It may seem strange to count sod among current trends, since sod roofs have been around for hundreds of years. In Scandinavia, sod roofs were ubiquitous through the 17th century and only buildings with roofs too steeply pitched for sod used wooden planks or shingles. The Scandinavian sod roof consisted of a substrate of wooden boards covered with several layers of birch bark to make the roof watertight, with sod used as the top layer to keep the bark in place.
Modern green roofs may use different materials, but the theory behind them is much the same. They use multiple layers of specially designed components to protect the underlying structure and to keep vegetation in place. While components vary from site to site, green roofs typically include a root barrier membrane, special fabric layers for water distribution and drainage, a stabilization system to protect the installation from the wind, and a special lightweight growth medium.
Green roofing is a growing part of the industry, at least partly because it has tapped into increased ecological awareness. In addition to its aesthetic appeal, a green roof can provide significant insulation value, help to control water runoff and, by shielding underlying roof components, materially extend the useful life of the roof.
Plastics are not generally thought of as ecologically friendly materials, but recycling plastics into roofing materials is an excellent way to reuse a substance that would otherwise enter the environment and stay there for a very long time. In the past, however, plastic shingles made few inroads into the roofing market. The plastic simply looked too much like plastic, an artificial material with no aesthetic appeal. To achieve even a marginally natural look, roofers had to artfully mix shingles from different pallets. Without careful installation, the finished product was a patchy roof that looked fake and that detracted from a property’s curb appeal and resale potential.
Manufacturers have come a long way in an effort to produce a more natural-looking product, both by improving the look of individual shingles and by supplying pallets that are mixed at the factory. Despite greatly improved appearance, plastic’s high initial cost of materials remains an obstacle. Installation, however, is no more difficult or expensive than installing composite shingles. Once installed, plastic shingles have many virtues, including excellent impact and fire ratings and a useful life of several decades. That longevity ultimately makes a plastic roof a cost-effective option over the long term, especially when compared to the 15-year life expectancy of a roof sheathed in asphalt shingles.
Metal is yet another material that has been used in roofing in the past with mixed results. Previous generations of metal roofs involved panels that were caulked and screwed directly into the roof’s structural components, a recipe for disaster. Problems developed when the metal panels expanded and contracted in response to temperature changes, leading to leaks and splitting, especially in thin, light panels.
Manufacturers have addressed this problem with sophisticated systems for attaching panels, generally with concealed clips that allow panel movement without sacrificing tightness to the weather. With proper installation, metal roofing is more durable than asphalt shingles and should require little or no maintenance. Traditional materials like galvanized steel and copper are still very much in use, but they have been joined by stainless steel, aluminum and blends of zinc, aluminum and steel. At the same time, the development of durable ceramic coatings and long-lasting paints has helped to eliminate problems with rust and corrosion, while enhancing the energy efficiency of the roof and providing a wealth of options for the roof’s texture and color.