Glass vs Polycarbonate Greenhouses: Which?
After 16 years and over 150,000 customer orders, one question comes up more than any other. "Should I buy glass or polycarbonate?" For most UK gardeners, toughened glass is the better choice. It withstands our windy weather far better than lightweight plastic. We have seen polycarbonate panels lift in gusts as low as 45mph on exposed sites. Toughened glass holds firm. Polycarbonate is the safest choice if you have young children, pets, or need it for a school or allotment.
While glass is the heavy-duty standard for British gardens, polycarbonate offers specific safety benefits. This guide compares the thermal performance and wind resistance of both glazing types. We also cover a hybrid option to help you decide. Browse our full range of greenhouses to compare models side by side.
Key Takeaways
- Toughened glass is the better all-round choice for UK gardens. Its weight adds rigidity, and it handles wind and storms far better than polycarbonate.
- Polycarbonate is 200 times stronger than glass and will not shatter. It is the only responsible option where child safety or allotment regulations apply.
- Twin-wall polycarbonate keeps your greenhouse 5–8°C warmer than a single-glazed glass equivalent in winter. But it is vulnerable to lifting in high winds.
- Hybrid greenhouses (like the Palram Canopia Hybrid) use twin-wall roofing for insulation and clear sides for visibility. A practical middle ground.
- Glass insulation is cheap to fix. Bubble wrap and a small heater in winter costs far less than replacing a wind-damaged polycarbonate structure.
Installer's Note
We have fitted both glass and polycarbonate greenhouses for over a decade. In our experience, toughened glass wins for most UK gardens. The extra weight makes a real difference when the wind picks up. Polycarbonate is lighter to handle on install day. But we have been called back too many times to refit panels after storms. If safety around children is your main concern, polycarbonate is the right call. For everything else, we recommend toughened glass.
Polycarbonate greenhouses: the safety choice
Polycarbonate is a thermoplastic polymer that is virtually unbreakable. It is roughly 200 times stronger than standard glass.
At Greenhouse Stores, we class this as the definitive Safety Choice. It is the primary option when safety is your absolute top priority. If you have small children playing football in the garden or dogs running around, polycarbonate is the answer. Schools, nurseries, and allotments with strict safety regulations also require it.
The advantages
- Safety first: Polycarbonate is roughly 200 times stronger than glass. It does not shatter. This makes it the only responsible choice for family gardens where breakage risk is high.
- Superior insulation: Twin-wall polycarbonate acts like double glazing. The honeycomb structure traps air, providing a thermal barrier. It keeps the greenhouse 5–8°C warmer than a glass equivalent during winter. The Royal Horticultural Society notes this extends your growing season by 4–6 weeks.
- Light diffusion: Unlike clear glass, twin-wall polycarbonate diffuses sunlight. This scattering effect prevents hot spots and leaf scorch. It removes the need for whitewashing or shading blinds during high summer.
- UV protection: High-quality panels, such as those used by Palram Canopia, block 99.9% of harmful UV radiation. They still allow beneficial light through for photosynthesis.
- Lightweight: Twin-wall panels weigh roughly 1.2kg per square metre. Compare that to 7.5kg per square metre for 3mm toughened glass. DIY assembly is significantly easier.
Matt's Tip: Don't Buy Polycarbonate for Windy Sites
This is one of the most common mistakes I see. A customer buys a polycarbonate greenhouse because they like the insulation. Then they call us six months later after a storm has popped panels out or buckled the frame. Polycarbonate is light. That is great for assembly, but terrible for wind resistance.
If you are in a coastal, highland, moorland, or exposed position, polycarbonate is not suitable. I would recommend a toughened glass greenhouse with glazing bar capping. A wooden greenhouse is also far more durable in exposed conditions.
For more detailed advice on location and protection, read our Greenhouse Wind Damage Guide.
| Elite Titan 800 Greenhouse | Matt's Pick for Windy Gardens |
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Best For: Coastal, hilltop and exposed locations. Why I Recommend It: If wind is your worry, this is the solution. It uses a Core-Vect frame with 56mm thick bars. That is 40% more aluminium than standard greenhouses. It includes cantilever bracing and is wind tested to 90mph. Wind Rating: 90mph+ Price: From £1,759 |
Toughened glass greenhouses: the traditional choice
For most UK gardeners, toughened glass is the strongest and most weather-resistant greenhouse glazing available.
The aesthetic of sparkling clear glass is a big draw for many buyers. But the real advantage is not looks. It is structural performance. Standard horticultural glass breaks into dangerous shards and is outdated. At Greenhouse Stores, we focus on 3mm toughened safety glass. This is 4–5 times stronger than standard horticultural glass of the same thickness.
The advantages
- Wind stability: 3mm toughened glass weighs approximately 7.5kg per square metre. That extra mass adds significant rigidity to the aluminium frame. In coastal or hilltop locations, this weight helps keep the structure grounded. We have had customers in Cornwall and the Scottish Highlands report their glass greenhouses standing firm through 70mph+ gusts.
- Clarity and aesthetics: Glass offers up to 90% direct light transmission with near-100% optical clarity. If your greenhouse is a feature in a manicured garden, glass provides that classic look. Polycarbonate cannot replicate it.
- Safety (toughened): Unlike standard 3mm horticultural glass, toughened glass granulates into small, relatively harmless pebbles if broken. It meets BS 6206 Class A safety standards.
