Warm pitched roof, Thermapitch TP10
PIR between and under the rafters to bring a loft inside the heated envelope — a room-in-roof build-up.
Layers, outside to inside
| Layer | Thickness | W/(m·K) | R |
|---|---|---|---|
| Kingspan Thermapitch TP10 | 120 mm | λD 0.022 | 5.45 |
| Kingspan Thermapitch TP10 | 50 mm | λD 0.022 | 2.27 |
| Plasterboard (generic) | 13 mm | λ 0.21 | 0.06 |
Where this fits
This is what a loft conversion needs: the insulation follows the roof slope so the space below it is heated, unlike a cold loft where the insulation sits on the ceiling. The layer under the rafters is not optional — it is what interrupts the timber, and leaving it out is the single most common way this build-up underperforms. Rafter depth usually decides the thickness available, so check the headroom that remains before specifying.
What the calculation assumes
Series calculation through continuous layers. Rafters bridge the between-rafter insulation and are NOT modelled here, so a built roof performs measurably worse than this figure — treat it as an upper bound and size the under-rafter layer generously. Surface resistances are the EN ISO 6946 defaults for this element. This is an indicative figure for comparing constructions, not a compliance calculation.
Sources
- Kingspan Thermapitch TP10 — declared data · checked 2026-08-25
Change it, or use it
Open it in the calculator to swap a layer, change a thickness or solve for a target U-value — the result keeps its own URL, so a build-up you have altered is still something you can send to someone. Or take this one straight into the editor, where it arrives as a named wall type you can assign to the walls you have drawn: the thickness follows and the U-value comes with it. Nothing is assigned until you say so.