UK product data · 31 documented thickness rows
Kingspan U-value calculator
Model a layered assembly with Kingspan Thermapitch TP10 or Kooltherm K108 selected from current UK product literature. The two products serve different applications, so this page keeps their roof and cavity-wall context visible instead of treating them as substitutes.
Element surfaces and correction
The element label sets only the displayed surface-resistance pair. An exposed floor is not a ground-coupled floor calculation. Use Custom when the boundary conditions differ.
Assembly result
Effective R m²K/W
Layer R before bridge correction · m²K/W
Illustrative starting layers, not an approved specification. One repeating timber layer only. No metal frames, ground-coupled floors or automatic fixing/gap corrections. A U-value alone does not establish compliance.
Saved comparisons
| Assembly | U (W/m²K) | Actions |
|---|
Calculation ledger
| Layer | Thickness (mm) | λ (W/mK) | Calculated R (m²K/W) | Declared R (m²K/W) |
|---|
Fixed R has no implied thickness or conductivity. All intermediate calculations retain full precision; display values are rounded.
Source-linked comparison
Kingspan product data
Use TP10 rows when checking a pitched-roof insulation layer and K108 rows when checking a partial-fill cavity-board layer. The calculator combines the selected product layer with any other layers you enter; it does not approve the resulting construction.
Checked · Version 2026-08-29.1 · Selected UK product literature, not live stock or a complete manufacturer catalogue.
What the dataset lets you decide
- Thermapitch TP10: 16 documented thicknesses from 25 to 150 mm, with declared conductivity 0.022 W/mK.
- Kooltherm K108: 15 documented thicknesses from 25 to 150 mm, with declared conductivity 0.019 W/mK.
- Declared R and calculated thickness/λ are both retained so rounding remains visible.
Manufacturer property facts remain attributed to their linked sources. Inzonex supplies the selection, calculation, chart and reusable exports.
All 31 source-linked rows
| Product | Documented use | mm | λ (W/mK) | Declared R | Calculated R | References |
|---|---|---|---|---|---|---|
| Kingspan Thermapitch TP10 | Pitched roof | 25 | 0.022 | 1.10 | 1.136 | Property · range/use |
| Kingspan Thermapitch TP10 | Pitched roof | 30 | 0.022 | 1.35 | 1.364 | Property · range/use |
| Kingspan Thermapitch TP10 | Pitched roof | 40 | 0.022 | 1.80 | 1.818 | Property · range/use |
| Kingspan Thermapitch TP10 | Pitched roof | 50 | 0.022 | 2.25 | 2.273 | Property · range/use |
| Kingspan Thermapitch TP10 | Pitched roof | 60 | 0.022 | 2.70 | 2.727 | Property · range/use |
| Kingspan Thermapitch TP10 | Pitched roof | 70 | 0.022 | 3.15 | 3.182 | Property · range/use |
| Kingspan Thermapitch TP10 | Pitched roof | 75 | 0.022 | 3.40 | 3.409 | Property · range/use |
| Kingspan Thermapitch TP10 | Pitched roof | 80 | 0.022 | 3.60 | 3.636 | Property · range/use |
| Kingspan Thermapitch TP10 | Pitched roof | 90 | 0.022 | 4.05 | 4.091 | Property · range/use |
| Kingspan Thermapitch TP10 | Pitched roof | 100 | 0.022 | 4.50 | 4.545 | Property · range/use |
| Kingspan Thermapitch TP10 | Pitched roof | 110 | 0.022 | 5.00 | 5.000 | Property · range/use |
| Kingspan Thermapitch TP10 | Pitched roof | 120 | 0.022 | 5.45 | 5.455 | Property · range/use |
| Kingspan Thermapitch TP10 | Pitched roof | 125 | 0.022 | 5.65 | 5.682 | Property · range/use |
| Kingspan Thermapitch TP10 | Pitched roof | 130 | 0.022 | 5.90 | 5.909 | Property · range/use |
| Kingspan Thermapitch TP10 | Pitched roof | 140 | 0.022 | 6.35 | 6.364 | Property · range/use |
| Kingspan Thermapitch TP10 | Pitched roof | 150 | 0.022 | 6.80 | 6.818 | Property · range/use |
| Kingspan Kooltherm K108 | Partial-fill cavity wall | 25 | 0.019 | 1.30 | 1.316 | Property · range/use |
| Kingspan Kooltherm K108 | Partial-fill cavity wall | 30 | 0.019 | 1.55 | 1.579 | Property · range/use |
| Kingspan Kooltherm K108 | Partial-fill cavity wall | 40 | 0.019 | 2.10 | 2.105 | Property · range/use |
| Kingspan Kooltherm K108 | Partial-fill cavity wall | 50 | 0.019 | 2.60 | 2.632 | Property · range/use |
| Kingspan Kooltherm K108 | Partial-fill cavity wall | 60 | 0.019 | 3.15 | 3.158 | Property · range/use |
| Kingspan Kooltherm K108 | Partial-fill cavity wall | 70 | 0.019 | 3.65 | 3.684 | Property · range/use |
| Kingspan Kooltherm K108 | Partial-fill cavity wall | 75 | 0.019 | 3.90 | 3.947 | Property · range/use |
