By Federico Bondone
Living ceilings or green roofs are spaces in which concrete or sheet metal surfaces have been replaced by spaces occupied by herbs. It is not the objective of this article to delve into the technical aspects of its construction, but to focus on the benefits they provide in terms of environmental services, the potential solution they provide to some problems and what are their advantages and potential when it comes to improving the urban habitat.
Green roofs or living roofs are roofs in which vegetation replaces conventional building materials. What are its advantages and potentialities when it comes to improving the urban habitat?
Living ceilings or green roofs are spaces in which concrete or sheet metal surfaces have been replaced by spaces occupied by herbs. It is not the objective of this article to delve into the technical aspects of their construction (for this purpose we recommend the book Green roofs. Execution, planning, practical advice, by Gernot Minke), but rather to focus on the benefits they provide in terms of environmental services and the potential solution they provide to some urban problems.
First of all, they are extremely energy efficient structures. A well-made living roof is practically imperishable and does not require additional care, thus avoiding the expense of money and supplies for its maintenance; once established, and if the correct plant species and a suitable substrate were used, it will not even need irrigation. Its insulating capacity avoids heat loss on cold days, making heating needs greatly reduced, and during hot times they keep spaces cool by preventing the sun's rays from directly impacting the building structure.
By retaining rainwater and slowly releasing fluids that exceed their capacity, they serve as relievers for the often collapsed storm drain systems, reducing the risks of flooding so frequent in some urban areas. On the other hand, they help in the control of ambient humidity by evaporating water on dry days and condensing dew on humid days, which can also help reduce the thermal amplitude. In addition to capturing moisture, herb leaves retain airborne dust and pollutant particles.
The so-called “heat island” effect (a phenomenon that occurs in cities, where the temperature is sometimes up to 10ºC higher than in neighboring rural areas, due to the absorption of heat by the asphalt during the day and its release gradual at night) could be markedly reduced with the addition of green roofs, by reducing the surface area of heat-absorbent materials exposed. For those who are in the City of Buenos Aires, they can put this phenomenon to the test by visiting the Faculty of Agronomy at night.
Since since the fixation of carbon dioxide (gas responsible for the greenhouse effect) and the release of oxygen is another of the benefits of these roofs, which should not be overlooked if we consider that most of the cities of the globe have a deficit of green spaces that compensate their emissions, and if we consider the energy waste involved in lawn maintenance (mowers, pesticides derived from oil, etc.), the few existing parks end up becoming sources of emissions. Living roofs, when not mowed, can accumulate much more carbon than a landscaping that is pruned regularly.
At the level of wildlife conservation, these roofs allow us to recreate degraded or disappeared environments (let's think of the practically extinct grasslands of the Argentine Pampean region, today replaced by monocultures, urbanizations and industrial parks), for which we must place special emphasis on the use of herbaceous plant species native to the region in which we live (which are also adapted to the rainfall regimes of the area); This will also benefit local wildlife, which will be able to find food, rest and shelter in areas that are now closed to them, as well as the possibility of creating green corridors that serve as communication between natural areas. In this way, birds and insects (particularly butterflies) would receive a necessary support during their migrations.
Although some authors do not recommend it, green roofs could be used for the development of urban agriculture, in particular for vegetable species with little root development and some aromatic herbs. However, we must not forget that living ceilings are just that: ceilings, and although they provide much more than a conventional concrete, tile or sheet ceiling, their main function is still merely structural.
Another advantage in terms of comfort, apart from how warm or cool they may be, has to do with its ability to isolate noise from outside.
Currently there are bills on the implementation of green roofs in Toronto (Canada), Mexico and Colombia, while some European countries do not have laws, but they do have regulations that establish some parameters that must be taken into account for guarantee building security, carried out by architecture colleges. Some of the laws seek to force construction companies to include a certain percentage of living roofs in each new construction, which has already put several companies on the defensive, either due to the increased cost of construction, or due to the known reluctance existing. to new paradigms and the comfort or distrust of academics in the building area.
Going to the concrete, the studies available so far indicate that it would take approximately one in five roofs in cities to be green, to bring pollution levels to desirable parameters. It will be a challenge for the authorities to learn to deal with these events, and it would be an extremely positive gesture to start with the landscaping of public administration buildings.
On an individual level, whoever can carry out this endeavor in their own home may be happy to know the good they are doing, and may be relieved to know that they no longer have to worry about leaks. Those who are part of a vertical property consortium can also delve into the subject and present a proposal to their neighbors, or at least generate expectations about the possibility of converting a terrace that nobody visits into a useful corner for nature and the urban environment.