The first thing to note is that glass comes in flat panes or insulated units. Curved glass is highly specialised and very expensive to manufacture. It is not available in 3D shapes. Glass weighs heavy and this can be an issue when looking at larger areas, unless the structure has been specifically designed to take the weight.
Polycarbonate is everywhere! We can find it in eye glasses, medical devices, lighting fixtures, crash helmets and riot shields. Here’s the science - It is a naturally transparent amorphous thermoplastic, which means it is great at transmitting light and is almost as effective as glass. It’s strong, durable, weatherable and flexible enough to be formed into 3 dimensional domes.
Glass and polycarbonate are both naturally clear, providing great clarity and light transmission with direct light and no diffusion. However, glass can offer diffusion with reduced levels of light transmission if it is manufactured with a diffusing interlayer and Polycarbonate can be manufactured with a tint. This means it can provide privacy and diffusion, but this in turn will affect the light transmission.
Glass can be exposed to sunlight and the elements over many years with no deterioration in it’s aesthetic properties and has optimum resistance to UV degradation. Normal weathering has almost no effect.
Correctly sealed double-glazed glass units should be designed, manufactured and installed to minimise the risk of condensation. Units of glass can comprise of either double or triple layers and are available with coatings on one surface facing into each cavity or solar control coatings on the outer pane to improve thermal performance.
If noise control is important, then it would be worth noting that heavier materials provide better acoustic performance, meaning that glass would be a better option for sound reduction or a rooflight that combines both glass and polycarbonate such as Coxdome flat roof window with dome
Polycarbonate does need protection from the effects of UV to retain light transmission and resist discoloration. In good quality polycarbonate, there is an integrated UV-absorbing surface layer. This means it can retain light transmission and resist discoloration. Polycarbonate is a strong, high performance material with good long-term prospects in ideal conditions. Here’s some more science - Polycarbonate rooflights are made of a hygroscopic material, which naturally absorbs moisture and increases the internal humidity and risk of condensation. This means that ventilation in the rooflight is essential to avoid the build-up of moisture. The number of skins on a polycarbonate rooflight can be increased so that the thermal performance is similar to the glass rooflight.
Toughened and laminated glass can be durable and strong enough in certain grades to be use to walk on. Rooflights should always contain safety glass which means it must be wired, toughened, laminated or a combination of all. Toughened option better for resistance to damage and cracking, but if it breaks, it will form several small rounded pieces which can fall into a building.
Polycarbonate’s strength means it has good resistance to evenly-distributed loads.
So, even with the many differences of glass and polycarbonate, they both have their benefits and suitability.
If you need any further help in deciding if Polycarbonate or Glass would be better for you, then please do not hesitate to call our knowledgeable team who will be happy to help you.
**Please note our offices will close for Christmas on 20th December 2019 and will reopen on 2nd January 2020.
All orders placed within this time will be processed upon our return. Merry Christmas & Happy New year from everyone at Rooflights & Skylights**