Upgrade · Fabric · the roof · BER file 26 Sep 2026 · checked 8 Sep 2026
9 in 10 homes sold or let have an attic short of the grant standard
Attic insulation is a thick layer laid over the ceilings of the top rooms. 89.7% of homes sold or let have one short of the grant's standard (SEAI BER file, 26 Sep 2026). It's the cheapest job on the list: SEAI's typical price for a semi-detached house is €2,101 and the grant pays €1,500. On its own it moves a rating only 6.1 points, but it cuts the heat everything else has to replace.
Mineral wool pressed in between the roof timbers. The cheapest job on the list, and usually the first.
Unrecognizable worker insulating with stone wool · Erik Mclean · Pexels License
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9 in 10
Homes sold or let have an attic short of the grant standard
10.3% at U ≤ 0.16 · BER file 26 Sep 2026
BER assessment6.1
Points on the BER scale it adds, for the typical home it applies to
kWh/m²/yr · research lane, BER file 26 Sep 2026
Our model33%
Older A- and B-rated houses with attic at the grant standard. Rated C to E: 19%
Roof U ≤ 0.16 · built before 2011 · BER file 26 Sep 2026
BER assessment71%
Of SEAI's typical semi-D price paid by the grant
€1,500 of €2,101 · SEAI H1 2026
Published figureUpdated · grants checked · BER file · prices SEAI H1 2026 · How we know · Corrections
Where this sits · the heat chain
Most heat leaves through the walls, roof, floor and windows. Fix these first and the heating has less to replace.
- Fabricwalls, roof, floor, windows
- Airdraughts and ventilation
- Heatheat pump or boiler, radiators, controls
- Usebills, comfort, the BER
- The idea behind itFollow the heat
- You are hereAttic insulation
- Next questionHow much does SEAI pay towards attic insulation?
10% of the heat a semi-detached house built 1971–80 loses goes through its roof
Where a typical semi-detached house built 1971–80 loses its heat. This job acts on the roof, pin 1. BER assessment
10% of the heat a semi-detached house built 1971–80 loses goes through its roof
Walls 32%, windows 18%, air 17%, floor 11%, roof 10%, junctions 10%, doors 2%.
A section through a semi-detached house built 1971–80, front to back. Each arrow's width is that element's share of the heat the house loses for every degree it is warmer inside than out, from the insulation values and areas on 4,498 BER certificates for homes sold or let, assessed 2022–26. The median wall lets through 1.10 watts per square metre per degree, the roof 0.40 and the windows 2.80; the median heat loss indicator is 3.15, over the heat pump line of 2.3. Air (draughts, vents and open chimneys) isn't measured on a BER: it is what's left once the six measured elements are subtracted, so it carries the most uncertainty. The numbered pins show where each of the jobs acts, in the order they're usually done.
EstimateAir is estimated as the remainder (heat loss indicator × floor area, less walls, roof, floor, windows, doors and thermal bridging). Shares are rounded to sum to 100.
Sources: SEAI BER Research Tool, 8 Sep 2026 · Certificates for a sale or private letting assessed 2022–26 with a heat loss indicator: semi-detached house built 1971–80, 4,498 certificates
The numbers
| Element | Share of heat loss | Median |
|---|---|---|
| Walls | 32.0% | 1.10 W per m² per degree, 89 m² |
| Windows | 17.6% | 2.80 W per m² per degree, 21 m² |
| Air (estimated) | 16.8% | the remainder |
| Floor | 10.7% | 0.64 W per m² per degree, 60 m² |
| Roof | 10.5% | 0.40 W per m² per degree, 61 m² |
| Junctions | 10.2% | cold bridges at joins |
| Doors | 2.2% | 2.95 W per m² per degree, 2 m² |
On its own, attic insulation moves a rating 6.1 points; a heat pump, 93
What one job on its own does to the typical home's rating, where the job applies. One letter on the new scale is 50 points. Our model
Attic insulation: 6.1 points on its own, where it applies
Where the job applies, the median gain is 93 kilowatt-hours per square metre a year for a heat pump, 60.7 for solar panels, 46.7 for wall insulation and 10.4 for new windows. One letter on the new scale is 50.
