Mineral wool insulation has an R-value of approximately R-4 per inch. PowerWool rigid boards are R-4.0 to R-4.2 per inch depending on the product. This table covers every mineral wool SKU Warehoos stocks, with R-value, thickness, density, and the ASTM standard used to verify the value.
R-values below are tested per ASTM C518 (steady-state thermal transmission) at 75°F mean temperature, which is the standard reference for building envelope specifications.
Mineral wool R-value reference table
| Product | R-value (per inch) | Common thicknesses | R-value (total) | Density | Standard |
|---|---|---|---|---|---|
| PowerWool RigiBoard 80 | R-4.2 | 1" / 1.5" / 2" / 2.5" / 3" / 4" / 5" (up to 8" on request) | R-4.2 / R-6.3 / R-8.4 / R-10.5 / R-12.6 / R-16.8 / R-21.0 | 8 lb/ft³ | ASTM C518 |
| PowerWool RigiBoard PRO MAX | R-4.0 | 1" / 1.5" / 2" / 2.5" / 3" / 4" / 5" | R-4.0 / R-6.0 / R-8.0 / R-10.0 / R-12.0 / R-16.0 / R-20.0 | 11 lb/ft³ | ASTM C518 |
| Rockwool Comfortboard 80 | See ROCKWOOL data sheet | 1.25" / 1.5" / 2" / 2.5" / 3" | See ROCKWOOL data sheet | See ROCKWOOL data sheet | ASTM C518 |
| Rockwool Comfortboard 110 | See ROCKWOOL data sheet | 1.5" / 2" / 3" | See ROCKWOOL data sheet | See ROCKWOOL data sheet | ASTM C518 |
| Rockwool Comfortbatt R-15 | See ROCKWOOL data sheet | 3.5" (2×4 cavity) | See ROCKWOOL data sheet | See ROCKWOOL data sheet | ASTM C518 |
| Rockwool Comfortbatt R-23 | See ROCKWOOL data sheet | 5.5" (2×6 cavity) | See ROCKWOOL data sheet | See ROCKWOOL data sheet | ASTM C518 |
Quick R-value by thickness (PowerWool rigid boards)
| Thickness | PowerWool RigiBoard 80 | PowerWool RigiBoard PRO MAX |
|---|---|---|
| 1" | R-4.2 | R-4.0 |
| 1.5" | R-6.3 | R-6.0 |
| 2" | R-8.4 | R-8.0 |
| 2.5" | R-10.5 | R-10.0 |
| 3" | R-12.6 | R-12.0 |
| 4" | R-16.8 | R-16.0 |
| 5" | R-21.0 | R-20.0 |
Nominal = thickness × R per inch. The PowerWool data sheet notes thermal values may decrease up to 1% per inch of thickness.
For ROCKWOOL Comfortboard R-values by thickness, see ROCKWOOL's current data sheet.
Available sizes: PowerWool RigiBoard 80 and RigiBoard PRO MAX
All boards are 2' × 4', sold by the bag. Both products come in these seven thicknesses online:
| Thickness | Boards per bag | Coverage per bag |
|---|---|---|
| 1" | 8 | 64 sq ft |
| 1.5" | 6 | 48 sq ft |
| 2" | 5 | 40 sq ft |
| 2.5" | 4 | 32 sq ft |
| 3" | 3 | 24 sq ft |
| 4" | 2 | 16 sq ft |
| 5" | 2 | 16 sq ft |
RigiBoard 80 is now also made in thicker boards, up to 8". For thicknesses over 5", email sales@warehoos.com or call 1-877-383-2671.
R-value vs. fire rating vs. compressive strength
R-value is one of three properties to match against your spec. PowerWool's property profile:
| Property | PowerWool RigiBoard 80 | PowerWool RigiBoard PRO MAX |
|---|---|---|
| R-value per inch (ASTM C518) | R-4.2 | R-4.0 |
| Density | 8 lb/ft³ | 11 lb/ft³ |
| Flame Spread Index (ASTM E84) | 0 | 0 |
| Smoke Developed Index (ASTM E84) | 0 | 0 |
| Non-combustible per ASTM E136 | ✓ | ✓ |
| Compressive strength @ 10% (ASTM C165) | 616 psf | 755 psf |
| Water absorption (ASTM C209) | See data sheet | 0.09% by volume |
| Vapour permeance (ASTM E96) | 35.6 perm at 1.5" | 35.6 perm at 1.5" |
For ROCKWOOL Comfortboard properties, see ROCKWOOL's current data sheet.
