Insulation, Airtightness and Cladding — Fabric First Is Cheaper Than Heat After
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When this matters most
You're at detailed design and specifying fabric choices. Or you're existing stock and considering a deep retrofit.
When this doesn't apply
You're replacing windows on a finished house (Stage 9) or you're at sign-off with fabric already specified.
Frequently asked questions
What U-value do I need for Part L 2022?
Wall 0.18, roof 0.16, floor 0.13. A1 BER on a new self-build usually needs wall 0.13–0.16, roof 0.13, floor 0.13.
What is airtightness?
How much air leaks uncontrolled through the building envelope. Measured in air-changes per hour (ach) at 50 Pa pressure (m³/m²·hr). Passive House requires ≤0.6. BER A1 typically requires 1.0–2.0.
Can I do an airtightness test mid-build?
Yes — an interim test at first-fix (before plastering) catches the cheap fixes. Full test at completion.
What's the cheapest cladding?
Cement render on blockwork, €80–€140/m² installed. Brick is €140–€220/m². Timber (cladding boards) is €110–€180/m². Zinc standing-seam is €180–€300/m².
Does the architect or engineer pick the cladding?
The architect picks, often with planning constraints. In rural areas, slate, brick, and timber are more likely to get planning consent than render.
Sources
Building Regulations 2023, TGD Part L (Conservation of fuel and energy — Dwellings), Department of Housing. https://www.gov.ie/
SEAI, Deep Retrofit Cost Benchmarks 2024. https://www.seai.ie/
Frequently asked questions
What U-value do I need for Part L 2022?
Wall 0.18, roof 0.16, floor 0.13. A1 BER on a new self-build usually needs wall 0.13–0.16, roof 0.13, floor 0.13.
What is airtightness?
How much air leaks uncontrolled through the building envelope. Measured in air-changes per hour (ach) at 50 Pa pressure (m³/m²·hr). Passive House requires ≤0.6. BER A1 typically requires 1.0–2.0.
Can I do an airtightness test mid-build?
Yes — an interim test at first-fix (before plastering) catches the cheap fixes. Full test at completion.
What's the cheapest cladding?
Cement render on blockwork, €80–€140/m² installed. Brick is €140–€220/m². Timber (cladding boards) is €110–€180/m². Zinc standing-seam is €180–€300/m².
Does the architect or engineer pick the cladding?
The architect picks, often with planning constraints. In rural areas, slate, brick, and timber are more likely to get planning consent than render.
Related guides
- Airtightness in Ireland — Part L 1–3 m³/m²·hr, Passive House ≤0.6, and the Blower Door Test
- Brick Cladding in Ireland — Cost, Lifespan, and When to Choose It
- Cladding in Ireland — Render, Brick, Timber, and Zinc, Compared by Cost and Planning
- External Insulation in Ireland — The EWI Decision for Blockwork, BER, and Thermal Bridging
- Internal Wall Insulation in Ireland — When to Use It and Why Most Self-Builders Don't
- Lintels and Reveals in Ireland — The Detailing That Makes or Breaks Airtightness
- Render in Ireland — Cement, Lime, Silicone, and Acrylic, Compared
- Stone Cladding in Ireland — Real Stone vs Stone Veneer, Cost, and Heritage Use
- Timber Cladding in Ireland — Cost, Maintenance, and Best Species for Irish Weather
- Wall Insulation in Ireland — PIR, EPS, Mineral Wool, and What Hits the U-value Target
- Zinc Cladding in Ireland — Standing-Seam, Cost, and Lifespan