Each bar is the median improvement to a home's BER from that one job on its own, among homes sold or let where the job applies, worked out on each certificate's own figures. A heat pump moves the rating nearly two letters in the D to F range; attic insulation, draught-stripping and blocking chimneys barely move the rating on their own. The bracket shows one letter's width (50, for D, E and F). The bars are not additive.
EstimateOur model: the research lane's one-job recalculation on each certificate's own figures (BER file of 26 Sep 2026, not the site's 8 Sep file). It matches SEAI’s published heat loss to a median ratio of 1.00 and uses the electricity factor in force on each certificate’s date.
Sources: fixmyber research lane, research/ber/s4_thresholds.py, 26 Sep 2026
The numbers
| Job | Median gain, kWh per m² a year |
|---|---|
| Heat pump | 93 |
| Solar panels | 60.7 |
| Wall insulation | 46.7 |
| New windows | 10.4 |
| Attic insulation | 6.1 |
| Blocking chimneys | 2.4 |
| Draught-stripping | 0.4 |
Older A- and B-rated houses are 2 times as likely to have attic at the grant standard
What older houses rated A or B have, against those rated C to E. BER assessment
33% of older A- and B-rated houses have attic at the grant standard; 19% of those rated C to E
The biggest gap is insulated walls: 63% against 25%.
- Insulated walls. Rated A or B: 63%. Rated C to E: 25%.
- Solar panels. Rated A or B: 47%. Rated C to E: 10%.
- An insulated floor. Rated A or B: 74%. Rated C to E: 40%.
- Attic at the grant standard. Rated A or B: 33%. Rated C to E: 19%.
- High-performance windows. Rated A or B: 26%. Rated C to E: 3.8%.
- A heat pump. Rated A or B: 21%. Rated C to E: 0.2%.
- Solar water heating. Rated A or B: 7.8%. Rated C to E: 2.2%.
- Mechanical ventilation. Rated A or B: 7.2%. Rated C to E: 0.9%.
Each pair of bars is the share of houses built before 2011 that have the upgrade, among those rated A or B (dark) and those rated C to E (grey), from every certificate issued 2019-2026. Attic at the grant standard: 33.3% against 19.3%. It shows what the better-rated houses have, not proof of what got them there: newer houses are more often A or B and were built with some of these.
Sources: SEAI BER Research Tool, every existing-home certificate 2019–26 for houses built before 2011 (440,689 certificates), 26 Sep 2026 · Insulated walls: Walls U ≤ 0.37 · Solar panels: Solar PV · An insulated floor: Floor U ≤ 0.45 · Attic at the grant standard: Roof U ≤ 0.16 · High-performance windows: Windows U ≤ 1.6 · A heat pump: Heat pump · Solar water heating: Solar water · Mechanical ventilation: Mechanical ventilation
The numbers
| Upgrade | Rated A or B | Rated C to E |
|---|---|---|
| Insulated walls | 62.8% | 25.4% |
| Solar panels | 46.9% | 9.7% |
| An insulated floor | 73.6% | 39.9% |
| Attic at the grant standard | 33.3% | 19.3% |
| High-performance windows | 26.1% | 3.8% |
| A heat pump | 20.9% | 0.2% |
| Solar water heating | 7.8% | 2.2% |
| Mechanical ventilation | 7.2% | 0.9% |
What attic insulation is, and why it goes first
Attic insulation is a thick layer laid over the ceilings of the top rooms. Heat you paid for stays in the rooms instead of rising into a cold roof.
What the job is
Two rolls of mineral wool, laid at right angles to each other over the attic floor, to a depth of about 300 mm. That's the whole job in most houses. The contractor lays it over the joists rather than between them, boards a walkway to the water tank and the hatch, lags the tank and the pipes, and makes sure air can still move through the roof space.
