Cork Insulation

Material Type

Tree-Bark Renewable Thermal Insulation

Material Description

Cork insulation is the same renewable cork bark used for flooring and wine stoppers, expanded and bonded into rigid insulation board with no added binders — the suberin in the cork bark itself acts as the natural binder under steam heat. The cellular structure is ~50% air by volume, giving R-3.6 to R-4.0 per inch. Cork is naturally antimicrobial via its suberin content, fire-resistant (it chars rather than burns), water-shedding, and biodegradable at end of life. EBH specifies cork for exterior continuous insulation where vapor-open performance matters, and as acoustic underlayment.

Composition & Origin

Expanded cork agglomerate · suberin self-binds under steam · ~120 kg/m³ density · R-3.6 to R-4.0 per inch

Health Profile — All Endpoints Clear

Severity scored 0–10 against the same 10 hazard endpoints we use for the chemical families on the avoid list. Every score is 1–2 — essentially no signal across every endpoint.

Common Forms & Brands

• ThermaCork rigid insulation board
• Amorim Insulation Cork Board
• Aerocork loose-fill cork
• Common framing: rigid exterior continuous insulation board, acoustic underlayment, loose-fill

Why We Use It

• Renewable — harvested without cutting the cork oak
• Self-binding via suberin — no added formaldehyde or isocyanate adhesive
• Naturally antimicrobial and mold-resistant
• Fire-char layer slows combustion
• Carbon-negative life cycle

Where It Performs Best

• Exterior continuous insulation on walls and roofs
• Below-grade insulation (water-tolerant)
• Acoustic underlayment beneath finished floors
• Sub-slab thermal break

Building Applications for Cork Insulation

Listed alphabetically. Where in a home this material earns its keep.

• Below-Grade Foundation Insulation
• Exterior Continuous Wall Insulation
• Floor Acoustic Underlayment
• Roof Sheathing Insulation
• Sub-Slab Insulation Layer