Glass Skylights

The skylight glass advantages

The skylight glass has better properties than the plastic skylights. Glass is more durable than plastics and does not discolor.
Positive is also, that glass doesn´t let the ultraviolet radiation through that much.
The natural glass, even being transparent to UVA light (380-315 nm), the safe UV spectrum, is opaque to UVB light (315-280 nm), the most dangerous UV spectrum causing the skin cancer.

The skylight glass disadvantages

Glass usually is a fragile material therefor the skylight glass is always either tempered and laminated (or both) to achieve better features.

Laminated skylights vs. tempered skylights

Both laminating or tempering treatments try to achieve a glass that doesn´t break in thousands of sharp small pieces (the same approach as the automotive glass producers follow to achieve as safe glass as possible) when broken.
The laminated (or plasticated or tempered) glass breaks (of course), but it doesn´t break in dangerous shark teeth pieces but large, edgeless and obtuse pieces that do not hurt anyone.
Glass is preferred by many people because it doesn't scratch. It can be single, double or triple glazed with energy-saving low-emission (low-E) material. The low-E coating is a thin layer of metal oxide sprayed onto the glass forming a very efficient energy-saving film. It is practically invisible for the people (glass is still transparent), the sun has no barriers to pass through the glass in, but then the glass acts as a mirror and reflects the light and heat back to the room if it wants to leave again. Herewith the low-E glasses reduce substantially the heat loss.