Greenhouse growers often believe that it is easier to grow moss on top of a fibreglass greenhouse than plants inside it! “Fibre-show” has plagued the perceptions of fibreglass for years. Zammit Roofing’s revolutionary Wonderglas GC however, is set to change how the world sees fibreglass.

Wonderglas GC features a unique gel coating which prevents fibre-show and maintains high levels of light transmission for many years.


  • Spans up to 2m.
  • Unique greenhouse profile available.
  • Customised light transmission figures available.
  • Maximum durability.
  • Easily curved for superior greenhouse design.
  • Maintains light transmission.
  • Can be incorporated into Dual Roof system for ultimate thermal insulation.
  • 25 year warranty against “fibre-show”.

Available Profiles

All current profiles such as Corrugated, Trimdek, and most superseded profiles are available. Zammit Roofing can also supply the unique “greenhouse profile”. This profile features shallow, steep ribs to maximise spanning capacity, whilst minimising light transmission loss through shade. The unique connection between sheets is also designed to maximise light transmission through minimal overlap on side ribs.

Custom profiles are often produced for applications such as growing trays.


Wonderglas GC features excellent spanning capabilities, unmatched by other translucent materials such as glass, polythene film and profiled polycarbonate.

1200 1.2 0.9M
1500 1.5 1.2M
1800 1.8 1.5M
2400 2.4 2.0M
Dual Roof 3.2 2.0M
Grow Tray 2.4 2.0M

The above spans are recommended for wind loads up to 1 kPa. For high wind or cyclonic areas, please contact Zammit Roofing.

Thermal Insulation

Wonderglas GC has a K-Value of 5.8 W/m2.K. When incorporated into the Dual Roof system, this reduces to 2.0 W/m2.K – the lowest of any greenhouse cladding material!

Wonderglas GC is compatible with anti-condensation coatings and white wash.

Light Transmission

Zammit Roofing’s range of Wonderglas GC sheeting for greenhouses includes special additives to aid light diffusion. This reduces shaded areas within the greenhouse and minimises plant damage associated with sun burn.

For applications where maximum light transmission is not favourable, Zammit Roofing can manufacture Wonderglas GC sheeting with customised light transmission figures.

1200 88% 86%
1500 86% 85%
1800 85% 82%
2400 84% 81%
Dual Roof 82% N/A
Grow Tray 0% 0%


Wonderglas GC sheeting can be safely curved to a radius of 4m. For greenhouses with higher curving radii, please contact Zammit Roofing.

Expansion Data

Materials Expansion Comparison.  0° to 40° Temperature Variation.  Sheet Length 12 metres
Fibreglass Polycarbonate Steel Aluminium
Thermal Expansion 14.4mm 32.4mm 5.8mm 11.5mm
Thermal Co-efficient 3.0 x 10-5 cm/cm°C 6.75 x 10-5 cm/cm°C 1.2 x 10-5 cm/cm°C 2.4 x 10-5 cm/cm°C

Physical Properties

Tensile Strength 80 Mpa
Impact Strength 8 Joules
Shear Strength 90 Mpa
Modulus of Elasticity 5000 Mpa
Compressive Strength 135 Mpa
Flexural Strength 150 Mpa
Specific Gravity 1.45
Thermal Expansion 3.0 x 10-5 cm/°C
Water Absorption .2% in 24hrs./26°C
Thermal Conductivity 0.158 watt/m°C
Curved Roof Radius 2400g/m2 “Custom Orb” and “Trimdek”
Minimum Radius 4.0 Metres
Recommended Service Temperature Range -20° to +95°C


Dual Roof System

  • Excellent energy savings
  • Significantly reduced condensation
  • Ideal for heated greenhouses

Zammit Roofing’s unique Dual Roof System combines the excellent spanning and solar optical properties of Wonderglas GC, with thermal insulation unmatched by other cladding materials.

  • Light transmission: 82%
  • K-Value: 2.0 W/m2.K

The Zammit Roofing Dual Roof System uses the fundamental principals of double-glazing to create a simple, yet functional skylight system. Dual Roof has specifically been designed for the Australian climate, with simplicity and ease of installation a high priority. Whilst the system is not unique in theory, in practice it provides a long-term cost saving and environmental benefit for years to come.