Introduction
When planning a glazing project—whether it is a skylight, greenhouse, canopy, partition wall, or safety barrier—the choice of material makes or breaks the outcome. Two of the most common options are polycarbonate (PC) sheets and tempered glass. Both offer transparency and durability, but they differ dramatically in weight, impact resistance, cost, and workability.
This article compares polycarbonate sheets and tempered glass across the dimensions that matter most to architects, contractors, and building owners. By the end, you will know exactly which material suits your specific application.
1. Weight: Polycarbonate Is Significantly Lighter
Polycarbonate sheets weigh roughly 1/12 to 1/15 as much as glass of the same thickness. A 6mm solid polycarbonate panel weighs about 7.2 kg/m², while 6mm tempered glass weighs approximately 15 kg/m². For overhead glazing in particular, lighter weight means:
- Smaller, less expensive support structures
- Easier handling and faster installation
- Reduced dead load on existing buildings during retrofits
- Lower shipping and logistics costs, especially for export projects
If you are working on a large-span roof, a second-story canopy, or a structure with limited load-bearing capacity, polycarbonate’s weight advantage alone can swing the decision.
2. Impact Resistance: Polycarbonate Wins by a Wide Margin
This is where the gap is largest. Solid polycarbonate sheets offer 200 to 250 times the impact resistance of glass. Even multiwall (hollow) polycarbonate panels withstand hail, wind-borne debris, and accidental collisions that would shatter tempered glass immediately.
Tempered glass is roughly 4 to 5 times stronger than annealed glass and breaks into small, relatively safe granules—but it still breaks. Polycarbonate, by contrast, is virtually unbreakable under normal service conditions. It is the material of choice for:
- Sports facilities and gymnasiums (ball impact)
- Hurricane-prone regions (flying debris)
- Machine guards and industrial safety shields
- Bus stops, train stations, and other public infrastructure
For safety-critical applications, polycarbonate is the clear winner.
3. Light Transmission: Comparable, with a Trade-off
Clear tempered glass transmits about 88 to 91% of visible light. Solid polycarbonate is close behind at 88 to 89% for transparent grades. Multiwall polycarbonate panels range from 25% to 82% depending on color, thickness, and structure—giving you design options that glass simply does not offer without expensive coatings or films.
The trade-off: polycarbonate diffuses light more than glass. For applications where you want crisp, undistorted views (storefronts, display cases), glass still holds an edge. But for daylighting—greenhouses, atriums, skylights—the slight diffusion of polycarbonate actually reduces harsh glare and distributes light more evenly across interior spaces.
4. Thermal Insulation: Polycarbonate’s Hidden Strength
Tempered glass (single pane) has a U-value of approximately 5.7 W/m²·K—poor insulation by modern standards. To match building codes, glass typically requires double or triple glazing with Low-E coatings and argon fills, which drives up cost and weight dramatically.
Multiwall polycarbonate panels, by contrast, achieve U-values as low as 1.5 to 3.9 W/m²·K in a single panel thanks to their built-in air cavities. A 16mm five-wall polycarbonate panel can outperform a double-glazed glass unit in thermal performance while weighing a fraction as much. For climate-controlled environments—greenhouses, swimming pools, sunrooms—polycarbonate delivers better insulation at lower cost.
5. Cost: Upfront and Lifetime
Polycarbonate sheets typically cost 20 to 50% less per square meter than tempered glass of comparable thickness. But the real savings go deeper:
- Lighter framing and substructure (less steel, less labor)
- Lower shipping costs (more panels per container)
- Fewer breakage losses during transport and installation
- Reduced long-term replacement costs (no spontaneous breakage from nickel sulfide inclusions, a known issue with tempered glass)
That said, glass has a longer track record of maintaining optical clarity over decades. Polycarbonate with proper UV protection carries a 10 to 15 year warranty, and modern co-extruded UV layers have largely solved the yellowing problem of older-generation panels.
