What do A- and B-rated homes have that others do not?

In published BERs for houses built before 2011, 47% of the A- and B-rated ones have solar panels, 63% insulated walls and 21% a heat pump, against 10%, 25% and 0% of those rated C to E. How high a home can go depends on the house.

What one job most often gets a home under the heat pump line?

For homes just above it, replacing the windows: on its own it brings 84% of them under the line, in published BERs for a sale or letting.

How to improve a BER: what A and B homes have

In published BERs, 63% of A- and B-rated houses have insulated walls, 47% solar panels and 21% a heat pump. How high a home can go depends on the house.

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A housing estate street in Letterkenny: dry-dash semi-detached houses on both sides, cars at the kerb, a grass island with a young tree, hills at the end of the road. — Landscaped road island in the Old Town housing estate, Letterkenny · Humphrey Bolton · CC BY-SA 2.0 · Photo credits

The numbers

B2 or better now: 8%
Under the heat pump line: 47%
Just above the line: replacing the windows gets them under: 84%
One grade short of B2: a heat pump gets them there: 99%

Certificates for a sale or letting, January 2019 to September 2026: 265,008, 161,076 of them with a heat loss figure (from July 2022). "Just above the line" is the 15,988 with a heat loss indicator between 2.3 and 2.5; "one grade short" is the 30,735 rated B3. SEAI BER Research Tool, file of 26 September 2026 (CC BY 4.0 (SEAI)). A pattern across similar homes, not a fact about yours.

By house type and age

How to get a detached house to an A or B
A or B now, by age: 4% built before 1940, 6% built 1940–1969, 8% built 1970–1989, 19% built 1990–2004, 55% built 2005–2010.
How to get a semi-detached house to an A or B
A or B now, by age: 7% built before 1940, 7% built 1940–1969, 7% built 1970–1989, 11% built 1990–2004, 41% built 2005–2010.
How to get a mid-terrace house to an A or B
A or B now, by age: 7% built before 1940, 6% built 1940–1969, 9% built 1970–1989, 21% built 1990–2004, 64% built 2005–2010.
How to get an apartment to an A or B
A or B now, by age: 10% built before 1940, 9% built 1940–1969, 7% built 1970–1989, 17% built 1990–2004, 46% built 2005–2010.

The detail

What A- and B-rated houses have

Share of A or B and of C to E certificates with each upgrade, houses built before 2011
	A or B	C to E
Solar panels	47%	10%
Insulated walls	63%	25%
A heat pump	21%	0%
An insulated floor	74%	40%
New high-performance windows	26%	4%
An attic insulated to the grant standard	33%	19%
Mechanical ventilation	7%	1%

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 a house built before 2011, 2019-2026. 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

Of the 86,127 homes above it, one job on its own brings 33% under. Of the 15,988 just above it, one job is enough for 93%:

Single jobs that bring a home under the heat pump line
One job on its own	All above the line	Just above it
Replacing the windows	20%	84%
Insulating the walls	13%	17%
Topping up the attic	10%	47%
Blocking unused chimneys and flues	4%	19%
Draught-proofing	1%	3%

Certificates for a sale or letting with a heat loss figure. 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.