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Solar green roof

12 min read
Solar green roof

Landscaping a roof with vegetation, we can achieve significant benefits: beyond the positive effects on the environment, can help us to reduce costs regarding thermal insulation, soundproofing, the overload of drainage and sewage system, and the list could continue. It’s also recommended to combine extensive green roof systems with other ecological methods, for example installing solar panels.

Mounting photovoltaic panels on a green roof evidence even more that we have an ecological construction, but there are some practical aspects too: green energy is generated, the environment is protected and not least, the electricity bill is significantly reduced.

The cooling effect is also important – by the evaporation of moisture extracted by plants from the substrate – not only because of the reduction of ambient temperature of the building, but the surrounding atmosphere temperature too.

We must know that overheated solar panels lose their efficiency or they can even stop. So, installing them on roofs with green vegetation is more opportune; compared to traditional roofs, they are productive with 16% more.

Green roofs have anti-pollutant properties too: they capture micro particles and dust, so the environmental atmosphere becomes cleaner. Even photovoltaic panels remain spotless, so their maintenance is simple and they are able to absorb much energy.

Let’s not forget that mounting solar panels on the existing green roof, or landscape a green vegetation under the solar panels, involves several toilsome and delicate stages regarding the waterproofing or the links and connections between panels. So the best solution would be to landscape green roofs combined with the installation of photovoltaic panels, having lower costs and a uniform distribution of weight.

When the mounting of solar panels is integrated in the landscape of the multilayer extensive green roof system:
A protection layer, made of a membrane against root penetration (if the waterproofing doesn’t have FLL certification against root penetration)
Another protection layer, a geomembrane made of polyester fibres or mechanically consolidated fibres, with a water absorption rate of 3 and 6 l/m²,depending on the product
A network of drainage boards for retention, having the similar role to gravels, but with greater properties (gravel doesn’t have water retention capacity). They look like egg casings or some three-dimensional networks with holes for water retention, they are 20-30 mm high, retain water and direct excess water toward gutters. Depending on the model used, they can store 7-11,5 l of water per m², and their own weight is about 1,8-2 kg/m².

Parts of the panel support are especially designed for a quick installation, made of chemically compatible materials with the drainage boards. Panels of 1.000 mm, 1.200 mm can be installed and transversely, panels of 1.600 mm.
Photovoltaic panels. They have to be mounted in this stage in order to avoid the intense traffic later on. Assembling methods are established by the manufacturer, supporting elements are compatible with almost all type of models.
The next layer is a felt one for absorption and to distribute rainwater in order to irrigate areas under the panels.
Control boxes are also installed to observe condition of the inferior layers. Their adjustable height is up to 100 mm, with upper and side openings for drainage.
The vegetation substrate is spread to have a 60-200 mm thickness, depending on the climatic conditions and the type of vegetation. Being the place where roots live, it’s very important for their survival and development.

It is composed of recycled and natural materials, actually a mixture of granules of split face natural tiles, perlite, pumice, volcanic clay, peat and biodegradable fibres. The most important feature when choosing a certain substrate is its water retention capacity, which can vary between 25 and 40 % of the volume, and also the permeability and structural stability.
The vegetation layer: for extensive green roofs it’s recommended to use plants resistant to high temperature variations, extreme conditions, frost, drought, wind, acid rains etc. Sedum species, wild grasses are ideal for the role of vegetation on extensive green roofs, but they can also be combined with flowers and other plants. So we can achieve spectacular results, with high decorative value. There are known several planting and sewing methods, but the best solution is to use vegetation rolls. Working with these rolls, we can save money and time.

Sowing or dispersion of sedum seedlings/pieces is apparently a less expensive method, but the irrigation, maintenance until they reach maturity exceeds several time the cost of vegetation rolls. These rolls provide the coverage of 95% of the surface right after the installation, and they are immediately resistant to rainfalls. We cannot say that about the sowing method, because a heavy rainfall can compromise the whole plantation. Sedum rolls can rapidly root (10-14 days), have a three-dimensional structure and a fertile and well drained soil, so under normal circumstances after 1 year reach maturity. Once installed, they protect the entire stratification of the extensive green roof against harsh weather conditions.

Technical data of this structure in water saturated status:
Weight: 1-1,4 KN/m²
Thickness: de la 80 mm
Inclination: 0-5°
Vegetation: Sedum
Water retention: 50-60%
Discharging coefficient: 0 %: C = 0.17** 2–8 %: C ≤ 0.45
Water storage: 25 l/m²

An extensive green roof with solar panels is profitable, having reduced landscaping costs and a record time amortization of the investment. And of course we can have the opportunity to create our own terrace and a habitat with a special biodiversity. Photovoltaic panels and the surrounding vegetation protect a great variety of plants and animals against bad weather conditions.

We can offer consultancy to build green roofs and terraces, to install photovoltaic panels, bringing many benefits and positive effects on the environment. These solutions help maintaining the thermal comfort and soundproofing of the building and prevent the overload of the drainage and sewing systems.

Our team of experts is at your disposal with turnkey projects and long-term maintenance.
We use reliable building materials, plants especially developed for rooftop gardens and high quality vegetation rolls. Every landscape work offers the best cost/effectiveness/safety balance and every project is adapted to our customers’ aims.

We are able to landscape deck type green terraces with pedestrian traffic, intensive or extensive green roofs on the top of industrial halls, inside or outside vertical gardens for office buildings, and intensive green gardens with special relaxing zones, landscape green roofs with pedestrian traffic for shopping malls and many other ecological constructions.

To increase the ecological value of the building, solar panels can be also installed.
We are happy to help you with green projects, system solutions, estimates, and consultancy in the field.

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