Wall U-value Comparison in Ireland — Five Systems, the Numbers
On this page
Block 0.15–0.22. ICF 0.13–0.20. Timber frame 0.13–0.18. SIPs 0.10–0.15. CLT 0.13–0.18. W/m²K.
Wall U-value comparison for Irish self-builds (W/m²K, lower is better). Blockwork with external insulation: 0.15–0.22. ICF: 0.13–0.20. Timber frame: 0.13–0.18. SIPs: 0.10–0.15. CLT: 0.13–0.18. Part L 2022 backstop is 0.18 W/m²K. BER A1 typically needs 0.13–0.16. Passive House needs 0.10–0.15. Lower U-value = better insulation. Most systems can hit any target with enough insulation; the trade-off is wall thickness and cost. A 200 mm SIP with 150 mm EPS core achieves 0.10; a 300 mm block wall with 100 mm external insulation achieves 0.15. The wall thickness affects the footprint of the house and the cost of the foundation.
When this matters most
You're at wall-system choice stage and need to compare U-values.
When this doesn't apply
You've already specified the wall system.
Sources
Building Regulations 2023, TGD-L. https://www.gov.ie/
Frequently asked questions
What is the Part L 2022 wall U-value?
0.18 W/m²K is the backstop. BER A1 typically needs 0.13–0.16. Passive House needs 0.10–0.15.
Which wall system has the lowest U-value?
SIPs, at 0.10 W/m²K with a 200 mm panel. Timber frame and ICF reach 0.13–0.18. Blockwork with external insulation reaches 0.15–0.22.
What is U-value?
A measure of how much heat passes through a material. Lower is better. U-value in W/m²K means watts per square metre per degree Kelvin of temperature difference.
When this matters most
You're at wall-system choice stage and need to compare U-values.
When this doesn't apply
You've already specified the wall system.
Where to go next
Next decision
The next step in your build sequence.
- Blockwork for a Self-Build in Ireland — The Default Wall, with External Insulation →
- CLT in Ireland — Cross-Laminated Timber, the Premium Mass-Timber Wall →
- Do Mortgage Lenders Care Which Wall System You Use in Ireland? →
- Timber Frame in Ireland — Why It's the BER A1 Default and What to Watch For →
- Wall System and Insurance in Ireland — What Your Insurer Will and Won't Cover →
- Wall System Build Speed in Ireland — Weeks to Weathertight on a 150 m² House →
Branch into
Adjacent decisions at the same stage.
Watch out for
Common mistakes, hidden costs, gotchas.
- ICF in Ireland — Insulated Concrete Formwork, Cost, Speed, and When to Choose It →
- ICF vs Timber Frame vs Block in Ireland — Cost, Speed, U-value, BER Side by Side →
- SIPs in Ireland — Structural Insulated Panels, Cost, Speed, and When the Premium Is Worth It →
- Wall System Cost per m² in Ireland 2026 — Five Systems, the Live Numbers →
Compare with
Alternative approaches worth knowing.