Green Roofs

Can they help you save money on energy?

Has it happened to you? After a long and hot day, you are ready to climb the stairs, enter your bedroom and rest. But then he remembers that he didn't turn on the air conditioning in advance and as it rises, an increasingly suffocating heat begins to overwhelm him. What a bummer! As always, the upstairs rooms are made of an oven and even if you turn on the air conditioning, you will end up with an incredibly high electricity bill. But did you know that the solution is right over your head? To be exact, on your roof. Did you know that a green roof could help you reduce more than 50% of your electricity consumption?

Green roofs are those that incorporate vegetation on the roofs of buildings and provide economic, social and environmental benefits. Let's take a closer look at these benefits.

ENERGY EFFICIENCY

Of the heat gain of a property, 70% comes from the roof due to its constant exposure to solar radiation. If your home has two levels, surely you can verify that the bedrooms on the upper floor are warmer than the ground floor. In part, this will depend on the construction system of the slab. For example, normally a concrete joist and vault slab will transmit 80% of the solar radiation received during the day to the interior. If the slab is made of polystyrene joist and box, it will transmit 70% and a solid concrete slab, 95% of heat. On the other hand, by adding a landscaped roof to its slab, it will only transmit 8%, achieving greater thermal comfort inside. This, in turn, reduces CO2 emissions and economic expense since a mechanical system is not necessary to cool the space, at least for most of the year. In fact, “it has been proven that the green roof can reduce energy demand by an average of 66 percent per year” (Zuleta, 2011).

RAIN WATER CONTROL

Green roofs are a good option to mitigate the impact of heavy rains on the city, since the water absorbed by the plants will be water that will not end up in the municipal drainage or in flooded streets. In addition, in a home it is possible to recover approximately 65% ​​of the absorbed water, treat it and use it for daily tasks such as washing, bathing and using the toilet.

OTHER BENEFITS

Having a green roof increases the value of the property and can be the ideal place to harvest vegetables for the family's consumption. In addition, although they could be considered islands in a concrete sea, they favor biodiversity in the city. Therefore, it would not be uncommon to receive a visit from birds, butterflies and other pollinators. Another important point is that with a square meter of green roof a kilo of CO2 is trapped and produces the necessary oxygen that a person needs in a year (Fundación UNAM, 2020). But in addition to the natural function of plants to provide oxygen, they trap and metabolize pollutants from industrial activity or vehicular traffic before they reach the atmosphere, turning them into beneficial molecules for plants.

The benefits of green roofs are not only for the property owner; they can also benefit the city. These significantly improve the urban image and, thanks to their natural evaporation and perspiration behavior, reduce the urban heat island effect, a phenomenon that is defined as the increase in the surface temperature of a city.

WHAT ABOUT THE COST AND MAINTENANCE?

Approximately, the installation of a green roof can cost about $ 400 pesos / m2 but you can be sure that the benefits of a green roof will outweigh the costs involved.

With regard to maintenance, this differs depending on the type of vegetation and the type of roof that is installed. However, it is possible to minimize the costs of this. For example, putting only 4 or 5 centimeters of soil before installing the roll grass. The less soil, the less food for the grass and the slower it will grow, therefore it can be cut only once every 30 days. On the other hand, a group of researchers from UNAM have proposed having a polyculture since plant diversity reduces the risk of pests and the use of agrochemicals and fertilizers is avoided. “Thus, roofs can be low maintenance; what's more, there may be zero maintenance. The viability of this environmental proposal has been reliably demonstrated in the Coordination of Scientific Research in Ciudad Universitaria, where since 2013 a garden that receives little maintenance has been established. " (López, 2019). Furthermore, it is suggested that all the plants to be selected be native or endemic to Mexico. And if they are local native plants, much better, because being adapted to our climate they require minimal maintenance.

As you can see, having a green roof offers you many benefits; to you, and to the city. Why not implement one in your home?