above angle angles appearance building corrugated corrugations exhaust pipes grooved grooves height high metal perspectives protection roof roofing rooftop safety security shadows shapes shopping centre shops sunlight ventilation exhaust pipes ventilation system capping cover covered covering edge exhaust-pipes exterior external roof-area roof-capping roof-whirlybird sky sunshine textures tiles tiling turbine-ventilator vent ventilation ventilation-exhaust-pipes ventilation-system ventilator vents whirlybird whirlybirds wind-turbine