A bare 215mm solid brick wall has a U-value of roughly 2.1 W/m²K. Lining it internally with 60mm PIR brings it to about 0.32, just short of the 0.30 renovation target; 70mm clears it at 0.28, and 80mm reaches a comfortable 0.25. 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 | ≈ 2.1 | The starting point |
| + 60mm PIR lining | ≈ 0.32 | Just short of the 0.30 renovation target |
| + 70mm PIR lining | ≈ 0.28 | Clears the 0.30 target |
| + 80mm PIR lining | ≈ 0.25 | Comfortable pass, usual practice |
Figures computed with the BS EN ISO 6946 combined method and BR 443 conventions — bridging, mortar joints in blockwork and the air-gap correction included — exactly as the pre-filled calculator works them out, with any pass or fail judged on the unrounded U-value. Indicative for the generic build-up shown: your products, thicknesses and (for floors) footprint will move the number, and 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 a junction):
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 2.1 W/m²K. Lining it internally with 60mm PIR brings it to about 0.32, just short of the 0.30 renovation target; 70mm clears it at 0.28, and 80mm reaches a comfortable 0.25. 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), the condensation-risk screening check and the thermal-mass figures (decrement factor, time lag, κ) 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, mortar joints in blockwork 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 one-and-a-half-brick (317.5mm) solid 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
- Flat roof insulation thickness — about 150mm PIR for 0.15, 140mm for 0.16
- U-value of a cold flat roof (cold deck)
- U-value of an inverted flat roof
- 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, and why two calculators can give different answers for the same wall.