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Dwellings — TGD L 2022, Conservation of Fuel and Energy
Table 1 sets maximum area-weighted elemental U-values for a new dwelling and for an extension, with a second column for the worst any individual section of an element may be. Table 5 sets the figures for material alterations and material changes of use, and it is Table 5 that distinguishes cavity walls suitable for cavity fill from other walls, and a pitched roof insulated at the ceiling from one insulated on the slope. Compliance for a new dwelling is then shown in DEAP: an MPEPC of 0.30 and an MPCPC of 0.35 against the reference dwelling of Appendix C, which is why a fabric-first NZEB design usually sits well below Table 1.
| Element | Table 1 — new dwellings and extensions | Individual section | Table 5 — material alterations |
|---|---|---|---|
| Pitched roof, insulation at ceiling | 0.16 | 0.3 | 0.16 |
| Pitched roof, insulation on slope | 0.16 | 0.3 | 0.25 |
| Flat roof | 0.20 | 0.3 | 0.25 |
| Walls | 0.18 | 0.6 | cavity 0.55 / other 0.35 |
| Ground floors | 0.18 (0.15 with underfloor heating) | 0.6 | 0.45 where replaced |
| Other exposed floors | 0.18 | 0.6 | 0.25 |
| External doors, windows, rooflights | 1.4 | 3.0 | 1.4 |
All values W/m²K. Sources: Technical Guidance Document L 2022 — Conservation of Fuel and Energy — Dwellings (Government of Ireland, applies to works from 25 October 2022), paragraph 1.3.2.2 Table 1 (p.22), paragraph 2.1.2.5 Table 5 (p.36), Appendix C Table C1 (p.73). A draft TGD L 2025 issued for consultation in December 2024 keeps Table 1 unchanged and adds a 0.31 row to Table 5 for 100 mm cavity walls; it is not in force.
Buildings other than dwellings — TGD L 2022
| Element | Table 1 — new buildings and extensions | Table 10 — material alterations | Table 11 — retained elements: threshold → target |
|---|---|---|---|
| Pitched roof, insulation at ceiling | 0.16 | 0.16 | 0.16 → 0.16 |
| Pitched roof, insulation on slope | 0.16 | 0.25 | 0.35 → 0.25 |
| Flat roof | 0.20 | 0.25 | 0.35 → 0.25 |
| Walls | 0.21 | cavity 0.55 / other 0.35 | 0.55 → 0.55 cavity / 0.35 other |
| Ground floors | 0.21 | 0.45 where replaced | 0.45 → 0.45 |
| Other exposed floors | 0.21 | 0.25 | 0.6 → 0.25 |
| Personnel doors, windows, rooflights | 1.6 | 1.6 | 3.6 → 1.6 |
| Curtain walling | 1.8 | 1.8 | 3.6 → 1.8 |
| Vehicle access doors / high-usage entrance doors | 1.5 / 3.0 | — | — |
Sources: Technical Guidance Document L 2022 — Buildings other than Dwellings, paragraph 1.3.2.2 Table 1 (p.28), paragraph 2.1.2.4 Table 10 (p.57), paragraphs 2.1.2.5–2.1.2.7 Table 11 (p.58). Compliance for a new building is MPEPC ≤ 1.0 and MPCPC ≤ 1.15 in NEAP against the Appendix C reference building (roof 0.15, wall 0.18, floor 0.15, windows 1.4 side-lit / 1.6 top-lit, Table C1 p.103).
The same wall, judged four ways
A partial-fill cavity wall — 102.5 mm brick, 50 mm residual cavity, 100 mm PIR (λ 0.022), 100 mm dense block and plasterboard — calculates to 0.20 W/m²K with the standard air-gap correction. In England it passes the 0.26 dwelling backstop. In Wales and Ireland it fails the 0.18 maximum; in Scotland it fails 0.17. Swap the PIR for 150 mm of full-fill mineral wool (λ 0.032) on aircrete and it lands at 0.18 — a pass in Ireland and Wales, still short in Scotland. For an Irish non-domestic building the 0.21 maximum makes the original wall a pass.
How U-Monkey applies it
Pick Ireland and Dwelling or Non-domestic under the verdict. New build and extensions are judged against Table 1; a material alteration against Table 5 (or Table 10), with the cavity / other wall choice made above the result; an existing element as built against the Table 5 figure that triggers major-renovation works, or the Table 11 threshold for a non-domestic change of use. Windows and doors entered as specified elements use the same tables. The free PDF names the document and table in the verdict banner and the footer.
Frequently asked questions
What U-values does Part L require for a new house in Ireland?
Table 1 of Technical Guidance Document L 2022 (Dwellings) sets the maximum area-weighted elemental U-values: walls 0.18, ground floors and other exposed floors 0.18, pitched roofs 0.16 whether the insulation is at ceiling level or on the slope, flat roofs 0.20, and external doors, windows and rooflights 1.4 W/m²K. No individual section of a roof may be worse than 0.3, or of a wall or floor 0.6. A floor with underfloor heating should be 0.15. Compliance itself is the DEAP calculation — an MPEPC of 0.30 and MPCPC of 0.35 against the reference dwelling — so most NZEB designs go well beyond Table 1.
Which U-values apply to an extension or a material alteration?
Extensions use the same Table 1 figures as a new dwelling (paragraph 2.1.2.1). Material alterations and material changes of use use Table 5: pitched roof insulated at ceiling 0.16, insulated on the slope 0.25, flat roof 0.25, cavity walls suitable for cavity fill 0.55, other walls 0.35, ground floors 0.45 (only where the floor is being replaced), other exposed floors 0.25, and windows, doors, rooflights and curtain walling 1.4 W/m²K. Where more than 25 % of the envelope is renovated, the major-renovation rules in section 2.3 add cost-optimal measures or a 125 kWh/m²/yr primary-energy target.
How do the Irish figures compare with England, Wales and Scotland?
Walls: Ireland 0.18, England 0.26 backstop (0.18 notional), Wales 0.18, Scotland 0.17. Floors: Ireland 0.18, England 0.18, Wales 0.15, Scotland 0.15. Pitched roofs: Ireland 0.16, England 0.16, Wales 0.13, Scotland 0.12. Windows: Ireland 1.4, England 1.6 backstop (1.2 notional), Wales 1.4, Scotland 1.4. Ireland’s Table 1 is closer to a real design target than England’s backstop, but its regulated metric is primary energy and carbon in DEAP rather than the fabric alone.
What about buildings other than dwellings in Ireland?
TGD L 2022 (Buildings other than Dwellings) Table 1: walls 0.21, ground and other exposed floors 0.21, pitched roofs 0.16, flat roofs 0.20, external personnel doors, windows and rooflights 1.6, curtain walling 1.8, vehicle access doors 1.5 and high-usage entrance doors 3.0 W/m²K. Table 10 covers material alterations and Table 11 retained elements on a change of use, which is the only Irish table with a threshold column. Compliance is MPEPC 1.0 / MPCPC 1.15 in NEAP against a reference building with roof 0.15, wall 0.18 and floor 0.15.
Does U-Monkey use the Irish tables?
Yes. Under the verdict choose Ireland and either Dwelling or Non-domestic; the pass/fail, the hint text and the PDF footer switch to TGD L and name the table used. The U-value itself is the same BS EN ISO 6946 calculation, and the product library includes the Irish-market boards (Kingspan, Unilin, Mannok, Kore, Xtratherm) with their declared conductivities.
Elsewhere: Scotland (Section 6) · Wales (Part L 2022) · non-domestic buildings · England dwellings. Full tutorial: how to use U-Monkey.