- Longevity: Glass does not yellow, cloud, or degrade over time. A toughened glass greenhouse will look the same after 15 years as it did on day one. Polycarbonate panels typically start to cloud after 8–10 years.
| Vitavia Venus 8x6 Toughened | Best Selling Glass Greenhouse |
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Best For: Classic British gardens and family safety. Why I Recommend It: The Venus 5000 is the UK's favourite size (8x6). This model comes with full-length toughened safety glass. It gives you the traditional look and clarity of glass without the danger of shards if broken. Safety: Granulates if broken (child safe) Price: From £649 |
The insulation vs toughness reality
Critics often point out that glass has lower thermal retention than twin-wall polycarbonate. The insulation argument is valid. But in the UK, toughness is more important.
A glass greenhouse with poorer insulation can be fixed cheaply. Put up bubble wrap insulation in the frosty winter months. It costs around £15–£30 depending on size. Add a small greenhouse heater. A 2kW electric heater costs roughly £40–£80 to buy. It costs around £0.50–£1.00 per night to run.
That gives you a permanent, solid structure year-round. You can adapt it for winter at minimal cost. A polycarbonate greenhouse destroyed by one bad storm is a far more expensive problem.
For a full breakdown of winter heating options, read our Greenhouse Heating Guide.
The best of both worlds: hybrid greenhouses
A hybrid greenhouse uses polycarbonate roofing for insulation and clear sides for visibility. It combines the strengths of both materials.
Cannot decide between polycarbonate safety and glass clarity? A hybrid design is a practical middle ground.
The Palram Canopia Hybrid series uses a split glazing system:
- Roof: 4mm twin-wall polycarbonate to diffuse intense overhead sun and retain rising heat.
- Sides: Crystal-clear polycarbonate panels that look like glass. You can see your plants while sitting in the garden.
This configuration gives you the thermal efficiency of a twin-wall roof. It retains up to 40% more heat than a single-glazed glass roof. You do not sacrifice the visual appeal of clear sides.
| Palram Canopia Hybrid 6x8 | The Best of Both Worlds |
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Best For: Growers who want insulation and a view. Why I Recommend It: You do not have to choose between a warm roof and clear walls. The Hybrid uses twin-wall polycarbonate on the roof to prevent scorch and retain heat. The sides are crystal-clear polycarbonate so you can see your plants. Glazing: Twin-Wall Roof / Clear Sides Price: From £519 |
Comparison at a glance
| Feature | Toughened Glass | Twin-Wall Polycarbonate |
|---|---|---|
| Wind Resistance | Excellent (heavy, rigid) | Moderate (lightweight, can lift) |
| Thermal Insulation | Low (fixable with heaters/wrap for £50–£100) | High (5–8°C warmer, extends season 4–6 weeks) |
| Light Transmission | ~90% direct, near-100% optical clarity | ~82–90% diffused (prevents hot spots) |
| Impact Strength | High (4–5x stronger than horticultural glass) | Extreme (200x stronger than standard glass) |
| Safety | Good (granulates into pebbles, BS 6206) | Excellent (the safety choice, will not shatter) |
| Risk of Scorch | High (may need shading in summer) | Low (natural light diffusion) |
| Weight per m² | ~7.5kg (adds structural rigidity) | ~1.2kg (easy DIY assembly) |
| Longevity | 25+ years (no yellowing or clouding) | 10–15 years (panels cloud after 8–10 years) |
| Best For | Most UK gardens, windy/exposed sites | Families with children, schools, allotments |
Which glazing should you choose?
The better greenhouse depends entirely on your location and needs:
- Choose polycarbonate if: Safety is top of your list. You have small children running around or your allotment association requires polycarbonate glazing.
- Choose toughened glass if: You want the best choice for UK weather. We get gales, storms, high winds, rain and snow. Toughened glass is rigid and strong. It handles bad weather with ease. If it does break, it shatters into small harmless pebbles.
- Choose a hybrid if: You want polycarbonate roof insulation but still want the visual clarity of glass-like side panels.
Not sure which size you need? Our Greenhouse Buying Guide walks you through sizing, positioning, and budgeting.
Frequently asked questions
Is polycarbonate or glass better for a greenhouse in the UK?
Toughened glass is the better choice for most UK gardens. It offers superior wind resistance. Glass weighs around 7.5kg per square metre. Polycarbonate weighs just 1.2kg, giving the frame far less rigidity in storms. The one exception is where safety is your top priority. Polycarbonate is 200 times stronger than glass and will not shatter. It is the right option for homes with young children, schools, or allotments.
How much warmer is a polycarbonate greenhouse than glass?
A twin-wall polycarbonate greenhouse stays 5–8°C warmer in winter. The honeycomb structure of twin-wall panels traps air between two layers. It acts like double glazing. You can close this gap on a glass greenhouse for around £50–£100. Add bubble wrap insulation and a small electric heater during the coldest months.
Can polycarbonate greenhouses withstand strong winds?
No. Polycarbonate greenhouses are not suitable for windy sites. The lightweight panels (around 1.2kg per m²) can lift, flex, or pop out of the frame. This happens in sustained winds above 40–45mph. If you are in a coastal, hilltop, or open position, choose toughened glass with glazing bar capping. For extreme sites, the Elite Titan 800 is wind-tested to 90mph+.
Does polycarbonate greenhouse glazing go yellow over time?
Yes. Polycarbonate panels start to yellow after 8–10 years. UV-stabilised panels slow the process, but degradation is unavoidable. Toughened glass does not yellow, cloud, or degrade. A glass greenhouse will look the same after 15–20 years as it did on day one.
What is a hybrid greenhouse?
A hybrid greenhouse uses twin-wall polycarbonate on the roof and clear polycarbonate on the sides. The twin-wall roof diffuses harsh overhead sunlight. It retains up to 40% more heat than a glass roof. The clear sides give you visibility of your plants. It is a good compromise if you want insulation benefits without a fully opaque design.
