Insulation, Airtightness and Cladding — Fabric First Is Cheaper Than Heat After
On this page
Spending €10,000 more on fabric saves €20,000 in heat-pump sizing and €600/year in running cost.
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.
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.
Briefs in this stage
11 in-depth answers for this stage of the build. Pick the one that matches your question.
Airtightness in Ireland — Part L 1–3 m³/m²·hr, Passive House ≤0.6, and the Blower Door Test
Part L 2022: 1–3 m³/m²·hr at 50 Pa. BER A1: typically 1–2. Passive House: ≤0.6. Tested with a blower door at completion.
airtightness Ireland self buildRead brief →
Brick Cladding in Ireland — Cost, Lifespan, and When to Choose It
Brick: €140–€220/m². 80–100+ year lifespan. Most durable cladding. Best for rural and heritage sites.
brick cladding IrelandRead brief →
Cladding in Ireland — Render, Brick, Timber, and Zinc, Compared by Cost and Planning
Render €80–€140/m². Brick €140–€220/m². Timber €110–€180/m². Zinc €180–€300/m². Planning matters in rural areas.
cladding Ireland optionsRead brief →
External Insulation in Ireland — The EWI Decision for Blockwork, BER, and Thermal Bridging
External insulation (EWI): 50–150 mm on the outside of the wall. Eliminates thermal bridges. Adds 5–15% to wall cost.
external insulation IrelandRead brief →
Internal Wall Insulation in Ireland — When to Use It and Why Most Self-Builders Don't
Internal insulation: 50–100 mm on the inside of the wall. Used in retrofit; rarely in new build. Loses floor area and creates thermal bridges.
internal wall insulation IrelandRead brief →
Lintels and Reveals in Ireland — The Detailing That Makes or Breaks Airtightness
Lintels: structural beam over an opening. Reveals: the wall detail around windows. Critical for airtightness and thermal bridging.
lintels and reveals IrelandRead brief →
Render in Ireland — Cement, Lime, Silicone, and Acrylic, Compared
Cement render €80–€140/m². Lime render €100–€160/m². Silicone render €110–€170/m². Acrylic render €90–€140/m².
render Ireland optionsRead brief →
Stone Cladding in Ireland — Real Stone vs Stone Veneer, Cost, and Heritage Use
Real stone: €200–€350/m². Stone veneer: €80–€150/m². Heavy. Heritage sites often require real stone.
stone cladding IrelandRead brief →
Timber Cladding in Ireland — Cost, Maintenance, and Best Species for Irish Weather
Timber cladding: €110–€180/m². Repaint every 8–12 years. Cedar, larch, and oak are the best species for Irish weather.
timber cladding IrelandRead brief →
Wall Insulation in Ireland — PIR, EPS, Mineral Wool, and What Hits the U-value Target
PIR 0.022 W/m²K. Mineral wool 0.035. EPS 0.038. 150 mm PIR + 50 mm insulated sheathing hits 0.13 W/m²K.
wall insulation IrelandRead brief →
Zinc Cladding in Ireland — Standing-Seam, Cost, and Lifespan
Zinc standing-seam: €180–€300/m². 60–100 year lifespan. Premium option. Architectural finish.
zinc cladding IrelandRead brief →
Where to go next
Next decision
The next step in your build sequence.
- Airtightness in Ireland — Part L 1–3 m³/m²·hr, Passive House ≤0.6, and the Blower Door Test →
- External Insulation in Ireland — The EWI Decision for Blockwork, BER, and Thermal Bridging →
- Lintels and Reveals in Ireland — The Detailing That Makes or Breaks Airtightness →
- Wall Insulation in Ireland — PIR, EPS, Mineral Wool, and What Hits the U-value Target →
Branch into
Adjacent decisions at the same stage.
Watch out for
Common mistakes, hidden costs, gotchas.
- Brick Cladding in Ireland — Cost, Lifespan, and When to Choose It →
- Cladding in Ireland — Render, Brick, Timber, and Zinc, Compared by Cost and Planning →
- 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 →
- Zinc Cladding in Ireland — Standing-Seam, Cost, and Lifespan →