Estimating & compliance calculator
Insulation Calculator
Calculate insulation quantities and check the resulting U-value against Part L reference limits - a construction cross-section diagram, layer by layer, not just a number.
Estimating & compliance calculator
Calculate insulation quantities and check the resulting U-value against Part L reference limits - a construction cross-section diagram, layer by layer, not just a number.
The build-up is drawn as a stacked band viewed edge-on - each layer a proportionally-wide coloured segment scaled to its real physical thickness, labelled with material, thickness and thermal conductivity.
Each layer's resistance (thickness ÷ thermal conductivity) is summed with fixed surface resistances for the element type, then compared against a Part L reference target with a clear pass/fail badge.
Pitched roof (loft insulation), flat roof, external wall and ground floor - each with its own Part L reference target U-value and surface resistances.
Mineral wool, PIR/PUR board, wood fibre, plasterboard, brick, blockwork, dense concrete, timber, OSB/plywood and a fixed-resistance air gap - each with a typical thermal conductivity you can still edit.
Enter the area to cover and a cost per m³, and get the insulation volume needed and an estimated materials cost - driven straight from your layer build-up.
Every material preset's thermal conductivity, and every element type's target U-value, in one searchable lookup table - for planning without leaving the app.
Copy a plain-text summary of the build-up and result to the clipboard, or export a standalone HTML file to keep or share.
Light/dark theme remembers your choice, and two rotating sample build-ups - a loft top-up and a cavity wall with PIR board - let you explore the app before entering your own job.
Kingspan's free online U-value calculator is a well-known tool UK contractors reach for on site. It's free to use but built around Kingspan's own product range - here's how a manufacturer-neutral, offline desktop tool compares.
| Feature | Insulation Calculator | Kingspan U-value Calculator |
|---|---|---|
| Pricing model | One-off purchase after a free trial | Free (web tool, no account needed) |
| Works fully offline | ✓ | ✕ |
| Manufacturer-neutral (any material, not one brand) | ✓ | ✕ |
| Condensation risk analysis | ✕ | ✓ |
| Cost estimate for insulation quantity | ✓ | ✕ |
| Searchable material reference tab | ✓ | ✕ |
| Ten presets across four element types, worldwide use | ✓ | ~ |
| BBA/TIMSA-recognised competency-scheme calculation | ✕ | ✓ |
Comparison based on Kingspan's publicly listed features as of August 2026 (insulation.kingspan.com, buildingcentre.co.uk, procalculator.co.uk) - features change over time, so check insulation.kingspan.com for current details. Kingspan is a trademark of its respective owner; this comparison is for informational purposes and isn't sponsored by or affiliated with Kingspan.
Build up a wall, roof or floor from layers, see the cross-section, and check the U-value against a Part L reference target.
The cross-section diagram and the U-value result, checked against the Part L reference target
A quick-lookup reference of material presets and target U-values by element type
Insulation Calculator is a Windows desktop app, free to try from the Microsoft Store.
Yes - Insulation Calculator uses the same shared Metre2 account as Vector, Forma and every other Keystone app. Sign in once and it works everywhere.
Each layer's thermal resistance is R = thickness in metres divided by its thermal conductivity (lambda). Those are summed with the element type's fixed internal and external surface resistances (Rsi/Rso) to get a total resistance, then U = 1 divided by that total.
No - the target U-values are commonly-cited approximate Part L reference figures for new work/renovation, illustrative planning figures rather than a certified compliance tool. Always check the current Building Regulations edition that applies to your job, or get a proper SAP/RdSAP assessment, before relying on this for sign-off.
The actual layer build-up, drawn as a stacked band viewed edge-on - each layer a proportionally-wide coloured segment scaled to its real physical thickness, labelled with material, thickness and lambda, so you can see the construction as well as calculate it.
The app sums the thickness of every layer flagged as an insulation material, multiplies by the area you enter to get a volume, and multiplies that by your editable cost-per-m³ figure for an estimated materials cost.
Yes - copy a plain-text summary to your clipboard, or export a standalone HTML file with the full build-up and result.