Key Takeaways
| Topic | Key Info (2025) |
|---|---|
| Typical Cost | €7–€16 per m² (fibreglass/mineral wool/rigid board) Up to €29 for spray foam |
| SEAI Grant | €800–€1,500 depending on home type |
| Recommended Depth | 300 mm (two layers of mineral wool) |
| Average Saving | Up to 25 % reduction in heating bills |
| Best Low-Cost Option | Mineral wool rolls |
| Best for Future Conversion | Warm-roof rafter insulation |
| Best Eco Option | Sheep wool or hemp fibre |
Why Attic Insulation Is Important in Ireland
Ireland has a damp, wind-driven climate. Because of this, up to 30 % of a home’s heat can escape through an uninsulated roof. Attic insulation is therefore the most cost-effective upgrade any homeowner can make in a sense; it’s inexpensive, quick to install, and instantly improves heat retention.
Most Irish homes built before 2011 fall below current energy standards, and retrofitting the attic alone can cut heating bills by €300–€500 per year. It’s also a key first step if you plan to improve your BER rating or apply for SEAI grants.
A. Recommended U-Value Targets & Insulation Depth
According to SEAI and Irish Building Regulations (Part L):
| Location | Recommended U-Value | Typical Insulation Depth |
|---|---|---|
| Ceiling / Joist Level (cold attic) | 0.16 W/m²K | ≈ 300 mm mineral wool |
| Rafter Level (warm roof) | 0.20 W/m²K | ≈ 120 mm PIR boards + lining |
- 300 mm mineral wool (laid in two layers cross-hatched of 150mm) hits the ceiling-level target in most lofts.
B. Warm Roof Vs. Cold Roof
| Type | Description | Pros | Cons |
|---|---|---|---|
| Cold Attic | – Insulation laid on ceiling joists. – Roof space above remains cold. | – Cheapest and simplest – Easy to DIY – Ideal if attic is only for storage. | – Must maintain ventilation – Risk of freezing water tanks if not insulated separately. |
| Warm Roof | – Insulation fixed between & below rafters. – The roof structure stays warm. | Perfect for attic conversions or habitable lofts. | – More Expensive – More complex ventilation & vapour control needed. |
Types of Attic Insulation & Average Costs Per Sq Metre in Ireland
| Type | Typical Use | Cost (€/m² installed) | Lifespan | Best For |
|---|---|---|---|---|
| Mineral Wool / Fibreglass Rolls | Between & across joists | €7–€10 | 10–15 yrs | – Most homes – DIY-friendly |
| Blown Cellulose / Loose-fill | Irregular or hard-to-reach lofts | €11–€13 | 15–20 yrs | – Older homes – Retrofit projects |
| Rigid PIR boards | Over joists or between rafters | €12–€16 | 20 + yrs | Attics needing flooring / storage |
| Composite Multifoil + PIR | Under rafters (warm roof) | €15–€20 | 20 + yrs | Future attic conversions |
| Sheep Wool / Hemp | Between joists | €15–€20 | 20 + yrs | – Eco-builds – Vapour-open roofs |
| Spray Foam (open/closed cell) | Directly on rafters | €25–€29 | 25 + yrs | – Complex shapes – Air-tightness focus |
*** Per-m² Guide from BuildTech (Note that prices could range depending on retailer).
1. Mineral Wool / Fibreglass Rolls
Pros – Lowest cost; DIY-friendly; Easy to top-up.
Cons – Needs good ventilation over it; Watch for gaps around downlighters & hatches (airtightness).
Best for – Most homes with unused attic space.
2. Blown Cellulose /Mineral Wool
Pros – Fast install in awkward spaces; Good coverage.
Cons – Can drift if draughty; Needs containment so they don’t drift or settle unevenly over time..
Best for – Irregular joists & hard-to-reach areas.
3. Rigid Boards (PIR)
Pros – Keeps some floor for storage; Good thermal performance for thickness.
Cons – Pricier per m²; Must maintain ventilation path.
Best for – Attics that need a storage deck.
4. Rafter Insulation (Warm Roof) – PIR or Multifoil
Pros – Warms the roof structure; Useful if you plan an attic conversion.
Cons – More complex/costly; Different U-value target (0.20).
