A bare 215mm solid brick wall has a U-value of roughly 1.6–1.7 W/m²K. Lining it internally with 60mm PIR brings it to about 0.31 — just at the 0.30 renovation target — and 80mm reaches a comfortable 0.24. Internal insulation moves the dew point, so run the free condensation check before you fix a spec.
Every layer editable · live U-value · Part L & Future Homes Standard targets · free PDF report
The build-up (outside → inside)
- 215mm solid brick
- 60–80mm PIR insulated lining
- Plasterboard
Typical U-values for this construction
| Specification | U-value (W/m²K) | Notes |
|---|---|---|
| Bare 215mm solid brick | ≈ 1.6–1.7 | The starting point |
| + 60mm PIR lining | ≈ 0.31 | Scrapes the 0.30 renovation target |
| + 80mm PIR lining | ≈ 0.24 | Comfortable pass, usual practice |
Figures computed with the BS EN ISO 6946 combined method (bridging included) using BR 443 conventional lambda values — indicative for the generic build-up shown. Your products, thicknesses and (for floors) footprint will move the number: that's what the calculator is for.
What changes the number
Thickness versus lost room is the trade. The bigger risk is moisture: cold brickwork behind new insulation is exactly where interstitial condensation shows up, which is why U-Monkey’s built-in ISO 13788 screening check matters most on this wall. Airtight detailing at joists and reveals decides whether theory survives site.
Next: check the junctions
A U-value covers the flat area of an element — but heat also escapes where elements meet, and at modern U-values those junctions can be 20–30% of a dwelling's fabric heat loss. Now you know your U-values, model the junctions with the free ΨMonkey psi value calculator (no subscription; PDF reports £25 +VAT):
Or read thermal bridging explained to see how junction Ψ-values feed your SAP calculation.
Frequently asked questions
What is the U-value of a solid brick wall with internal insulation?
A bare 215mm solid brick wall has a U-value of roughly 1.6–1.7 W/m²K. Lining it internally with 60mm PIR brings it to about 0.31 — just at the 0.30 renovation target — and 80mm reaches a comfortable 0.24. Internal insulation moves the dew point, so run the free condensation check before you fix a spec.
Is internal wall insulation risky for condensation?
It can be — insulation makes the brick colder, so vapour reaching it may condense. The screening check built into U-Monkey (ISO 13788, free) flags whether your build-up needs a vapour control layer or a different insulant. For unusual or historic walls, get a full hygrothermal assessment.
Is this calculator free?
Yes — building the element, reading the U-value, the compliance targets (including the Future Homes Standard) and the condensation-risk screening check are all free in your browser, and the Building Control-ready PDF report is free too. No sign-up.
Does it follow the official calculation method?
Yes — the combined method of BS EN ISO 6946:2017 with BR 443 conventions, including timber bridging and air-gap corrections, ISO 13370 for ground and suspended floors, and ISO 13788 for the condensation screening check.
Other common build-ups
- U-value of a cavity wall with full-fill insulation
- U-value of a cavity wall with PIR partial-fill insulation
- U-value of a timber frame wall
- U-value of a solid wall with external insulation
- What is the U-value of an uninsulated cavity wall?
- U-value of 270mm loft insulation
- U-value of insulation between rafters (loft conversion)
- U-value of a warm flat roof
- How much insulation does a flat roof need?
- U-value of an insulated concrete ground floor
- U-value of an insulated suspended timber floor
- U-value of a beam and block floor with PIR
Different build-up? See the full wall U-value calculator, or start from scratch in the main U-value calculator.
Need the wider compliance picture? U-values feed straight into SAP calculations — or let our New Build Compliance Pack handle the lot. Background reading: what U-values actually are.