Polycarbonate has become the preferred glazing material for greenhouses across Australia — replacing glass in both new builds and retrofits. Lighter, stronger, better insulating, and far more UV-resistant, it creates a better growing environment while reducing energy costs and maintenance. Here’s everything you need to know.
Why Polycarbonate Is Better Than Glass for Greenhouses
- Better thermal insulation — multiwall polycarbonate traps air between layers, reducing heat loss and cutting heating costs by up to 30% compared to glass
- Light diffusion — polycarbonate diffuses sunlight evenly, eliminating hot spots that can scorch plants; glass transmits harsh direct light
- UV protection — built-in UV coating blocks harmful UV rays while maintaining high light transmission, protecting plants and extending growing seasons
- Impact resistance — up to 80 times more impact-resistant than glass; won’t shatter in hail or storms
- Lightweight — roughly half the weight of glass, reducing structural load and making installation easier
- Longer growing season — superior insulation keeps temperatures stable, allowing year-round growing in most Australian climates
Which Polycarbonate Sheet Is Best for a Greenhouse?
Twin-Wall Polycarbonate (Most Popular)
Twin-wall polycarbonate is the most widely used greenhouse glazing material. Its internal air chamber delivers excellent thermal insulation (R-value significantly higher than single-layer glass), while still transmitting up to 82% of light. Available in 6mm and 10mm thickness — 10mm is recommended for year-round Australian greenhouses.
- Best for: Walls and roof panels on permanent greenhouses
- Key benefit: Best balance of insulation, light transmission, and cost
Multiwall Polycarbonate (Maximum Insulation)
For growers in cooler climates or those running heated greenhouses, multiwall panels with 3+ layers deliver superior thermal performance. The additional air chambers significantly reduce heat loss, lowering ongoing heating costs.
- Best for: Heated greenhouses in Victoria, Tasmania, or high-altitude locations
- Key benefit: Lowest heat loss; best energy efficiency
Corrugated Polycarbonate (Budget Option)
Corrugated polycarbonate sheets are a cost-effective option for simple greenhouse structures, cold frames, and garden shelters. They offer good light transmission and impact resistance, but less thermal insulation than multiwall panels.
- Best for: Budget builds, cold frames, and unheated seasonal shelters
- Key benefit: Lowest cost; easy to install
Bendable Corrugated Panels (Curved Structures)
For curved or tunnel-style greenhouse frames, 1.2mm bendable corrugated polycarbonate panels are specifically designed to flex around curved profiles without cracking.
- Best for: Tunnel greenhouses and curved hoop structures
- Key benefit: Flexible; conforms to curved frames
Key Specifications for Greenhouse Polycarbonate
| Property | Twin-Wall 6mm | Twin-Wall 10mm |
|---|---|---|
| Light transmission | Up to 82% | Up to 80% |
| Weight | 1.15 kg/m² | 1.7 kg/m² |
| Service temperature | -40°C to +120°C | -40°C to +120°C |
| UV protection | 50μm coating | 50μm coating |
| Warranty | 10 years | 10 years |
Greenhouse Installation Tips
- UV side faces out — always install with the UV-protected side facing the sun (marked on the sheet)
- Seal open ends — use end caps and aluminium tape to seal the internal channels of multiwall sheets; open ends allow moisture and insects to enter
- Allow for expansion — polycarbonate expands in heat; leave 3–5mm clearance in all fixings
- Overlap correctly — for corrugated sheets, overlap by at least one corrugation at side joints
- Clean gently — use mild soap and water only; avoid abrasive cleaners or solvents that can damage the UV coating
Clear vs Opal for Greenhouses
- Clear — maximum light transmission; best for most plants and cooler climates where solar gain is welcome
- Opal/diffused — softens and diffuses light evenly; reduces hot spots; better for sensitive plants or north-facing greenhouses in warmer climates
Shop Greenhouse Polycarbonate at ExcelitePlas
ExcelitePlas stocks a full range of polycarbonate sheets for greenhouse applications — from twin-wall panels to bendable corrugated sheets for curved structures. Available cut to size with fast delivery across Australia from our Dandenong South Warehouse.
Contact our team for expert advice on the right sheet for your greenhouse project.