Choose by R-value AND application:
- Exterior continuous insulation (most common) — PowerWool RigiBoard 80 or Comfortboard 80
- Exterior walls that need higher compressive strength (commercial assemblies) — PowerWool RigiBoard PRO MAX
- Cavity insulation in framed walls — Comfortbatt R-15 (2×4) or R-23 (2×6)
IECC requirements for continuous insulation
IECC 2021 and 2024, Table R402.1.3 (residential), wood-framed walls:
| Climate Zone | Wood-frame wall options | Mineral wool thickness for the continuous insulation (ci) |
|---|---|---|
| Zones 4–8 | R-30 cavity, or R-20 cavity + R-5 ci, or R-13 cavity + R-10 ci, or R-20 ci | R-5 ci ≈ 1.5" RigiBoard 80 · R-10 ci ≈ 3" · R-20 ci ≈ 5" (nominal: confirm the labelled R-value meets R-20) |
For zones 0–3, see Table R402.1.3 in the edition your jurisdiction adopted. Always verify against your jurisdiction's adopted code edition — adoption lags the model code by 1–3 years in most jurisdictions.
Frequently asked questions
Q: What is the R-value of 2 inch mineral wool insulation?
A: PowerWool RigiBoard 80 at 2 inches is R-8.4. PowerWool RigiBoard PRO MAX at 2 inches is R-8.0. For ROCKWOOL Comfortboard, see ROCKWOOL's current data sheet.
Q: What is the R-value of 1 inch mineral wool insulation?
A: Rigid mineral wool is about R-4 per inch. PowerWool RigiBoard 80 is R-4.2 and RigiBoard PRO MAX is R-4.0 (ASTM C518, PowerWool data sheets). For Comfortboard, see ROCKWOOL's current data sheet.
Q: What is the R-value of 3 inch mineral wool insulation?
A: PowerWool RigiBoard 80 at 3 inches is R-12.6. RigiBoard PRO MAX at 3 inches is R-12.0. For ROCKWOOL Comfortboard, see ROCKWOOL's current data sheet.
Q: What is the R-value of 4 inch mineral wool insulation?
A: PowerWool RigiBoard 80 at 4 inches is R-16.8. RigiBoard PRO MAX at 4 inches is R-16.0. For ROCKWOOL Comfortboard, see ROCKWOOL's current data sheet.
Q: Does mineral wool R-value degrade over time?
A: No. Mineral wool maintains its R-value over its service life. Unlike some closed-cell foams, mineral wool does not contain blowing agents that diffuse out and reduce R-value. The PowerWool data sheet lists its tested values; follow the manufacturer's installation guidance.
Q: How does mineral wool R-value compare to fiberglass and rigid foam?
A: Mineral wool is approximately R-4 per inch. Fiberglass and rigid foam R-values vary by product and density, so compare each manufacturer's current data sheet. Mineral wool adds non-combustibility (ASTM E136) and a vapour-open, drainable layer.
Q: What R-value do I need for exterior continuous insulation in climate zone 5?
A: IECC 2021 and 2024 do not require one fixed continuous insulation value in zone 5. Wood-framed walls can use R-20 cavity + R-5 ci, R-13 cavity + R-10 ci, R-20 ci alone, or R-30 cavity only (Table R402.1.3). 1.5" of RigiBoard 80 gives R-6.3 ci. Always verify against your jurisdiction's adopted code edition.
Q: Is the R-value tested at the same temperature for all mineral wool brands?
A: Published R-values for building insulation are reported at 75°F mean temperature, using test methods such as ASTM C518. Some manufacturers also report R-value at 40°F mean (R-value rises slightly at lower temperatures). When comparing brands, confirm the test temperature is the same.
Q: Where can I see the official R-value certification for the mineral wool Warehoos sells?
A: PowerWool data sheets are linked from the PowerWool product pages. For ROCKWOOL data sheets, see ROCKWOOL or email sales@warehoos.com.
Need mineral wool insulation with verified R-values?
- Shop mineral wool insulation →
- For climate-zone-specific specs: contact sales@warehoos.com
- US contractor pricing line: 1-877-383-2671
- See our USA cross-border shipping details →
Related guides
- Continuous insulation requirements for climate zone 6 — R-value paths and code-compliant assemblies for IECC zone 6.
- Passive house exterior wall assemblies with mineral wool — Envelope build-ups, airtightness layers, and the SKUs that spec into them.
- Order mineral wool insulation online in the USA — Ships to all 50 states. Stock, thicknesses, and bulk/contractor pricing.
Disclaimer: The information on this page is taken from each manufacturer's published data and/or open source information online, and is provided for general guidance only. Specifications can change and can vary by product, thickness and market. Always confirm performance values, code compliance and suitability for your assembly against the manufacturer's current data sheet before specifying or ordering. All trademarks are the property of their respective owners.