6. Workability and Installation
Polycarbonate can be cut, drilled, cold-bent, and fabricated on site with standard woodworking tools. Tempered glass cannot be cut or drilled after tempering—every panel must be ordered to exact dimensions from the factory. If a measurement is off, you wait for a replacement.
For projects with curved designs (arched canopies, barrel vaults), polycarbonate can be cold-formed to a radius without heating. Tempered glass requires expensive hot-bending or lamination, adding weeks to lead times and significant cost.
7. UV Protection and Weathering
Both materials can block UV. Polycarbonate achieves this through a co-extruded UV-protective layer (30 to 50 microns thick) that prevents yellowing and degradation. Tempered glass blocks UV naturally up to a point and can be further enhanced with coatings.
The difference: polycarbonate’s UV layer is integral and permanent (co-extruded, not applied). Glass coatings can scratch, wear, or delaminate over time if not properly protected. For harsh outdoor environments—coastal salt spray, high-altitude UV, industrial pollution—polycarbonate’s inherent UV resistance often proves more durable in practice.
Decision Guide: When to Choose Which
| Scenario | Recommended Material | Reason |
|---|---|---|
| Storefront / display window | Tempered Glass | Crisp, undistorted clarity; scratch resistance |
| Greenhouse / nursery | Polycarbonate (Multiwall) | Lighter, better insulation, diffused light for plant growth |
| Safety barrier / machine guard | Polycarbonate (Solid) | 200x impact resistance; will not shatter |
| Skylight / atrium | Polycarbonate (Multiwall) | Lighter load on roof structure, better U-value |
| Pool enclosure | Polycarbonate | Humidity-resistant, hail-proof, lighter framing |
| Interior partition | Either | Glass for premium aesthetics; PC for safety and budget |
| Canopy / carport | Polycarbonate | Lightweight, hail-resistant, easy DIY installation |
| Balcony railing | Tempered Glass | Scratch resistance; premium look |
| Hurricane-prone glazing | Polycarbonate | Will not break from wind-borne debris |
| Curved architectural feature | Polycarbonate | Cold-bendable; no hot-forming required |
Common Questions About Polycarbonate vs Glass
Does polycarbonate scratch more easily than glass?
Yes. Polycarbonate is softer than glass and can be scratched by abrasive cleaners or contact with sharp objects. However, most polycarbonate sheets now come with a factory-applied hard coating that significantly improves scratch resistance. For overhead or vertical applications where physical contact is minimal, this is rarely a practical concern over the product’s lifespan.
Will polycarbonate turn yellow over time?
Modern co-extruded UV-protected polycarbonate sheets carry 10 to 15 year warranties against yellowing and loss of impact strength. The UV barrier is molecularly bonded during manufacturing—not a surface film that can peel. Proper installation (UV-protected side facing outward, drainage for condensation) is the key to long-term clarity.
Is polycarbonate fire-rated?
Yes. Most polycarbonate sheets meet B1 (GB 8624) and UL94 V-0 to V-2 fire classifications. In a fire, polycarbonate melts and shrinks away from the flame rather than shattering or producing flaming droplets, which can actually aid smoke ventilation in early-stage fires. Check local building codes for specific requirements.
Can I mix polycarbonate and glass in the same project?
Absolutely. Many commercial buildings use glass for vertical vision glazing (where people look through) and polycarbonate for overhead or backlit elements. The materials are compatible as long as thermal expansion gaps are respected for the polycarbonate sections.
Conclusion
There is no universal best glazing material—only the best material for your project. Polycarbonate excels where weight, impact resistance, insulation, and budget drive the decision. Glass remains the standard where ultimate scratch resistance and optical perfection matter most.
For the majority of overhead, safety, agricultural, and industrial glazing applications, polycarbonate delivers over 90% of the visual performance of glass at a fraction of the weight and cost—with dramatically better breakage safety.
Need help selecting the right polycarbonate sheet for your project? Contact our team for a quote.
