Global climate change is here. In my local newspaper here in western North Carolina I read today that 2004 was the fourth hottest on record. For the last decade, this has been the case with the ten warmest years since the 1990’s. This report was issued by the U.N. Weather Agency in December of 2004.

Here in North Carolina, the minimum temperatures have tended to increase during this period. This is especially true in urban and built-up areas. To keep buildings cooler and more comfortable during hot summers and warmer in the winter months, the solution is to build roof gardens using succulents.

Though I have written about roof garden earlier, this climate report should serve as a wake-up call to those building homes in urban areas. Anyone planning new construction could benefit from roof gardens.

Recently, a roof garden was installed at Harvard University for a building that serves as housing for students in graduate programs. This roof garden covers over ten thousand square feet, and has roughly one plant per square foot.

Nationwide, roof gardens are being installed in most areas of the U.S. Seattle has promoted their use in all new public buildings. Some municipalities are encouraging the construction of roof gardens by offering incentives. Among these are Chicago, New York City, Portland, Oregon, and Washington, DC. The state of Maryland is also doing the same.

These are also becoming more common in Canada, and are also catching on in other parts of the world, including the Orient. In Germany, these are used
extensively.

In terms of cost, a roof garden will cost considerably more than a conventional roof. However, they last much longer, which lowers the actual cost over time. In addition, if one factors in the savings on heating/cooling bills, the upfront price tag of the roof isn’t as high as it seems.

When planning a roof garden, an important factor is weight. You need to work closely with structural engineers to determine the maximum weight and how it should be distributed.

While one of the main reasons for planting roof gardens is to reduce cooling and heating cost, these also serve another valuable role that you can’t put a price tag on. They minimize the amount of storm run-off reaching paved areas, and in effect can reduce the risks of flooding during heavy rainstorms. Typically, these gardens are designed with special drainage systems to hold lots of excess water, which eventually drains through the planters to reach the plants. By doing that, it minimizes the environmental effect of excess run-off that can result in heavily built-up areas.

Let’s look at some of the succulents that are most commonly used for roof gardens. Among these are the Sempervivums, and many kinds of stoloniferous sedums and other kinds that form runners. The best choices would be low-growing sedums and other succulents. Of the sedums, the ones that are most commonly used are Sedum John Creech, Sedum pluricaule Rose Carpet, Sedum sexangulare, and Sedum spurium.