BANARTA
For a flat, uniform XPS insulation layer, RSI = thickness in metres ÷ thermal conductivity (lambda). RSI is expressed in m²·K/W; US customary R-value is approximately RSI × 5.678. There is no single R-value for every XPS board: use the thickness and thermal data for the grade being quoted.
Use the XPS insulation R-value calculator to compare two candidates. A smaller lambda and a larger R-value indicate better insulation only in a like-for-like comparison. Check units and test conditions; the result for one board is not the performance of a complete floor or wall.
Three numbers that should not share one column
| Quantity | What to record | Common purchasing error |
|---|---|---|
| Lambda | W/(m·K), product grade, declared basis and conditions | Comparing values measured under different conditions |
| R-value | Thickness and either m²·K/W or US customary units | Comparing different unit systems as if equal |
| Assembly U-value | Complete construction and calculation method | Calling the board value the wall or floor value |
A supplier offering a range of thicknesses may need different declared thermal information for different products. Ask for the data applying to the actual order line rather than choosing the most attractive number in a brochure. Keep the document revision with the quotation.
A worked calculation with hypothetical inputs
For a uniform layer, R = thickness in metres ÷ lambda. If an example board is 50 mm thick and its example lambda is 0.034 W/(m·K), R = 0.050 ÷ 0.034 = approximately 1.47 m²·K/W. At 30 mm with the same assumed lambda, the result is approximately 0.88 m²·K/W.
These are teaching inputs, not Banarta product values. A quoted “R-5” in US units must not be read as 5 m²·K/W. US customary R is approximately 5.678 times the SI value; the example 1.47 m²·K/W is approximately R-8.35 in US units. Label both the unit and thickness whenever transferring a result to a purchasing sheet.
QUOTE COMPARISON
Compare two single-layer insulation values
Enter the thickness and thermal conductivity quoted for each candidate. Use the conductivity that applies to that product and thickness. Leave missing values blank.
The interactive comparison appears when the tool loads. Otherwise, use the worked calculation above: RSI = (thickness in mm ÷ 1,000) ÷ lambda; US R-value = RSI × 5.678.
Before comparing the results: check that temperatures, test or declaration basis and thickness applicability are comparable. These are separate arithmetic results from your inputs; they do not select a grade or establish whole-wall, floor or roof performance.
For one flat, homogeneous layer with parallel faces: RSI = (mm ÷ 1,000) ÷ lambda; US R-value = RSI × 5.678. Results are rounded to four significant digits. This calculation does not cover cylindrical insulation or a complete assembly.
Method references: Armacell TB01, flat homogeneous materials; NRCan, RSI conversion and nominal versus effective insulation.
Use thermal targets before comparing prices
Ask the project designer for the required layer or assembly performance. Then compare the proposed thickness and grade against that requirement. Do not replace the specified material with a thinner board solely because the supplier quotes a lower lambda. Check available space, load requirements, moisture conditions and any facing separately.
A calculation for the insulation layer omits junctions, fixings, other layers and the effects of the actual assembly. It is useful for checking a quotation, but it does not establish regulatory compliance or the complete building U-value. Refer the assembled design to the person responsible for that calculation.
Match the thermal requirement to a purchasable board
Begin with the uncoated XPS board option and identify the exact thickness and grade to be quoted. Ask for the thermal document covering that configuration, rather than treating the product's full size range as one thermal specification. If the board supports a floor, also review compression and long-term creep evidence.
Request a specification and quote: include the designer's thermal target and units, available thickness, application, quantity and destination. Mark any missing target as awaiting design confirmation.
Copy these fields into a comparison sheet
- Supplier, exact product name and grade.
- Nominal thickness and the thermal value applicable to that thickness.
- Value, units, test or declaration basis and document date.
- Declared versus design value, with any adjustments identified.
- Separate evidence for compression, moisture exposure and intended use.
- Price per board and usable square metre for the same approved specification.
If one offer omits the test basis, mark it “not yet comparable” instead of assigning it a better or worse thermal ranking. Ask for the missing field before ordering. Save the accepted document with the purchase order so a later substitution can be checked against the same baseline.
Request the right XPS specification
Browse Banarta XPS insulation boards and use the thickness and strength selection guide for the wider decision. Send the target performance, thickness allowance, quantity and destination through the enquiry page.
Reference and scope
DuPont Square Edge product information illustrates how a manufacturer identifies thickness and R-value together. Its figures apply to its named products, not Banarta. Obtain the current specification for the Banarta grade being quoted.
