How to get a detached house built 1940–1969 to an A or B

What A- and B-rated homes like this have

39% of the A- and B-rated ones have a heat pump, and 59% heat with an oil, gas or LPG boiler. Their median heat loss indicator is 2.13, against 3.43 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.

Every certificate for detached houses built 1940–1969, 2019-2026: 4,636 rated A or B, 12,342 rated C to E. What those homes have, not proof of what got them there. SEAI BER Research Tool, file of 26 September 2026 (CC BY 4.0 (SEAI)). A pattern across similar homes, not a fact about yours.

The heat pump line: one job at a time

94% of these homes are above the line. The share of those that each job, done on its own, brings under it:

The 5,823 certificates for a sale or letting for detached houses built 1940–1969 above the line. SEAI BER Research Tool, file of 26 September 2026 (CC BY 4.0 (SEAI)). A pattern across similar homes, not a fact about yours.

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

97% of these homes are short of B2. The share of those that each job, done on its own, gets there:

The 8,955 certificates for a sale or letting for detached houses built 1940–1969 short of B2. SEAI BER Research Tool, file of 26 September 2026 (CC BY 4.0 (SEAI)). A pattern across similar homes, not a fact about yours.

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.

Self-managed: about €30,150 in grants against works of about €79,273, leaving about €49,123 to pay.

Attic insulation: Attic insulation grant, read 13 Jul 2026 · External wall insulation (the wrap): Wall insulation grant, read 8 Jun 2026 · Windows: Windows and doors grant, read 13 Jul 2026 · External doors: Windows and doors grant, read 13 Jul 2026 · Costs are SEAI’s medians, not quotes. Whether a grant is paid is SEAI’s decision on your application.

The full worked plan, step by step

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