Nashville’s Greening Looks Skyward

A green roof. What is it? How can it help offset global warming while increasing human comfort?

A green roof usually refers to a roof with something growing on it. If at least part of the roof is waterproofed, covered in a growing medium and planted with vegetation, then it is considered green. The designation refers more to the roof’s environmental impact than its color.

Recently, a Nashville law firm started work on their new green roof, and they are only one of a large handful of such projects. Nashville is home to a surprisingly large number of green roofs, notably the ATT tower and city hall’s Public Square. Nashville will be hosting a Green Roof Market Development Symposium in March which will undoubtedly increase the interest of this eco-friendly emerging market.

Green roofs often need special drainage or irrigation considerations. Ideally, they are self-sufficient, ie, not requiring a lot of maintenance. Container gardens may be considered green roofs, but only if there are enough planted containers that they cover a substantial portion of the roof. Generally speaking, containers have greater watering needs than larger, more exclusively green roofs. In completely green roofs, rainwater is filtered by green roofs, and some buildings have even found ways of incorporating this rainwater into their buildings system

One of the immediate advantages is that a green roof can be used as green-space by building users. It can be a place for vegetable or flower gardens for people living in a building, a place to enjoy for recreation, replacing individual patios. A green roof provides a somewhat more private space for people to enjoy, as opposed to the tiny geen-spaces that usually surround a conventional condominium or office building. Therefore, residents or staff are more likely to go up onto the roof-top garden than to convene on the tiny yard adjacent to the parking lot.

They can also reduce the amount of heat coming off urban areas. Just imagine the difference in temperature between the grass in a park and the cement on the sidewalk. A living roof also helps regulate internal building temperature, keeping it cooler in the summer and warmer in the winter..

As green building in general gains popularity, more and more developers are looking at the benefits of green roofs. Green roofs can be heavy, and some existing buildings cannot support the load. That is why it is best if the possibility of a green roof is considered early on in the design process.