UN JARDIN SUR LES TOITS

Un jardin sur les toits is a  consulting agency  and creative studio providing original content and innovative concepts in botanical and environmental subjects, combining scientific research and  wellness improvement.
Our vocation is threefold - design combined with sustainable development and ecological initiatives.
We practice the language of plants to give a tangible form to our desire to rethink the use of urban rooftops or all kinds of dedicated spaces in or out the cities.
We have set ourselves the challenge to improve air quality through a series of innovative proposals related to botany and technical innovations.
Placing medicinal plant or algae in the urban environment has emerged from our desire to restore the major role of Nature upon environment and wellness.
Our priority is to study the mechanism of botany in a polluted environment and to provide tangible solutions to improve health by improving air quality.
The benefits of using plants and algae have now been established and surely confirmed: massive absorption of CO2 and fine particules, combined with the reconstitution of the ecological network.
Given our aim to pursue the experience further, we consider it is essential to create a research station to analyse the development of plants in the urban environment on-site.
Driven by the desire to create a genuine synergy between the different participants in the field, exchanges between researchers are programmed and educational tools developed.
This dream, which takes shape day after day, is born from the "un jardin sur les toits" group's passion for plants and more generally for botany.

NANTERRE - PLACE DE LA BOULE - FIRST PRICE WINNER OF THE INTERNATIONAL COMPETION "Réinventons la Métropole du Grand Paris"
The air bubble
Located near the future station of the Grand Paris Express Nanterre La Boule (line 15 West) and carried by OGIC, the project Bubble Air aims to constitute a new entrance to the historic center of Nanterre in support of a building on the Place de la Boule, with a waterfall plant.
Designed by Brenac & Gonzales and Caractère spécial / Mathieu Poitevin Architects, Un Jardin Sur Les Toits will be in charge of developing well-being for users, as well as the development of a spirulina farm, a garden of Medicinal plants, an Aromatherapy program and, more generally, all botanical innovations.

Technology and science, combined with natural resources, offer today multiple solutions to improve urban environment. Many possibilities exist to reduce pollution of air and water, to eliminate noises, odors and electromagnetic nuisances, to insure healthier food, and to offer healthy and relaxing environments (homes, hotels, offices and gyms) for living, working, and fitness activities. Our commitment is to help our customers to find the best solutions to their requirements, combining new technologies and natural sciences, and to establish new standards for a high quality of living and wellbeing.

There are many positive technical impacts on the realm of extensively planted terraces and roofs, they always seems to be positive:
Waterproof materials are protected fromUV rays and sunlight and have a longer life.
Indeed, the deterioration of waterproofing membranes is mainly due to heat and UV rays. They damage synthetic elastomers or the oil in elastomer bitumen which become fragile. The plant substrate block the UV rays which are responsible for 5% of the aging of waterproofing roof. It is therefore a protection against badweather. These effects combined prolong the life expectancy of the waterproof membrane by 30 to 50 years.
The building and their occupants are protected against thermal shocks (cold rain on a hot roof, alternation between day/night or sun/clouds) reducing mechanic constraints which cause cracks. Thanks to thermal inertia,green roofs have a temperature variation of up to 40%, permitting significant reductions in energy costs.Roof membrane exposed to the sun can reach a temperature of 65°C,whereas the same membrane covered with plants stays at a temperature of15 to 20°C. The roof temperature impacts on the building's indoor temperature, and therefore on the need for air-conditioning. A plant-covered roof with a substrate of lightearth also reduces heat loss in winter.
Plants and substrates are some of the best acoustic insulation, as they absorb sound waves, hence reducing ambient sound levels. A 12cm thick substrate reduces sound by up to 40dB - another worthy advantage for areas where planes fly over at a low-altitude.
Impact on landscape and environment
Carefully designed living roofs improve the aesthetic value of cities, and particularly industrial cities. They also add value to habitations which are integrated in the environment. If they are designed with this in mind, they can also contribute to the ecological network ( biological corridors, buffer zones, biological connection zones, substitutional habitats, ecological fords, etc).

