Mineral wool
Reference lambda value for mineral wool.
Mineral wool lambda
Lambda value mineral wool
Reference lambda value for mineral wool.
Assembly thickness
Shown as a 10 cm reference layer for comparison.
U-value
Lower lambda means better insulation performance.
| Material | Mineral wool |
|---|---|
| Category | General insulation |
| Lambda | 0.035 W/mK |
| Thickness | Shown as a 10 cm reference layer for comparison. |
Mineral wool is a core insulation reference material for many wall assemblies.
Use the material catalog to compare it against EPS, XPS, and higher-performance products.
Practical note
How to interpret lambda for Mineral wool
Mineral wool should be assessed through declared lambda, layer thickness, and the conditions it will see inside the assembly. In this database the material is grouped as “General insulation”, and the reference value is shown as Lambda 0.035 W/mK. Use it as a comparison value, not as a guarantee for every product sold under a similar name.
Real insulation performance depends on density, moisture, temperature, ageing, compression, and installation quality. Two products with similar commercial names can have different declared values, so current technical data sheets should be checked before purchase or specification.
In a simple calculation, layer resistance is thickness in metres divided by lambda. If a layer is 100 mm and lambda is 0.040 W/mK, resistance is about 2.50 m²K/W. A complete U-value still needs the other layers, surface resistances, and thermal bridge review.
Do not compare the material by lambda alone. Moisture resistance, compressive strength, fire behaviour, acoustic goals, compatibility with adhesives or membranes, and the ability to form a continuous layer can all change the best choice. For final decisions, use current manufacturer data and local requirements.
When comparing materials, check whether the value is a declared design value, a laboratory value, or a calculation value. Different sources may show different numbers for the same product family, especially when density, moisture, or application changes.
A material with a strong lambda value does not guarantee a strong U-value if it is installed too thinly or with thermal bridges. After reading the value, test the full layer build-up in the calculator.
Material selector data
These ranges feed the calculator material lists. Treat them as typical ranges and verify product declarations.
| Id | Material | R per inch | λ range | Note | Page |
|---|---|---|---|---|---|
fiberglass | Fiberglass batt | R 3.0-3.8/in | 0.038-0.046 W/mK | Lightweight option for walls and attics; verify the product declaration. | Open |
mineral-wool | Mineral wool | R 3.7-4.3/in | 0.034-0.041 W/mK | Non-combustible layer for walls, roofs, and acoustic assemblies. | Open |
eps | EPS foam | R 3.6-4.2/in | 0.034-0.040 W/mK | Rigid board for floors, walls, and exterior systems. | Open |
xps | XPS foam | R 4.5-5.0/in | 0.029-0.034 W/mK | Rigid board with good moisture and compressive resistance. | Open |
polyiso | Polyiso board | R 5.6-6.5/in | 0.020-0.026 W/mK | High R per inch at lower thickness; facers change declared values. | Open |
Assumptions and sources
Material values are typical ranges for early comparison. Real values depend on the product, density, moisture, installation, and manufacturer declaration.
- Check the product datasheet before selecting a final lambda or R per inch value.
- Local codes, thermal bridges, and air layers can change the required result.
- For permit or design work, have the assembly reviewed by a qualified professional.
- Last range review: 2026-04-27.
See how formulas, unit conversions, rounding, and limitations are handled. Methodology details.
What lambda means here
Material note
Mineral wool is a core insulation reference material for many wall assemblies.
Use case note
Use the material catalog to compare it against EPS, XPS, and higher-performance products.
Frequently Asked Questions
Lambda is the thermal conductivity of a material, usually shown in W/mK. Lower lambda means heat moves through that material more slowly, but the final assembly still depends on thickness, surface resistances, and every other layer.
U-value describes heat loss through the whole building element, not just one material. A low U-value usually means a better insulated wall, roof, or floor, provided the real build-up matches the layers entered in the calculator.
Yes. Use the comparison section to keep thickness constant, then compare materials by lambda and calculated thermal resistance. This is useful when two products look similar on paper but behave differently at the same installed depth.
Yes. You can print the result or export it to CSV, Excel, or PDF for reports and documentation.
Yes. It is designed for layered assemblies such as external walls, flat roofs, pitched roofs, floors, and slabs. For unusual assemblies, add every relevant layer and treat the result as a planning check before formal verification.
Yes. It is intended for fast concept-stage calculations, insulation comparison, and envelope optimisation before detailed design. It is best used to narrow choices, not to replace a code check or project-specific thermal bridge assessment.
Yes. You can switch between millimeters, centimeters, and inches, and the calculator keeps the values consistent. For fewer mistakes, choose one unit system at the start of a project and review converted thicknesses before export.
Use Lambda value mineral wool as a first-pass reference. Before specifying anything, compare the result with the working flow, actual project dimensions, product data sheet, and local requirements.