MATERIALS & COMPOSITION GUIDE
Fiberglass Shingles: Mat Composition, Benefits & Standards
Fiberglass shingles are modern asphalt shingles constructed with an inorganic woven fiberglass mat core coated with waterproof asphalt and mineral granules. Understanding fiberglass shingle technology clarifies how modern shingles achieve Class A fire ratings and superior moisture resistance.
Key Clarification
Are all asphalt shingles fiberglass? Yes. Virtually all modern asphalt shingles manufactured in the United States today (both 3-tab and architectural) use a fiberglass reinforcement mat. Older “organic-mat” shingles (made from recycled paper and cellulose felt) were phased out in the early 2000s due to moisture absorption and curling issues.
How Fiberglass Shingles Are Manufactured
Modern fiberglass asphalt shingles consist of four engineered layers:
- Glass Fiber Mat Core: Non-woven glass fibers bonded with synthetic resins provide structural tensile strength and tear resistance.
- Asphalt Coating: Specially formulated oxidized or polymer-modified asphalt coats both sides of the mat to create a waterproof barrier.
- Ceramic-Coated Mineral Granules: Embedded on the top surface to block UV solar radiation, provide color, and add algae resistance (copper/zinc additives).
- Backing Material & Sealant Strip: Fine mineral backing prevents shingles from sticking in packaging, while a heat-activated asphalt sealant strip bonds courses together on the roof.
Fiberglass vs. Legacy Organic-Mat Shingles
| Property | Modern Fiberglass Shingles | Legacy Organic Shingles (Phased Out) |
|---|---|---|
| Core Reinforcement | Inorganic woven glass fibers | Cellulose / recycled paper felt |
| Fire Rating (ASTM E108) | Class A (Highest fire resistance) | Class C (Combustible core) |
| Moisture Absorption | Near zero moisture absorption | Prone to water absorption, swelling, and rot |
| Weight | Lightweight (~200–240 lbs/sq) | Heavy (~280–320 lbs/sq) |
| Thermal Stability | Resists curling and blistering | Curled and cracked under high attic heat |
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