Impact on health
The positive impact on health does not seem to have been (yet) scientifically measured , but certain indices indicate that it is indisputable. Additional vegetation on roofs produces additional oxygen for cities. The plants and substrates fix and filter many atmospheric pollutants, such as sulphur dioxide and nitrogen oxide; micro, and perhaps even nano particles. Plants, in particular due to dew, retain dust and allergic pollen,and reduce the quantity of particles suspended in the air. An example of this effect is the use by different scientific programmes of moss to analyse the cartography of air pollution, given their capacity to capture and fix even heavy metals.

Social Impact
Living or green roofs make a built-up environment more "calm", less stressful. Inhabitants and users rediscover a harmony between urban life and a natural environment.

Economic impact (costs/benefits)
With regard to financial aspects, the CSTB (Centre scientifique et technique du bâtiment), has estimated the following average cost: a garden terrace on the surfacearea, the slope, the selected plants,and eventual necessary reinforcement of the structure, an additional cost of the waterproofness makes this solution less expensive than a tiled or slate roof.
It is difficult to evaluate in financial terms the environmental advantages for man, as well as certain additional positive effects: for health, reduction in energy use, increase in life expectancy of the structure etc.
The substrate and plants provide additional isolation (mainly againstheat). Temperatures under the roofs fluctuate moderately, reducing heating and cooling (air-conditioning in summer) costs for living or circulation. Living roofs also reduce certain individual and shared costs: health,water resource management, cleaning for which the dust, due to the quantity and relative toxicity, begins to create problems for elimination and storage. Maintenance and repair costs due to flooding, pollution created by sudden rising waters caused by saturated ground, malfunction in grainwater networks, water-treatmentplants, etc. are reduced when plant life is increased on saturated surfaces.
A rooftop garden also provides an additional living space for occupants,adding value to property for rent or sale in an urban environment. A living rooftop terrace also adds prestige to an office building for the companies who have access to it, adding a social and environmental engagement to any company sustainable policy.

TECHNICAL SCHEME

The primordial atmosphere
Today, our atmosphere is composed of about 21% of oxygen, 78% of nitrogen, and 1% of small quantities of various gases: argon, neon, hydrogen, etc. But it has not always been so! It is estimated that Earth's primordial atmosphere - about 4.5 billion years ago - was mostly composed of hydrogen, nitrogen, carbon dioxide (CO2), ammonia (NH3) and methane (CH4). No oxygen, therefore! Or in very small quantities, of the order of only 0.0001%.
Therefore, we are talking about the absence of O2 gas , at that time.  Paradoxically, the oxygen atoms were  all there, and they were  even among  the most abundant elements on earth. But for the most part they were linked to carbon to form CO2 or trapped in rocks of the crust and mantle.

All this changed with the appearance of life about 3.5 billion years ago. A key element of life as we know it, is the ability to produce organic carbon molecules (such as carbohydrates, proteins or lipids), which serve as sources of energy. To make them, living organisms have to find carbon. The first bacteria found their carbon by picking up what came within their reach as nutrients (humans do the same). But about 2.7 billion years ago, a new type of bacteria appeared: cyanobacteria.

Cyanobacteria were the first to invent photosynthesis as we know it. From CO2, water and solar energy, these bacteria - sometimes also called blue-green algae - were able to capture the carbon in the CO2, while rejecting oxygen! Unlike plants (which convert mineral nitrogen into organic nitrogen) and animals (which convert organic nitrogen into another organic nitrogen), cyanobacteria (and a few others) are able to take nitrogen directly into the air, gaseous form, and turn it into organic nitrogen. They thus put 100 million tons of mineral nitrogen a year at the disposal of plants on the planet.
Cyanobacteria, which make up a good part of phytoplankton, contribute significantly to the surface fixation of oceans, atmospheric carbon dioxide (CO2). This role is of major importance today because of the increased production of this greenhouse gas by human activities.
As an essential link in oceanic food chain, they contribute greatly to the transformation of CO2 into carbon (the organic pump) and its storage in deep ocean sediments (carbon sinks), in reserve for the future needs of the planet.

