They are both quality systems, your project may dictate which is the best solution.
Composite systems offer a rigid one sheet fixing, everything is built into the panel, keeping installation costs to a minimum. Whilst the Built up system which offers more flexibility, a higher level of workmanship is also required to obtain the required results.
Cost and lead time may also need to be considered. The Built up system is the lower cost option with a quicker lead time, whilst the Composite is more costly and requires a slightly longer lead time. So if your project requires flexibility, the built up system offers this. If you want the quality built into the rigid panel and are prepared to wait a little longer the Composite is the option.
GRP is sold by weight and not thickness the 1.83kg/m2 (6oz) sheet is not commonly used and only achieves non fragility, when used in a double skin roof light with 2.44kg/m2.
The 2.44kg/m2 (8oz) is the minimum requirement to achieve Class C liner non-fragility during construction for most profiles and assemblies.They are suitable for projects that will require minimal roof access.
3.05kg/m2 (10oz) are resistant to damage during construction.They are suitable on projects where there is limited or controlled access needed after construction.
Fire Ratings Class 1 and Class 3 – with Class 1 being the standard for lining panels.
F.A.I.R.s Factory assembled insulating roof lights are available in both Double Skin and Triple Skin. However to Comply with Building Regulations Part L2 2006 Rooflights must have a maximum U-value of 2.2W/m2k. Double skin roof lights do not comply.