Properties Double Glazed: Light transmission - 77%. Solar heat gain factor - 69%. Sound reduction (db) - 20. Thermal transmission (w/m2k) - 2.68. Triple Glazed: Light transmission - 70%. Solar heat gain factor - 60%. Sound reduction (db) - 22. Thermal transmission (w/m2k) - 1.78. Features • Polycarbonate rooflights comply with HSG 33 (Health and Safety in Roofwork) recommendations. • Patented high security screwbolt fixings. • Perimeter seal and screw fixing ensure Em-Dome™ rooflight is fully waterproof. • All polycarbonate Em-Domes™ use a minimum 3 mm thick glazing. • Acrylic Em-Domes™ have a minimum 3mm outer skin. • Inner skin thickness varies according to the dome size. • When installed in accordance with the manufacturers' recommendations, Em-Domes™ are expected to exceed the life of the roof covering. • Em-Domes™ are guaranteed against the effects of defective design, materials or construction for ten years, subject to certain conditions. To Fit Existing or Site Formed Circular Curb of 500mm (External Dimensions)