Air Composition
Dioxygen, O2: 20.9476%
Nitrogen, N2: 78.084%
Argon, Ar: 0.934%
Carbon dioxide, CO2: 0.0314%
Hydrogen, H2: 0.000 05%
Neon, Ne: 0.001 818%
Helium, He: 0.000 524%
Krypton, Kr: 0, 000 114%
Xenon, Xe: 0.000 008 7%


The measurement of oxygen content in inhaled air is fundamental to health, (as well as we measure the various primary pollutants: oxides of carbon, sulfur, nitrogen, VOCs, PM10 and PM2.5 particles , metals or light hydrocarbons and ozone), the constant must be 21%.

The combined action of land and oceans on atmospheric oxygen
Photosynthesis, respiration and dissolution in seawater act simultaneously and vary the concentration of oxygen in the atmosphere. These variations were measured by Keeling and Shertz (1992) in three places on the planet: Alaska, California and Tasmania. In the first two, both located in the northern hemisphere, there is a maximum of atmospheric oxygen in summer and a minimum in winter. The summer maximum is mainly due to the photosynthesis on the land surface that characterize this hemisphere. In winter, breathing and dissolving in the colder sea water combine to give rise to a minimum. Between maximum and minimum, the difference is approximately 26 ppm (parts per million) in Alaska, and 20 ppm in California. This difference is smaller in Tasmania (18 ppm), the southern hemisphere being mainly occupied by the oceans and terrestrial photosynthesis only plays a small role. These seasonal variations are very small compared to the oxygen concentration of about 200,000 ppm. The highest, that observed in Alaska, represents only 0.013%. Even a small change in the oceans balance , or global photosynthesis (even in the case of the Amazon, the so-called "lung of the planet"), could threaten the quality of the atmosphere in the medium term.

Human disturbance

For more than a century, man has been meeting his energy needs by burning coal and hydrocarbons from photosynthesis of past geological eras. This combustion consumes oxygen. Similarly, the increase in the world's population has led to the clearing of forests and replacing them with crops. This practice also results in oxygen consumption. On one hand, the biomass that constitutes the forest, very high, is largely transformed into carbon dioxide. On the other hand, agricultural practices generate an impoverishment of the soil by degradation of the organic material they contain (humus). This degradation is caused by organisms that breathe and therefore consume oxygen. The corresponding decreases are in total at the rate of about 4 ppm / year or about 0.002% of the oxygen content of the atmosphere.
Again, there are reasons to fear a lack in the decades to come, as the emissions of carbon dioxide by the man continue to increase every year .

Oxygen tends to associate with other chemicals to oxidize (burn). Thus, stocks of carbon or organic matter that do not currently participate in the living matter cycle could "go up in smoke" by incorporating oxygen. Soil organic matter is an example as we saw above when forests are cultivated. Oxidizable carbon stocks are available in the Geneva based 5th IPCC ( Intergovernmental Panel on Climate Change )report. Knowing that an oxidized carbon atom in a carbon dioxide molecule consumes an oxygen molecule, a rapid calculation gives, in case of rapid global oxidation of these stocks, the following orders of magnitude (percentages of decrease in atmospheric oxygen):
oxidation of hydrocarbons (gas) - 0,19% oxidation of hydrocarbons (petroleum) - 0,07% oxidation of coal - 0,16% oxidation of organic matter of soils - 0,64% oxidation of permafrost - 0,55%
Oil, gas and hydrocarbons, if they pose a threat to the climate, can therefore cause, in the case of intensive mining, a decrease in the oxygen concentration of the atmosphere.

According to a study of the INRS "National institute of research and security" on Confined Spaces, the measurement in oxygen content in a confined or polluted space must be controlled: Measure Oxygen Content Together, the oxygen content of the ambient atmosphere will be monitored using a portable oxygen meter. If the oxygen content is less than 19%, penetration should only be carried out with respiratory protective equipment. It should be noted that any measured oxygen concentration below 20.5% already reflects
an anomaly in the atmosphere of the confined space (oxygen consumption or accumulation of another gas).