It takes half a day. Nobody moves out, nothing gets knocked, and the only thing you lose is headroom in the attic for storage.
If the attic is a bedroom or a playroom, the layer goes against the slope of the roof instead, in rigid boards. That's a different job with a different grant, and it costs more.
Compared with a cold roof
| Before | After | |
|---|---|---|
| What's up there | patchy wool between the joists, often 100 mm | about 300 mm, laid across the joists |
| Where the heat goes | up through the ceiling and out the roof | stays in the rooms below |
| The attic itself | mild, because your heat is warming it | properly cold, and ventilated for it |
| Storage | anything, anywhere | a boarded walkway; boxes need raised boards |
| Time and mess | — | half a day, no rooms cleared |
SEAI's figure for a badly insulated roof and walls together is up to 30% of a home's heat. That's the reason this job goes first: it is the cheapest thing on the list and it takes the biggest single bite out of the loss.
Grant €1,100 to €2,000 by house type, €1,500 for a semi-detached or end of terrace; rafter-level work €1,500 to €3,000. SEAI median cost €2,101 (semi). Grant paid once per MPRN. Amounts verified 2026-10-03.
Where the saving comes from
Warm air rises, and a ceiling is thin. Insulation doesn't stop heat, it slows it down: the wool traps air in tiny pockets, and still air is a poor conductor, so the heat takes far longer to get through. Slow the loss and the boiler or the heat pump runs for fewer hours to hold the same room temperature. Nothing about the heating system changes — it just has less work to do.
This is also the job that makes every later job cheaper. A house that holds its heat needs a smaller heat pump, and it is the attic and the walls that usually get an older house through SEAI's heat-loss test.
Modelled roof heat loss for that group of homes: U 0.26 → 0.20 W/m²K after the works. SEAI's standard for a grant-aided attic job is 0.16 W/m²K, roughly 300 mm. detached|1970-1989|D|oil: cost p50 €36,848, grant €22,300, you pay p25–p75 €7,300–€21,700, saving €1,797/yr, payback 4.7–12.4 yrs, n=23,707, confidence 0.9
Questions people ask
- How much insulation is enough?
- SEAI put the ideal at 300 mm at ceiling level. Older houses often have 100 mm that has settled, gone patchy, or was never laid over the joists at the eaves. Topping up to 300 mm counts as a job worth doing, and it is what the grant is for.
- Can I still use the attic for storage?
- Yes, but not the way you used it before. The insulation is deeper than the joists, so anything resting on the joists is now squashing it. A proper job includes a boarded walkway to the tank and the hatch. If you store a lot up there, ask the contractor to raise the boards above the insulation.
- Will the attic get damp?
- It can, if the job is done badly. A cold attic needs air moving through it, because the moisture that used to drift up and out now has to leave some other way. SEAI are explicit that ventilation goes in as part of the work. The tank and its pipes get lagged at the same time, because the attic is now colder than it used to be.
How we know
- Ratings: From SEAI's BER Research Tool (files of 8 Sep 2026 and 26 Sep 2026): certificates for homes sold or let, and every certificate for houses built before 2011. A BER is a standard calculation, not a meter reading.
- One job at a time: Our model reworks each certificate with one job done, on the BER file of 26 Sep 2026. Its heat loss matches SEAI's own figure to a median ratio of 1.00. A group figure, not an assessment of your house.
- Grants and prices: SEAI's grant pages, read on the dates shown, and SEAI's median costs of individual upgrades for 2025. A median is a middle price, not a quote.
Sources
seai.ie · insulation · seai.ie · attic insulation · seai.ie · Median costs of individual energy upgrades
Found a mistake? Every fix is dated on Corrections. Method in full: How we know.
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Updated · grants checked · BER file · prices SEAI H1 2026 · How we know · Corrections