Sustainable Garden Roofs Developed As New Construction Material
ScienceDaily (Nov. 30, 2008) A Spanish research study has tested
different combinations of supports and indigenous plants to determine
which are the best for reducing energy consumption inside buildings.
This type of roof is a rurban, sustainable architectural solution
that will lead to a reduction in environmental and acoustic
contamination levels in cities, and be visually pleasing.
Researchers from the Polytechnic University of Madrid (UPM) have built
a roof covered with plants and a watering system that will optimise
the consumption of a buildings heating and cooling systems thanks to
its insulation. It is a third-generation ecological roof,
characterised by its sustainability and the use of indigenous plant
The importance of the roofs, explained Francisco Javier Neila,
Professor at the UPM and co-author of the study, to SINC, is that
each geographical area requires the structures and plant species that
work best. In this case, the researchers divided the roof of an
experimental building in Colmenar Viejo (Madrid) into 20 modules, and
carried out a test with different supports and regional plants based
on three factors: the plant growing at a good speed, the density of
the biomass perfectly covering the roof and the result being visually
Indigenous species work better
In winter and summer conditions, the best performing roof has an 8 cm
tank that collects rainwater and offers an even irrigation system.
Plants such as sedum (Sedum praealtum) or aptenia (Aptenia cordifolia)
provide the best insulation because they have a thick leaf and are
resistant to frosts and heat, indicated Neila. But each location
where an ecological roof is installed will have its own catalogue of
plants, starting with indigenous plants because in its habitat, the
plant performs better.
The researchers also considered covering the roofs with an effective
plant and decorating it with another prettier one to fulfil both
requirements, but the result is difficult ,since when a single space
is shared by two species, the stronger one will predominate, Neila
There are a series of superimposed layers under the groundcover. The
first is a very light special substrate which helps to drain rainwater
quickly so the plant does not drown. Here, the best solution is pine
bark crushed and mixed with sewage sludge.
The substrate lies on porous concrete which acts as a sieve for excess
water that will end up in the tank, the capacity of which is
controlled by raised floor systems similar to those that support the
raised floor of an office. The water contained rises up to the roof
through capillary action and enables even irrigation. Just before the
buildings floor framing, the roof consists of a waterproof sheet
which prevents leaks.
Between each layer an extruded polystyrene sheet is inserted which,
according to the roof model, can be situated under the porous concrete
or beneath the tank. Each layer also includes a sensor that measures
temperature and humidity variables which can be compared with data
collected by an adjoining weather station for checking any change
caused by the roof during the four seasons of the year.
The researchers have also left various modules without an ecological
roof to clearly demonstrate its effectiveness. Roof areas with plants
optimise better the heating and cooling of a building than a normal
structure, regardless of how well insulated it is, the expert
commented to SINC.
The design of ecological roofs responds to the challenge of merging
urban and rural lifestyles and is being developed in countries such as
Germany, Switzerland, the USA and South Africa. Ecological roofs
reduce pollution in cities, absorb lead and other organic components.
A forest would be less contaminated with the same intensity of urban
pollution", said Neila.
These roofs will help to reduce the temperature of cities, which today
are a kind of urban heat island. Scientists have also estimated that
acoustic contamination would be reduced to three decibels, thanks to
Groundcover is therefore becoming a new type of building material but
development prospects are not positive due to its high price. Neila
cites Germany, where the situation is being resolved with tax
benefits, council taxes, increase in suitability for building, which
means it does not cost developers so much to invest in this option.
Adapted from materials provided by Plataforma SINC, via AlphaGalileo.
Email or share this story: Need to cite this story in your essay,
paper, or report? Plataforma SINC (2008, November 30). Sustainable
Garden Roofs Developed As New Construction Material. ScienceDaily.