Green roof — benefits, systems, technology

Green roof is a perfect solution for those who live in a big city, where there is a lack of fresh air and greenery.

Considering that visit to the park requires much time, so a small neat garden on the roof can be a nice opportunity to stay close to nature. Particularly, if you are a very busy person.

Green roof gives a full freedom for imagination. Design of the roof involves the use of different small architecture elements and floral elements. For example, it can be trellis, lattice, decorative walls and small groups of bushes.

Benefits

Private gardens on the roof are very popular and this is not surprising, it gives a lot of advantages, among them:

  • Natural evaporation of moisture allows to reduce spending on the cooling of buildings;
  • Allows to reduce the noise by absorption;
  • Can serve as an effective space for agriculture;
  • Green roof can increase the lifespan of roofing, because climatic and weather conditions don’t have such a strong impact on it;
  • Increase the value of the property;
  • Green roof allows to reduce spending on the heating of building, because it has great thermal insulation layer.
Green roof on skyscraper
Green roof on skyscraper

In addition to these benefits, green roof can give a nice aesthetic look for every building. For inhabitants of big cities such design of roof can give indispensible relaxing feelings and positive emotions.

Systems

There are two main types of green roof systems:

  • Extensive green roof;
  • Intensive (with special requirements).
Extensive roof irrigation
Extensive roof irrigation

Also some experts allocate following additional types:

  • Semi-intensive – 100-200 mm of substrate, wider range of plants;
  • Green roof with high biodiversity – supports particular species of plants;
  • Super lightweight – includes thin layer of drainage system (12 mm), vegetative layer (25 mm) and minimal loadings.

Of course, this list is not comprehensive and you can meet definition, which will combine two or even more types of green roof, listed above.

Selection of the concrete green roof system depends on the volume of soil and the degree of care. Planting of tall plants requires more soil (usually, it must reach about 1 meter). Constant care of growers are also needed in this case. Therefore, this type of gardening is named the intensive.

As a result, with this green roof system your roof will look like a real park, where you can cultivate almost any type of plants. It can be salads, trees or just bushes.

And in contrast, extensive green roof almost don’t need care and big layer of soil. You can fertilize the soil only once a year and it will be enough to maintain plant life. This type is really suitable, when it is impossible to ensure a large layer of soil on the roof.

It is need to stress, that extensive green roof is a perfect variant for buildings which were constructed long time ago. This type don’t need to be designed from the beginning of construction. It has light weight, unlike the intensive type which has large weight and requires serious maintenance.

On the other hand, intensive green roof allows to place a large flowerbeds, shrubs, birdhouse, recreation areas and even swimming pools, in contrast with the extensive type. Therefore, this system will give you a full feeling that you are in a real park.

Design

Green roof ensures wide freedom for the main design idea. You can decorate your roof in different styles, with the use of wide range of design constructions.

It is possible to equip green roof on residential houses with different architecture and even on garage. For example, on the roof with slope (more than 18 degrees) you should construct special framework fence, which will hold the planting material. It can be wires, frames or PVC grill.

Green roof on the roof with slope
Green roof on the roof with slope

Professional landscape designer can offer tracks, blocks of plants, small architectural forms, flowerbeds and other design options for your roof.

Storage for the equipment on the roof
Storage for the equipment on the roof

Also one of the most interesting ideas is the using of containers for plants. With this, you will be able to change planting design as you want.

Construction

Construction of green roof consists of following components:

  • Bottom layer – prevents the germination of roots. This layer is fitted directly on the hydro insulation layer to prevent its damage by the roots of plants;
  • Water-holding layer – ensures the additional protection of hydro insulation and also it is used as an accumulator of moisture;
  • Drainage system – regulates the outflow of moisture and accumulates the ideal amount of moisture which is necessary for the life of plants;
  • Filter layer – ensures the proper filtration of water, preventing the penetration of small particles of substrate to the drainage system;
  • Layer of soil – substrate, in which plants are planted;
  • Vegetative layer – lawn, small shrubs, perennial plants.

If you want to construct green roof you should pay particular attention to the contractor. You can join to the association or alliance of green roof fans. In such organisations people from all over the world share their examples of the successful execution of green roof design.

The installation of green roof
Photo: The installation of green roof

There you can find a lot of useful information about supplies, contractor companies and manufacturers (information about their products for green roof), which have passed strict certification.

Video: How to install a green roof.

It is recommended to use plastic frame with holes for rainwater as a bottom layers of green roof. Different materials, like membranes, ruberoid and mastic can be used for hydro insulation.

Detail

Green roof is a construction that can be completely installed on the place of assembly. Therefore the process of installation will be quick enough.

It is important to install special parapet with the height of at least 120 inches. This construction must be reliable and strong enough to withstand the weight of human.

In addition to this, for the additional security it is recommended to install special wind protection and strengthening.

Also you should to think about the organisation of additional facilities for the storage of equipment. Many facts show that all solutions should be planned on the design stage of green roof.

Technology

You should pay great attention to preparation of the green roof installation. Surface of the roof must be absolutely flat (for example, it can be flat panels), so shingles and tiles should be removed from the roof.

The structure of green roof has following layers:

  • Basis or slabs;
  • Membrane, which will protect the root system and avoids damage of the roof;
  • The next layer is geotextile material and vegetable pad;
  • Ground layer.

On the flat surface of roofing you must lay the bottom crate, then install boards with the thickness of 19 inches. After that you can put the layer of Styrofoam (this material is often used in industry now) with drainage pipes which must be wrapped with geotextile material.

Normal conditions for the effective plant life can be achieved only with the presence of three layers:

  • Draining layer;
  • Filter;
  • Soil.
Material for the filter layer
Material for the filter layer

Styrofoam tile is a perfect material for the arrangement of drainage system for green roof. You can use special equipment for leak detection on the stage of green roof construction.

Filter layer is made from artificial materials, such as foam, fiberglass, polypropylene.

The main task of substrate layer is to hold water for plants as long as it possible.

Plants

Selecting of plants for green roof is a quite difficult task, because you should consider many aspects and particulars of its design.

At the time of selection you should follow three criteria of plants for green roof:

  • Decorativeness;
  • Biocenosis;
  • Ecology

You should choose plants, which are not sensitive to the temperature differences or weather conditions changes. The best plants in this case are following:

  • Thyme;
  • Sage;
  • Periwinkle;
  • Lichen;
  • Lavender;
  • Crocuses;
  • Daffodils;
  • Moss
Thyme
Photo: Thyme

The ideal plant for the roofing plant carpet is sedum. This plant is not sensitive to the composition of the soil, amount of sunlight and also it offers a wide range of different shades.

Sedum green roofing carpet
Sedum green roofing carpet

The other option for roofing plant carpet is lawn. But it is need to stress that this type requires regular maintenance and attention.

Cost

Here you can see the average cost of the green roof installation in different US cities and Canada. It is need to stress that green roof needs considerable funding, the pricing is rather high.

City/State Cost per square foot, $
Boston/Massachusetts 30-35
Baltimore/Maryland 32-35
Chicago/Illinois 36-40
Tallahassee/Florida 30-33
Toronto/Ontario, Canada 30-35
Kansas City/Missouri 35-45
New-York/New-York 45-50
Ottawa/Ontario, Canada 28-35
Madison/Wisconsin 35-40
Yorkshire/New-York 35-38

Statistics show that green roof becomes more and more popular and in the nearest future this trend is expected to continue.


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