possible areas between, on and on the houses. DAS HAUS asks Prof. Dipl.-Ing. Nicole Pfoser, one of the leading researchers in green building: is that just fashion - or can we bring nature back to our cities?

Architect and specialist for green building: Nicole Pfoser.

Photo: Thomas Ott

Prof. Dipl-Ing. Nicole Pfoser is an architect, interior designer and master of landscape architecture. She teaches as a visiting professor for sustainable design and construction in landscape architecture at the University of Economics and Environment in Nürtingen and does research at the Technical University of Darmstadt about green roofs and green facades and their effects on the climatic environment, energy consumption and quality of life.

THE HOUSE: Ms. Pfoser, why should we make our houses greener in the future?

One advantage is the effect as external sun protection: 30 percent of the radiation is reflected by plants. They can absorb half of the rest. The plants convert 20 to 40 percent of this absorbed energy into perspiration. This improves the microclimate and saves energy when cooling. Take a dark roof that heats up to 60 to 80 degrees Celsius in intense sunlight - if clouds or rain come, it quickly cools down by 30 to 60 degrees Celsius. That means pure stress for material and connections. The green roof significantly reduces this. Green roofs can thus achieve twice the lifespan of green roofs.

The roof terrace of the Karlsruhe Environmental Agency is an ecological eye-catcher.

Photo: FBB

How does greening help with cooling?

Plants cool their surroundings through photosynthesis and evaporation, which can be promoted by a clever choice of plants. The greening of the house protects against heat and saves cooling energy. A year-round and hardy greening of the building also reduces heat loss because it protects the facade from wind and rain. Then it doesn't cool down so much.

Are there any effects on noise?

Greening has a clear effect on the noise level in the area. I measured a reduction in street noise by 5 decibels on a Patrick Blanc wall myself in Paris. This significantly improves the quality of life on site.

What does greening do for our environment?

A 20 centimeter thick ivy plant can absorb 2.3 kilograms of carbon dioxide per square meter per year and thereby produces 1.7 kilograms of oxygen. Overgrowth with moss and lichen is also very effective because these fine dust not only bind like other plants, but also metabolize a large part of it. Most greening leads to a multiplication of local animal species. Local songbirds find a good food supply in the green. And to clear up an old prejudice: insects do not actually come from the plants into the home, but stay in the greenery because this corresponds much more to their natural living space than a living space.

Does a green wall also affect us humans?

Green is comfortable: Studies in schools, offices and hospitals prove that people who live in green surroundings are healthier and can concentrate better. People need nature around them and find it nice to watch the changing seasons.

A herb meadow turns the flat roof into a garden. The pavilions wear a simpler green hat - the extensive variant.

Photo: DDV

What are the different types of greening of buildings?

Let's start with the roof. The simplest roof greening is the extensive one, which does not require much maintenance. In the past, you simply applied a few centimeters of substrate and then sown or planted the same. Today you can also work very well with moss or sedum mats. These are pre-cultivated and can be rolled out easily, similar to a turf. Then a roof is immediately green. Intensive greening takes more effort: a thicker layer of substrate with drainage and regular maintenance and irrigation. It also does a lot more for the microclimate of the environment and has other ecological advantages.

What does green roof mean for the statics of the building?

The more substrate you apply and the bigger the plants become, the more stressful the static of a roof. You need a structural engineer who calculates this.

Can only a flat roof be planted?

No. Pitched roofs can also support plants. You then have to work with horizontal thrust thresholds that prevent the substrate from slipping - they are particularly important in the first few years when the substrate is not yet fully rooted in the plants. This is technically not a problem, and the transition to greening the walls is fluid.

One to two inspection rounds are necessary each year to remove foreign growth. This green roof stores around 41 liters of water per square meter. The example shows extensive greening.

Photo: Zinco

What technical solutions are there for green walls?

The least expensive is the facade greening. But you have to be careful when choosing a self-cleaner such as ivy or wild wine. Such plants are a decision for life: their adhesive organs keep on cleaning - practically forever. The façade should be free of cracks before the vegetation, otherwise there is construction damage in the medium term due to ingrowth in the wall. Ranker, winder / winder and spreading climber need climbing aids, depending on the type, horizontally, vertically or in a grid. Plant pots that can be placed on consoles or pergolas or attached to the wall in front of shelves are also practical. The plant grows on a horizontal surface as it is used to. You can also tilt special containers 90 degrees forward and hang them in front of the facade, with the plant side facing out. Plantable mats are also used as a facade. Such types of construction can already be fitted in the nursery. Then you have a green house ready to move in. All wall-mounted systems must be artificially irrigated and supplied with nutrients. A circulating irrigation system is economical.

Who builds such green walls?

There are specialized greening companies in Germany. Without such know-how, mistakes can be made quickly: it's about the right material, the right choice of plants, the cardinal direction, light, water and nutrient supply and the right substrate.

Does a green wall need a lot of maintenance?

Unfortunately, it is not the case that the caretaker service could do the same thing. At least for public buildings you need a long-term maintenance contract. A specialist should check once or twice a year to make sure that everything is in order. If, for example, the irrigation fails, the green wall will quickly no longer look good. Many systems are therefore monitored with moisture sensors that report problems immediately.