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Natural Light Materials

The most common form of natural roof lighting used in commercial and industrial buildings comprises single skin, glass-reinforced plastic (GRP) sheets matching the profile of the metal roofing, running from ridge to eaves in continuous lengths of up to 12 m, sometimes longer. For other applications such as housing, polycarbonate sheeting is more commonly used. Polycarbonate is available in stock sheet lengths of up to 7.2 metres.

Profiled PVC roof lights are now rare as they suffer from embrittlement when exposed to UV.

GRP combines polyester resin and chopped glass fibre. AS/NZS 4256.3 requires sheets to contain a minimum of 22% glass fibre by mass and to be marked with their classification and weight.

Comparison of GRP and Polycarbonate.

GRPPolycarbonate
Available in all profilesAvailable in limited profiles
Available in long runAvailable in standard lengths
Available in different thicknessesAvailable in one thickness
Durability >25 yearsDurability >25 years
Will lose transparency with ageWill maintain initial transparency
Gives diffuse lightGives direct light
Thermal expansion 2 x that of steelThermal expansion 5x that of steel
Available in tinted or opaqueAvailable tinted
Reasonable light transparencyExcellent light transparency
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Polycarbonate is more popular for shorter runs and continuous widths, where clarity and stable appearance are considered an aesthetic attribute.

Stand-alone and flat-sheet roof lights may be manufactured from translucent or transparent polycarbonate, acrylic, or glass sheeting.

/cop/natural-light/natural-light-materials
Revision Category: 
3 - Substantial change to recommendation
Revision Detail: 

COP clause 11. Natural Light has been revised, which includes the clause previously titled "Materials".

Draft Clause: 
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