Posted by B. Decker on 12th May 2026

Polycarbonate vs. Glass Skylights

Introduction: The Material Decision That Shapes the Entire Project

Every skylight and translucent facade starts with the same pressure point: choose the wrong glazing material and you spend the next decade managing callbacks, energy overruns, and structural workarounds. Choose the right one and the building practically runs itself.

For decades, glass was the default. It carried the aesthetic credibility architects needed, the code familiarity contractors wanted, and the optical clarity owners expected. But the calculus has shifted. Advances in polycarbonate and acrylic technology have produced materials that outperform glass on multiple critical dimensions—impact resistance, thermal efficiency, installation weight, and total cost of ownership—while closing the gap on the only area where glass once held clear dominance: pure optical transparency.

This guide is designed for architects, façade engineers, roofing contractors, and property owners who need to make that material decision with data, not assumptions. It covers polycarbonate, acrylic, and glass across every performance category that matters, including the building code context you cannot afford to overlook.

Material-by-Material Performance Breakdown

Before diving into use-case guidance, here is a direct side-by-side comparison of the three primary glazing materials across the metrics that drive specification decisions:

Performance Metric Polycarbonate Acrylic (PMMA) Glass
Light Transmission 80–92% 92–93% 83–90%
Impact Resistance 250× stronger than glass 17× stronger than glass Baseline
Weight vs. Glass ~⅛ the weight ~½ the weight Baseline
Thermal U-Value (multi-wall) 0.17–0.40 BTU/h·ft²·°F 0.50–0.60 (multi-skin) 0.48–0.80 (double IGU)
UV Protection Co-extruded cap blocks 99%+ UV Naturally UV-stable; blocks up to 98% Requires coating
Scratch Resistance Moderate (coatings available) Excellent; polishable Excellent
Longevity 10–25 years typical 20–30 years with UV-stable grades 40–50 years
Material Cost (per sq ft) $8–$12 (solid sheet) Comparable to polycarbonate $20–$30+
Installation Complexity Low — no crane, flexible framing Low High — precise framing, rigging
Fire Behavior Self-extinguishing grades available Check local jurisdiction Non-combustible

Key Takeaways from the Comparison

Transparency: Acrylic edges out polycarbonate slightly in light transmission, achieving up to 93% versus polycarbonate's 88–92%. Both materials match or exceed standard glass at 83–90%. For interiors requiring maximum natural light without artificial supplementation, acrylic is the glass-equivalent choice.

Impact Resistance: This is where polycarbonate separates itself from both competitors. At 250 times the impact resistance of glass (tested per ASTM D3763), polycarbonate is the unambiguous choice wherever falling debris, hail, vandalism, or ballistic threats are concerns. Acrylic offers 17× the impact resistance of glass—a significant improvement, but not in polycarbonate's category.

Thermal Performance: Multi-wall polycarbonate glazing (MWP) outperforms standard double-pane insulated glass units on U-value. A 25mm MWP system delivers a U-value of approximately 0.26 versus 0.48 for a comparable double-pane IGU. Advanced 50mm MWP panels achieve U-values as low as 0.17. This translates directly to HVAC cost reduction—especially meaningful for large commercial skylight arrays and translucent facade systems.

Multi-Wall Polycarbonate Glazing: The Commercial Standard

Multi-wall polycarbonate glazing (MWP) is not simply a thicker version of solid polycarbonate sheeting. Its cellular, multi-chamber cross-section creates insulating air columns that fundamentally alter thermal behavior—making it the dominant choice for large-span architectural applications.

Performance by the Numbers

  • Light transmission: Up to 82% visible light transmission depending on thickness and color selection

  • Impact resistance: A standard 8mm MWP panel withstands the impact of a 16 lb. weight dropped from 25 feet—200 times greater impact resistance than glass

  • Thermal: U-values range from 0.40 for 16mm panels to 0.17 for 50mm systems, measurably outperforming conventional double-pane glass at 0.48

  • Weight: Approximately one-eighth the weight of equivalent glass, dramatically reducing structural load requirements

  • UV protection: Co-extruded UV cap layers absorb 99%+ of harmful UV radiation without affecting light transmission

  • Span capability: 50mm MWP profiles can free-span up to 12 meters in curved facade applications with no intermediate framing

Where Multi-Wall Polycarbonate Outperforms Glass

MWP's combination of thermal performance, impact resistance, and lightweight handling makes it the superior specification in several specific conditions:

  • Large commercial skylights and barrel vault roofs where glass weight creates structural overhead

  • Industrial and manufacturing facilities where hail, UV, and impact risk is chronic

  • School and healthcare projects where safety glazing requirements and lifecycle cost both matter

  • Translucent curtain wall facades where thermal performance must integrate with daylighting strategy

  • Retrofit applications where structural support cannot accommodate glass-weight loads

Farco Plastics supplies polycarbonate sheets cut to size with fabrication support for custom architectural glazing applications. Explore Farco's polycarbonate line.