Best for – Future habitable attic spaces. SEAI
5. Natural Fibres (Sheep Wool/Hemp)
Pros – Moisture-buffering; Pleasant to handle; Low embodied carbon.
Cons – Higher cost than mineral wool.
6. Spray Foam
Pros – Air-seals awkward rafters/valleys.
Mortgage Caution for Spray Foam – In the UK and sometimes queried by surveyors. Irish lenders said in 2024 that spray foam wasn’t generally a reason to decline a mortgage, but scrutiny exists.
So either avoid the use of spray foam or only use them with reputable installers and breathable build-ups. The Irish Times.
SEAI Attic Insulation Grants
Homeowners can claim funding under SEAI’s Individual Energy Upgrade (Better Energy Homes) scheme if their house was built and occupied before 2011.
| Dwelling Type | Grant Amount (€) |
|---|---|
| Apartment (top floor) | 800 |
| Mid-terrace | 1,200 |
| Semi-detached / End-terrace | 1,300 |
| Detached house | 1,500 |
ELIGIBILITY
- Home must be built and occupied at least before 2011The home must have been built and occupied at least by.
- Work must be done by an SEAI-registered contractor.
- A BER assessment is required after completion.
- Roof insulation can be combined with wall, floor, or heating upgrades for higher grants.
For low-income households, the Fully Funded Energy Upgrade (Warmer Homes Scheme) may cover the entire cost.
Average Cost of Attic Insulation in Ireland
| Home Type | Typical Size (m²) | Approx. Cost Range (€) |
|---|---|---|
| Apartment (top floor) | 35–50 | €600–€900 |
| Mid-terrace | 55–65 | €900–€1,300 |
| Semi-detached | 70–90 | €1,200–€1,800 |
| Detached | 100–120 + | €1,500–€3,000 + |
- Whole-Attic Jobs – Around €1,500–€3,000 depending on size/materials. Dublin often costs €1,000–€1,800 for standard 3-bed top-ups. Premier Insulations
After grants, net costs can fall to:
- €400–€600 for small homes
- €1,000–€1,500 for larger properties
Example for SEAI Grant Impact
| Scenario | Before Grant | SEAI Grant | After Grant | Estimated Annual Heating Saving |
|---|---|---|---|---|
| Semi-D house, 80 m² attic | €1,600 | €1,300 | €300 | €350–€400 |
| Detached home, 120 m² attic | €2,800 | €1,500 | €1,300 | €500–€600 |
You can typically get your money’s worth back in savings in under 3 years – even before grants.
Insulation & Ventilation.
Insulating without proper ventilation can cause condensation and mould. Follow these basics:
- Maintain 50 mm airflow – between insulation and roof felt (cold attic).
- Fit eaves baffles – to stop insulation blocking vents.
- Insulate and draught-proof the attic hatch.
- Cover downlights – with fire-rated caps before insulating.
- Lag water tanks and pipes – above insulation.
Attic Insulation Installation – DIY vs Pro
| Factor | DIY | Professional Installer |
|---|---|---|
| Cost | €400–€900 materials | €1,200–€3,000 full service |
| Time | 1–2 days | ½–1 day |
| Tools needed | Knife, boards, PPE, crawl boards | Specialist blower / cutting tools |
| Quality Assurance | None | Includes BER & SEAI certification |
If claiming a grant, the work must be completed by an SEAI-registered contractor.
What is the Best Time of Year to Insulate my Attic?
- Spring (March–May) – ideal temperatures, moderate humidity.
- Autumn (September–November) – before heating season begins. Avoid mid-winter (cold, wet) and mid-summer (attic heat hazards).
Estimated Annual Energy Savings after Attic Insulation
| Home Type | Before (kWh/yr for heating) | After Attic Upgrade | Energy Saved | Annual Saving (€) |
|---|---|---|---|---|
| Mid-terrace | 11,000 | 8,500 | 2,500 kWh | €300 |
| Semi-detached | 14,000 | 10,000 | 4,000 kWh | €400–€450 |
| Detached | 18,000 | 12,000 | 6,000 kWh | €550–€600 |
Savings are based on oil or gas heating systems. Your savings increase if they’re combined with wall insulation or heat-pump upgrades.
