In densely populated cities around the world, rooftop gardens and their cousin green roofs, are becoming increasingly popular. In The Bahamas, where we still have a lot of green spaces, this concept may seem a bit odd. But for persons living in high rise apartments and office buildings, growing plants on a rooftop makes a lot of sense. Green roofs are similar to rooftop gardens, but differ in that the former are not usually accessible.
The attributes of the green roof are rather extensive as a well-designed roof can insulate a building and extend the life of the roof membrane. They of course improve the aesthetics of the building, though you would need to be in a taller building to appreciate this. Among their other charms, they have been said to help reverse the hot island effect in dense urban areas and are able to deal with absorption of rainfall, the latter of which is negatively impacted in very built up cities, dubbed concrete jungles.
Some green roofs have even been transformed into wildlife habitats. As can be expected, they tend to result in a rise in property value for the owner. Rooftop gardens, which are very similar, have a long history and have been utilized as far back as the Babylonians and Romans at Pompeii. In recent decades, they have gained much popularity in Europe and are now increasingly seen in the U.S. These gardens are designed to be accessible to building occupants and become important recreational spaces for city dwellers who might otherwise not have access to a green space on their property.
Gardening is achieved by many means, including hydroponics and container gardening. In some instances, the area of the garden is increased by adding platforms called aero-bridges. These attractive gardens help owners to reduce their energy costs because plants will reduce the heat absorption of the building. Typically these buildings and surrounding parking lots absorb a lot of heat then radiate it back out.
At the roof level plants help to reduce this effect through transpiration thus minimizing the heat transferred to the building. It's easy for us here in The Bahamas to take what we have for granted. The fact is, most of us could simply step outside into lush gardens. We can pretty much plant whatever the soil would tolerate. Even if you have never worked or studied in a large city, most of us have felt the difference in heat effects when we land in south Florida, where extensive tracts of natural vegetation have been razed to make way for hotels, malls and parking lots.
Green roofs or roof gardens provide another opportunity to reduce the load on the cooling system of a building and may create a unique recreational space. The extent to which dwellers in large cities go to in order to duplicate what we have in abundance, serves as a reminder for us to be good stewards of our environment. o Send questions or comments to sbrown@graphitebahamas.com. Sonia Brown is principal of Graphite Engineering Ltd. and is a registered professional engineer.
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