shingles which generate electricity as well as cover the roof. There are also solar systems available that generate hot water or hot air and which can also act as a roof covering. More complex systems may carry out all of these functions: generate electricity, recover thermal energy, and also act as a roof covering. Solar systems can be integrated with roofs by: integration in the covering of pitched roofs, e.g. solar shingles, mounting on an existing roof, e.g. solar panel on a tile roof, integration in a flat roof membrane using heat welding (e.g. PVC) or mounting on a flat roof with a construction and additional weight to prevent uplift from wind. Gallery of roof shapes Gallery of significant roofs See also List of roof shapes Domestic roof construction Roof cleaning Tensile architecture Thin-shell structure List of Greco-Roman roofs References Structural engineering Structural system