Polycarbonate vs. Fiberglass
When daylighting matters and durability counts, polycarbonate outperforms fiberglass across the board. From clarity and strength to long-term performance, polycarbonate delivers. Meanwhile, fiberglass—once a low-cost option—too often ends in costly failures and premature replacement.
A Comparison Architects Can Rely On
Fiberglass: The Dollar-Store Solution Falling Apart
- Fiber Bloom & Yellowing: Over time, embedded glass fibers emerge and trap dirt (known as “fiber bloom”), reducing transmittance and making panels look dreary. Light transmission in fiberglass panels typically starts around 30–35%, then plummets within a few years (source).
- Delamination Examples: In projects like Clayton High School, original fiberglass skylights delaminated in under a decade, yellowing dramatically and losing almost all daylight function (source).
Polycarbonate: The Engineered Upgrade
- Clarity & Light Transmission: Transparent polycarbonate provides up to 90% light transmission, while more diffuse options still outperform fiberglass with 45–85% (source).
- Impact Resistance: Polycarbonate is certified to resist hail and heavy debris impacts—4× stronger than fiberglass and over 200× stronger than glass (source).
- Dimensional Precision: Polycarbonate extrusions are engineered with tight tolerances to match metal profiles and prevent leaks—fiberglass alternatives cannot (source).
- Thermal Benefits: Multi-wall polycarbonate provides improved insulation (R‑values up to 4) and solar control versus fiberglass, aiding energy efficiency and code compliance (source).
- UV Stability and Warranties: Modern polycarbonate uses UV-stable cap layers to resist yellowing for years. Many manufacturers offer 10-year light-transmission guarantees (source).
Case Studies: When Fiberglass Failed, Polycarbonate ReplacedA Canadian high school project replaced aging fiberglass skylights after only 9–10 years due to delamination and yellowing. Multi-wall polycarbonate systems were selected for their clarity, impact resistance, and ease of installation (source)
In a five-year controlled industrial study, panels made from polycarbonate maintained illumination levels (~450 lux), while fiberglass panels lost 66% of their light output, forcing the use of artificial lighting mid-day (source). These replacements underscore a proven truth: fiberglass may be cheaper—at first—but becomes costlier in lifecycle, performance decline, and client dissatisfaction.
Side-by-Side Selection Table
| Attribute | Polycarbonate | Fiberglass (FRP) |
|---|---|---|
| Light Transmission | 60–90%, diffuses light evenly | Starts 30–35%, drops fast with age |
| UV Resistance | UV-stable cap layers prevent yellowing | Prone to yellowing, fiber bloom, chalking |
| Impact Resistance | Extremely durable: 4× fiberglass, 200× glass | Brittle: liable to crack under pressure |
| Thermal Performance | Solid R-values, diffusive daylight, reduces HVAC load | Minimal insulation unless thick and costly |
| Clarity & Aesthetics | Near glass-level clarity; retains appearance over time | Hazy, opaque, discolored after a few years |
| Fabrication & Install | Easily cut, bent, and field-fabricated | Difficult to shape, needs specialized tooling |
| Lifecycle & Warranty | 15–25 years; up to 10-year warranty on clarity | 5–15 years typical; rarely guaranteed |
| Cost (Install Lifecycle) | Higher upfront, stronger lifecycle value | Cheaper early cost but higher replacement needs |
Key Benefits for Architects
- Design Flexibility: Use in curved roofs, large spans, and precision profiles without sacrificing performance.
- Low Maintenance: Wipes clean; resists mold, yellowing, fiber bloom.
- Code-Friendly: Meets OSHA, NFPA, NAFS and hurricane region wind-borne debris standards.
- Sustainable: Thermoplastic and recyclable; lightweight reduces structural impact and shipping emissions.
Final Verdict: Polycarbonate Is the Clear Winner
If durability, clarity, safety, and long-term reliability matter to your project, polycarbonate is the superior glazing. Fiberglass may tempt with lower upfront costs, but its known failure modes—including yellowing, reduced daylighting, and poor impact performance—make it
obsolete. Every time you specify fiberglass today, you’re betting against time. Give your clients a lasting daylight solution instead.
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