Acrylic Roofing Panels: Optimal Applications

Acrylic (polymethyl methacrylate, or PMMA) occupies a specific and well-defined niche in architectural glazing. It is not the right choice for every application—but for projects requiring the closest visual match to glass with excellent long-term clarity and natural UV stability, acrylic is the stronger specification.

Why Specify Acrylic Over Polycarbonate

  • Optical clarity: Acrylic achieves up to 93% light transmission and can be polished to restore surface clarity—polycarbonate cannot

  • Natural UV stability: Quality acrylic grades are inherently UV-stable without requiring co-extruded coatings, making them resistant to yellowing over 20–30 year service lives

  • Surface hardness: Acrylic is significantly more scratch-resistant than polycarbonate, making it preferable for surfaces that receive regular maintenance or cleaning

  • Cost efficiency: Acrylic is typically more cost-effective than polycarbonate for applications where extreme impact resistance is not required

  • UV transmission option: For greenhouse glazing and horticultural applications requiring UV transmission, UV-transmitting acrylic allows up to 92% UV ray passage—a property polycarbonate and glass do not offer

Optimal Acrylic Applications

Acrylic roofing panels excel in patio covers and sunrooms (maintaining up to 90% light transmission over 30 years), residential skylights in low-impact environments, decorative overhead glazing in retail and hospitality projects, and light diffuser systems for interior ceilings. Double-skin acrylic multi-wall systems add thermal insulation while preserving acrylic's optical advantages, making them a genuine competitor to polycarbonate MWP in moderate-climate commercial applications.

Farco Plastics offers acrylic sheets in clear, translucent, frosted (P95), and specialty grades with custom fabrication capabilities. Explore Farco's acrylic line.

When Glass Is Still the Right Choice

This guide does not make the case that glass is obsolete—it makes the case that glass should be an informed specification, not a default. Glass remains the stronger choice in specific conditions:

  • High-aesthetic commercial interiors where optical perfection and an inorganic material feel are non-negotiable to the design program

  • Floor-level glazing in premium occupied spaces where scratch resistance and longevity outweigh installation cost

  • Long-span flat skylights in temperate climates where triple-pane IGUs with argon fill can match or exceed polycarbonate thermal performance at the cost of higher structural investment

  • Fire-rated assemblies under IBC Type I and II construction where non-combustibility is required

  • Projects with 40–50 year replacement cycles where glass's longer lifespan justifies the cost premium

The critical point is that glass demands more from the structure around it—heavier framing, stronger supports, and more precise installation tolerances—while plastics offer design flexibility and safety properties that glass cannot match.

Building Code & Compliance Context

Code compliance is not a box-checking exercise—it is a risk management framework that directly affects material selection. Here is what architects and contractors must understand about skylights and facade glazing under the International Building Code (IBC) and related standards.

IBC Section 2405 – Sloped Glazing

For sloped glazing (any glazing at more than 15 degrees from vertical), IBC Section 2405 specifies permitted glazing materials. Accepted options include laminated glass with a minimum 30-mil PVB interlayer, heat-strengthened glass, fully tempered glass, and light-transmitting plastic materials meeting IBC Section 2607 criteria. Fully tempered glass used as monolithic glazing below occupied areas requires a protective screen unless an exception applies—laminated glass and code-compliant plastics do not carry this restriction.

IBC Section 2610 – Light-Transmitting Plastic Skylight Glazing

Skylight assemblies glazed with light-transmitting plastic must conform to IBC Section 2610. Key requirements include:

  • Maximum individual skylight area of 100 sq. ft. within the curb (exceptions apply for buildings with automatic sprinkler systems)

  • Minimum 4-inch curb height for skylight mounting

  • Fire-rated roof assemblies cannot be penetrated by plastic skylights unless the skylight assembly itself carries an equivalent fire rating or complies with IBC 712.1.15

  • Plastic glazing materials must be classified per ASTM standards; most architectural polycarbonate carries a CC2 classification appropriate for general skylight use

ICC-ES Listing and ESR Numbers

For projects requiring code compliance verification, architects should confirm that specified skylight assemblies carry an ICC Evaluation Service Report (ESR) number. This confirms the assembly—including its glazing material—has been evaluated against IBC performance criteria. Farco's polycarbonate and acrylic materials are available with specification data to support submittal documentation and product approval processes.

Energy Code Compliance (U-Factor & SHGC)

Beyond structural codes, skylights must comply with applicable energy codes governing U-factor and Solar Heat Gain Coefficient (SHGC). Jurisdictions such as New York City cap skylight U-factors at 0.55 BTU/h·ft²·°F under the NYCECC. Multi-wall polycarbonate systems with U-values of 0.17–0.40 comfortably meet this threshold across most climate zones. Architects should specify the full-assembly U-value (not center-of-glass only) to satisfy NFRC 100-2017 testing protocol.

