How to get a detached house built before 1940 to an A or B
An insulated floor and a heat pump are what most set the A- and B-rated detached houses built before 1940 apart in published BERs. How high a home can go depends on the house.
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The numbers
- A or B now
- 4%
- Under the heat pump line
- 4%
- Grants in the plan
- €22,150
- You pay
- €30,623
The one job that most often gets these homes under the heat pump line is insulating the walls: on its own it does it for 5% of the ones above it. To reach B2, a heat pump on its own gets 10% of those short of it there.
The detail
What A- and B-rated homes like this have
| A or B | C to E | |
|---|---|---|
| Solar panels | 47% | 23% |
| Insulated walls | 60% | 10% |
| A heat pump | 47% | 1% |
| An insulated floor | 67% | 8% |
| New high-performance windows | 53% | 6% |
| An attic insulated to the grant standard | 39% | 10% |
| Mechanical ventilation | 26% | 2% |
47% of the A- and B-rated ones have a heat pump, and 50% heat with an oil, gas or LPG boiler. Their median heat loss indicator is 2.05, against 3.69 for the C-to-E ones.
Solar PV · Walls U ≤ 0.37 · Heat pump · Floor U ≤ 0.45 · Windows U ≤ 1.6 · Roof U ≤ 0.16 · Mechanical ventilation. A or B = A1 to B3; C to E = C1 to E2, on the old scale.
The heat pump line: one job at a time
96% of these homes are above the line. The share of those that each job, done on its own, brings under it:
| One job on its own | Brought under the line |
|---|---|
| Insulating the walls | 5% |
| Topping up the attic | 1% |
| Replacing the windows | 1% |
| Blocking unused chimneys and flues | 0% |
| Draught-proofing | 0% |
| Any one of them | 6% |
Each job is applied on its own to each certificate with a simplified heat balance, not DEAP. The model’s HLI matches SEAI’s published HLI to a median ratio of 0.997 (IQR 0.985–1.01). Method: research/ber, thresholds.
The B2 line: one job at a time
98% of these homes are short of B2. The share of those that each job, done on its own, gets there:
| One job on its own | Reach B2 |
|---|---|
| A heat pump | 10% |
| Solar panels | 3% |
| Insulating the walls | 0% |
| Topping up the attic | 0% |
| Replacing the windows | 0% |
| Any one of them | 11% |
The worked plan, in order
The engine’s plan for the house published BERs most often describe for this age, in the order SEAI’s rules need. A plan, not a BER assessment.
- 1Energy assessment (BER and advisory report)no grant · €280
- 2Attic insulation€2,000 grant · €2,700
- 2Windows€4,000 grant · €10,453
- 2External doors€1,600 grant · €4,300
- 2Airtightnessno grant · €1,600
- 2Mechanical ventilationno grant · €4,000
- 3Heat pump technical assessment€200 grant · €500
- 3Heat pump (air to water)€6,500 grant · €17,000
- 3Radiators and pipework for the heat pump€2,000 grant
- 3Renewable heat bonus€4,000 grant
- 4Solar panels (PV)€1,800 grant · €11,100
Self-managed: about €22,150 in grants against works of about €52,773, leaving about €30,623 to pay.
The two lines that matter
The heat pump line: a BER that shows the house holds heat well enough (a heat loss indicator of 2.3 or less) means no technical assessment before the heat pump grant.
“You do not need one if your valid BER says your Heat Loss Indicator is equal to or less than 2.3 W/(K.m2).” SEAI: Heat pump systems grant, read 25 Sept 2026
The windows grant asks for the same line after the works.
“The property must meet a Heat Loss Indicator (HLI) value of 2.3” SEAI: Windows and doors grant, read 13 Jul 2026
The B2 line: SEAI’s One Stop Shop scheme asks for a B2 after the works, plus a heat pump or a big cut in the energy the house uses.
“Your home must achieve a minimum post works BER of B2, plus either have installed a heat pump or achieved a primary energy uplift of 100 kWh/m²/yr.” SEAI: One Stop Shop: multiple energy upgrades (grant table), read 30 Apr 2026
B2 is the lower half of the old B band.
“B2 ≤ 125” Source: CSO Domestic BERs Q2 2026 — background notes, read 27 Sept 2026
Certificates since 24 May 2026 use a new scale with a single B, which covers a little more than the old B2. The figures here are from certificates on the old scale.
“On 24 May 2026 the Building Energy Rating (BER) scale was modified in line with new EU wide regulations under the Energy Performance of Buildings Directive (EPBD). The scale has been simplified from fifteen points to eight (A0, A, B, C, D, E, F, G).” Source: CSO Domestic BERs Q2 2026 — background notes, read 27 Sept 2026