| Kingspan Kooltherm K108 | Partial-fill cavity wall | 80 | 0.019 | 4.20 | 4.211 | Property · range/use |
| Kingspan Kooltherm K108 | Partial-fill cavity wall | 90 | 0.019 | 4.70 | 4.737 | Property · range/use |
| Kingspan Kooltherm K108 | Partial-fill cavity wall | 100 | 0.019 | 5.25 | 5.263 | Property · range/use |
| Kingspan Kooltherm K108 | Partial-fill cavity wall | 110 | 0.019 | 5.75 | 5.789 | Property · range/use |
| Kingspan Kooltherm K108 | Partial-fill cavity wall | 120 | 0.019 | 6.30 | 6.316 | Property · range/use |
| Kingspan Kooltherm K108 | Partial-fill cavity wall | 130 | 0.019 | 6.80 | 6.842 | Property · range/use |
| Kingspan Kooltherm K108 | Partial-fill cavity wall | 140 | 0.019 | 7.35 | 7.368 | Property · range/use |
| Kingspan Kooltherm K108 | Partial-fill cavity wall | 150 | 0.019 | 7.85 | 7.895 | Property · range/use |
U-value, without hidden layers
1. Resistance in series
R_total = Rsi + ΣR_layer + Rse
U = 1 / R_total + ΔU
Thickness is entered in millimetres and converted to metres. A known-R layer accepts a separately established resistance, not a guessed cavity thickness. Surface presets use 0.10, 0.13 or 0.17 inside and 0.04 outside for the identified exposed-air cases. Other conditions need appropriate inputs.
The browser calculation is checked against the open-source ht plane-conduction reference. This is a building-layer calculation, separate from the industrial pipe tool's lumped heat-transfer coefficient.
2. One repeating timber bridge
R_lower = Rsi + ΣR_equivalent + Rse
R_effective = (R_upper + R_lower) / 2
The timber fraction is the fraction of this layer's area occupied by timber, not the fraction of the whole building. For the bridged layer, R_equivalent = 1 / [(1−f)/R_layer + f/R_bridge]. The tool stops above an upper/lower ratio of 1.5. It does not model metal framing, crossing bridges or junction ψ-values.
Both worked presets reproduce SEAI's Irish roof examples. The rafter case has R limits about 6.36 / 5.78; the ceiling case about 6.438 / 6.221, with an explicit 0.0014 W/m²K loft-hatch correction. These are examples, not UK regulatory defaults.
What this result does not decide
Actual moisture, temperature, workmanship, fixings, ventilation and junctions can change performance. This tool does not select a regulatory target, assess condensation or fire safety, verify a product's application or predict annual bills. Ground-coupled and suspended ground-floor calculations require their own geometry and boundary methods. The outside surface setting is editable because sheltered and ventilated conditions differ.
Sources and method references
- Kingspan Thermapitch TP10 GB brochure, page 5
- SOPRATHERM GA4000 technical data sheet TDS-UK-INSUK0025.a/EN
- Soprema: GA4000, previously Celotex
- ROCKWOOL Flexi technical sheet, November 2025, page 3
- ROCKWOOL Flexi UK listed product variants
- Kingspan Kooltherm K108 UK Declaration of Performance 1000.UKDoP.K108.003
- Kingspan Kooltherm K108 Cavity Board UK product page
- Recticel Eurowall+ UK technical datasheet 6VICBX7DDFHZ 230703
- Recticel Eurowall+ UK product specifications
- SEAI DEAP guidance, pages 76-79: worked roof examples
- UK government moisture research, modelling surfaces, page 12
- Santos et al., Energies 2020, section 2.1.1: combined method and limits
- ht conduction library: k_to_R
Kingspan U-value questions
Does this calculator use official Kingspan product values?
It uses thickness, declared conductivity and declared R rows transcribed from the linked UK Thermapitch TP10 brochure and Kooltherm K108 Declaration of Performance. The source links and checked date are visible in the dataset.
Should I choose TP10 or K108?
TP10 is represented with its pitched-roof context. K108 is represented with its partial-fill cavity-wall context. They have different documented applications and thermal conductivity, so the page does not present them as interchangeable boards.
Can I compare two Kingspan thicknesses?
Yes. Load either worked product-layer example, change the thickness, save the comparison, then load the other product or thickness. Up to four comparisons can be kept in the open page and exported as JSON or CSV.
Is this a Kingspan-approved U-value calculation?
No. Inzonex is not affiliated with or endorsed by Kingspan. This transparent layer calculator does not model every junction, fixing, air gap, moisture condition or regulatory requirement and is not a compliance certificate.