Partial-fill cavity wall, Kooltherm K106
Brick, a 90 mm phenolic board held against the inner leaf with a clear residual cavity, blockwork and plaster.
Layers, outside to inside
| Layer | Thickness | W/(m·K) | R |
|---|---|---|---|
| Brick (generic) | 102 mm | λ 0.77 | 0.13 |
| Air cavity (unventilated) (generic) | 50 mm | R 0.18 fixed | 0.18 |
| Kingspan Kooltherm K106 | 90 mm | λD 0.019 | 4.74 |
| Aerated concrete block (generic) | 100 mm | λ 0.16 | 0.63 |
| Plaster (gypsum) (generic) | 13 mm | λ 0.51 | 0.03 |
Where this fits
Where a full fill is unwanted — exposed sites, or a specification that insists on a clear cavity — a rigid phenolic board gets the same performance from less thickness than mineral wool, at a higher price per square metre. The residual cavity must stay genuinely clear and the boards must be tight to the inner leaf; a gap behind the board lets air loop around the insulation and quietly undoes it. K106's declared 0.019 W/(m·K) is the lowest conductivity in this catalogue.
What the calculation assumes
Series calculation through continuous layers, with the residual cavity taken as an unventilated airspace at a fixed resistance. Ties and board joints are not modelled. 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 Kooltherm K106 — 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.