Glass vs Polycarbonate Greenhouses: Which is Better?
Written by Matt W, Co-Founder of Greenhouse Stores | Fact-Checked by Matt
After 16 years selling greenhouses and processing over 150,000 customer orders, the single most common question we get is: "Should I buy glass or polycarbonate?" The short answer? For most UK gardeners, Toughened Glass is the better choice because it withstands our windy weather far better than lightweight plastic — we've seen polycarbonate panels lift in gusts as low as 45mph on exposed sites, while toughened glass holds firm. However, Polycarbonate is the safest choice if you have young children, pets, or are buying for a school or public allotment.
While glass is the heavy-duty standard for British gardens, polycarbonate offers specific safety benefits. This guide compares the technical specifications, thermal performance, and wind resistance of both glazing types — plus a hybrid option — to help you decide. You can also 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, rain, and storms far better than polycarbonate.
- Polycarbonate is 200 times stronger than glass and won't shatter, making it 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's 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.
Polycarbonate Greenhouses: The Safety Choice
Polycarbonate is a thermoplastic polymer that is virtually unbreakable — 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, dogs running around, or if you are buying for a nursery, school, or allotment where safety regulations are strict, polycarbonate is the answer.
The Advantages
- Safety First: Polycarbonate is approximately 200 times stronger than glass. It does not shatter, making it the only responsible choice for family gardens where the risk of breakage is high.
- Superior Insulation: Twin-wall polycarbonate acts like double glazing. The honeycomb structure traps air, providing a thermal barrier that keeps the greenhouse 5–8°C warmer than a glass equivalent during winter. According to the Royal Horticultural Society, maintaining even a small temperature advantage over winter can extend 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, removing 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 while allowing beneficial light through for photosynthesis.
- Lightweight: Twin-wall polycarbonate panels weigh roughly 1.2kg per square metre, compared to 7.5kg per square metre for 3mm toughened glass — making DIY assembly 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 calls us 6 months later after a storm has popped panels out or buckled the frame. Polycarbonate is light — that's great for assembly, but terrible for wind resistance.
If you're in a coastal, highland, moorland, or elevated position where the greenhouse will be exposed to regular high winds, polycarbonate is not suitable. I'd recommend a Toughened Glass Greenhouse with Glazing Bar Capping or a Wooden Greenhouse — both are 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 & 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 (40% more aluminium than standard greenhouses) and cantilever bracing. It is wind tested to 90mph.
Wind Rating: 90mph+ |
View Full Range: Polycarbonate Greenhouses
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 isn't looks — it's structural performance. Standard horticultural glass (which breaks into dangerous shards) is outdated. At Greenhouse Stores, we focus on 3mm Toughened Safety Glass, which 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 where wind is a constant issue, this weight helps keep the structure grounded. We've 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, traditional look that polycarbonate cannot replicate.
- Safety (Toughened): Unlike standard 3mm horticultural glass, toughened glass granulates into small, relatively harmless pebbles if broken, rather than jagged shards. It meets BS 6206 Class A safety standards.
- Longevity: Glass doesn't yellow, cloud, or degrade over time. A toughened glass greenhouse will look the same after 15 years as it did on day one, while 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 & family safety. Why I Recommend It: The Venus 5000 is the UK's favourite size (8x6) and this model comes with full-length Toughened Safety Glass. It gives you the traditional look and clarity of glass without the danger of dangerous shards if broken.
Safety: Granulates if broken (Child Safe) |
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 (costs around £15–£30 depending on size) and add a small greenhouse heater (a 2kW electric heater costs roughly £40–£80 to buy and around £0.50–£1.00 per night to run).
That gives you a permanent, solid structure year-round that can be adapted for winter at minimal cost. A polycarbonate greenhouse destroyed by one bad storm is a far more expensive problem to solve.
For a full breakdown of winter heating options, read our Greenhouse Heating Guide.
View Full Range: Toughened Glass Greenhouses
The Best of Both Worlds: Hybrid Greenhouses
A hybrid greenhouse uses polycarbonate roofing for insulation and clear sides for visibility — combining the strengths of both materials.
If you can't decide between the safety and insulation of twin-wall polycarbonate and the clarity of glass, 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, allowing you to see your plants while sitting in the garden.
This configuration gives you the thermal efficiency of a twin-wall roof (retaining up to 40% more heat than a single-glazed glass roof) without sacrificing 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 don't 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) and crystal-clear polycarbonate on the sides (so you can see your plants).
Glazing: Twin-Wall Roof / Clear Sides |
View Model: Palram Canopia Hybrid Greenhouses
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, won't 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 |
Verdict
The "better" greenhouse depends entirely on your specific location and needs:
- Choose Polycarbonate if: Safety is top of your list. If you have small children running around nearby or your allotment association requires you only have a polycarbonate greenhouse.
- Choose Toughened Glass if: You want the best choice for the UK gardener. Our weather isn't exactly beautiful year-round — we get gales, storms, high winds, rain and snow. Toughened Glass is rigid, strong and tough, meaning it handles bad weather with ease. It's also very safe: if it does break, it shatters into small harmless pebbles rather than dangerous shards.
- Choose Palram Hybrid if: You want the insulation of a polycarbonate roof 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 step by step.
Frequently Asked Questions
Is polycarbonate or glass better for a greenhouse in the UK?
Toughened glass is the better choice for most UK gardens because of its superior wind resistance. Glass weighs around 7.5kg per square metre compared to 1.2kg for polycarbonate, which gives the frame far more rigidity in storms. The one exception is if safety is your top priority — polycarbonate is 200 times stronger than glass and won't shatter, making it the right option for homes with young children, schools, or allotments with safety regulations.
How much warmer is a polycarbonate greenhouse than glass?
A twin-wall polycarbonate greenhouse typically stays 5–8°C warmer than a single-glazed glass equivalent in winter. The honeycomb structure of twin-wall panels traps air between two layers, acting like double glazing. That said, you can close this gap on a glass greenhouse for around £50–£100 by adding 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 or exposed sites. The lightweight panels (around 1.2kg per m²) can lift, flex, or pop out of the frame in sustained winds above 40–45mph. If you're in a coastal, hilltop, or open position, choose a toughened glass greenhouse with glazing bar capping instead. For the most extreme sites, the Elite Titan 800 is wind-tested to 90mph+.
Does polycarbonate greenhouse glazing go yellow over time?
Yes, polycarbonate panels typically start to yellow and cloud after 8–10 years. UV-stabilised panels (like those from Palram Canopia) slow the process, but degradation is unavoidable over time. 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 Palram Canopia Hybrid series is the most popular example. The twin-wall roof diffuses harsh overhead sunlight and retains up to 40% more heat than a glass roof, while the clear sides give you visibility of your plants. It's a good compromise if you want some insulation benefits without fully committing to an opaque polycarbonate design.
