Is It Better to Have Glass or Polycarbonate in a Greenhouse?

Choosing the right material for your greenhouse is essential for long-term performance, especially in New Zealand’s ever-changing weather conditions. Two of the most common greenhouse materials are glass and polycarbonate, and each offers distinct advantages depending on your gardening needs.

Here’s a detailed comparison to help you decide which material is better for your greenhouse in Auckland or anywhere across New Zealand.

1. Insulation and Heat Retention

• ✅ Polycarbonate: Polycarbonate provides excellent thermal insulation, especially in twin-wall panels. The layered design traps air between sheets, reducing heat loss at night—a key advantage during New Zealand’s cooler seasons.

• ⚠️ Glass: While it looks elegant, glass loses heat more quickly, leading to faster temperature drops at night. Unless external heating is used, plants may be exposed to more stress.

2. Light Transmission and Diffusion

• ✅ Polycarbonate: Offers even light diffusion, spreading rays throughout the greenhouse. While it has slightly lower light transmission than glass, it reduces harsh shadows and prevents hot spots that can damage plants.

• ⚠️ Glass: Provides high light clarity and direct sunlight, which benefits light-loving plants. However, it may cause uneven lighting and localized overheating in summer.

3. Durability and Weather Resistance

• ✅ Polycarbonate: Highly impact-resistant and flexible, making it ideal for windy or hail-prone regions. It’s less likely to crack and can be installed tightly with minimal gaps — perfect for New Zealand’s coastal climates.

• ⚠️ Glass: Traditional glass is fragile and prone to cracking or shattering. Tempered glass is more durable but also heavier and more expensive to install.

4. Cost and Maintenance

• ✅ Polycarbonate: Generally more affordable and easier to transport. However, it may scratch or degrade over time, especially under prolonged UV exposure — though most panels have UV protection.

• ⚠️ Glass: Higher upfront cost, but it’s easier to clean and can last for decades without losing clarity, provided it’s not damage