Practical Selection Criteria: Questions to Ask Before Specifying

Architects and contractors asking the right questions at the front end of a project will make better material decisions. Here is a structured framework:

Structural constraints

  • What is the dead load capacity of the existing or planned roof structure? Glass weight may require structural reinforcement that MWP or solid polycarbonate does not.

Climate and impact exposure

  • Is the site in a hail-prone region, hurricane zone, or high-vandalism area? Polycarbonate's ASTM E1996-tested impact resistance makes it the only material that passes all skylight impact safety classifications including the Class 4 "hurricane test".

Thermal performance targets

  • What energy code U-factor must the skylight assembly meet? For commercial projects in climate zones 4–8, multi-wall polycarbonate delivers better-than-code performance at lower installed cost than triple-glazed glass.

Optical requirements

  • Does the project require true optical clarity (museum, retail, high-end residential)? Consider laminated glass or premium acrylic. For diffused daylighting in commercial or industrial settings, MWP's light-diffusing properties actually improve workspace uniformity over direct-transmission glass.

Service life and maintenance budget

  • Glass carries a 40–50 year lifespan; polycarbonate typically 10–25 years; acrylic up to 30 years with UV-stable grades. Factor replacement cycles into lifecycle cost analysis.

Fire and code jurisdiction

  • Confirm whether the project falls under IBC Type I or II construction (non-combustible framing required) or whether the roof assembly carries a fire-resistance rating that would preclude plastic glazing under IBC 2610.

Fabrication and installation complexity

  • For complex geometry (curved barrel vaults, faceted facades), polycarbonate's thermoformability and its ability to cold-bend without cracking gives it significant installation advantages over glass. Farco provides fabrication support—custom cutting, edge finishing, and technical specifications—for complex architectural glazing projects. Contact Farco for a custom quote.

FAQ: Polycarbonate, Acrylic & Glass Skylights

The questions below represent the most common inquiries Farco's technical team fields from architects, contractors, and property owners.

Q1: Is polycarbonate as clear as glass for skylight applications?
Polycarbonate achieves 80–92% visible light transmission depending on grade and thickness—comparable to standard window glass at 83–90%. The slight reduction in clarity is typically imperceptible in overhead skylight applications, and multi-wall polycarbonate's light-diffusing properties can improve daylight quality in large commercial interiors.

Q2: How does multi-wall polycarbonate compare to double-pane glass for insulation?
A 25mm multi-wall polycarbonate system achieves a center-pane U-value of approximately 0.26 BTU/h·ft²·°F versus 0.48 for a standard double-pane IGU of equivalent width—roughly 46% better thermal performance. Advanced 50mm MWP systems reach U-values as low as 0.17.

Q3: Will polycarbonate yellowing be a problem over time?
Standard-grade polycarbonate can yellow with UV exposure. Architectural-grade polycarbonate features a co-extruded UV cap layer that blocks 99%+ of UV radiation and prevents yellowing for the material's rated service life. Always specify UV-stabilized architectural grades for exterior applications; Farco's polycarbonate products are available in UV-stabilized formulations.

Q4: Can polycarbonate skylights meet building code requirements?
Yes. Light-transmitting plastic skylights are explicitly addressed in IBC Section 2610. Compliant polycarbonate products carry CC2 classifications and, for full code assurance, ICC-ES Evaluation Report numbers verifying IBC compliance. Energy code compliance is achieved through MWP systems' demonstrated U-factor performance under ANSI/NFRC 100 testing.

Q5: When should I specify acrylic instead of polycarbonate?
Specify acrylic when optical clarity is the top priority, when the surface will receive regular maintenance cleaning, or when long-term non-yellowing without co-extruded UV coatings is required. Acrylic's 93% light transmission and natural UV stability make it the preferred choice for aesthetic-forward residential skylights, retail canopies, and patio cover applications. Choose polycarbonate when impact resistance, thermal performance (MWP), or large-span structural flexibility is the primary driver.

Q6: How does polycarbonate perform in fire situations?
Self-extinguishing grades of polycarbonate comply with UL 94 V-2 and higher classifications. However, IBC Type I and II construction requires non-combustible framing for skylights, and plastic glazing cannot be used in fire-resistance-rated roof assemblies unless the assembly meets the same rating. Consult the Authority Having Jurisdiction (AHJ) for project-specific fire code interpretation.

Q7: What is the total cost difference between polycarbonate and glass skylights?
Material costs for polycarbonate run $8–$12 per square foot versus $20–$30+ for tempered glass. Installation labor is 30–50% lower for polycarbonate due to its lightweight handling—no crane or complex rigging required. Structural framing requirements are also reduced by 20–30% with polycarbonate. Over a 15-year TCO, polycarbonate's combined material, installation, and energy savings result in a meaningfully lower total cost despite its shorter nominal service life compared to glass.