I HAVE GREEN fringes sticking out around the edges of my roof at home but that's not the same as the sedum-covered roofs that many eco warriors have installed over their heads. A sedum-covered roof attracts insects to control pests in your garden and it helps birds in the winter. Do it right and a sedum roof improves thermal performance and reduces noise. Some British suppliers offer turf-style segments for DIY roofers. The turf segments comes ready-sown with a mix of sedum plants that only grow to a limited height. This thick sedum blanket is laid over a waterproof membrance that inbihits root growth. Smooth, river-washed stones are often used to prevent sedum growing near the roof junctions which may cause damp patches over time. Known for their low-maintenance costs, a sedum roof costs around 40% more than a traditional roof.