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Upgrades · ten jobs · BER file 8 Sep 2026 · SEAI median costs H1 2026

A heat pump moves a BER nine times as far as new windows

In the typical home where each job applies, a heat pump moves the rating 93 points on the scale (our model, BER file of 26 Sep 2026). Solar panels come next, then wall insulation. New windows move it 10 points, and attic insulation 6. They still matter: they cut the heat a heat pump has to replace.

A terrace of single-storey homes under scaffolding and pink debris netting, the roof stripped back.

Bungalows in Hull, England, being wrapped in outside insulation. The walls get thicker; the rooms stay as they are.

Garrick Close, Kingston upon Hull: bungalow renovations, September 2023 · Hullian111 · CC BY-SA 4.0

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93

Points on the BER scale a heat pump adds, for the typical home

kWh/m²/yr · research lane, BER file 26 Sep 2026

Our model

9 in 10

Homes sold or let with an attic short of the grant standard

10.3% at U ≤ 0.16 · BER file 26 Sep 2026

BER assessment

89.6%

Homes sold or let with older windows

U > 2.0 · BER file 26 Sep 2026

BER assessment

46.6%

Homes sold or let already under the heat pump line

HLI ≤ 2.3 · BER file 8 Sep 2026 · n=161,297

BER assessment

Updated · grants checked · BER file · prices SEAI H1 2026 · How we know · Corrections

Where this sits · the heat chain

This page covers all four links. Fix the fabric first, then the air, then the heat. Every job below sits on one of them.

  1. Fabricwalls, roof, floor, windows
  2. Airdraughts and ventilation
  3. Heatheat pump or boiler, radiators, controls
  4. Usebills, comfort, the BER
  1. The idea behind itFollow the heat
  2. You are hereUpgrades
  3. Next questionHow do you get a house like yours to a B?

The walls lose more heat than the roof and floor together

Where a typical semi-detached house built 1971–80 loses its heat, with the ten jobs pinned where they act. BER assessment

Figure 1BER assessment

A third of the heat a semi-detached house built 1971–80 loses goes through its walls

Walls 32%, windows 18%, air 17%, floor 11%, roof 10%, junctions 10%, doors 2%.

Where a semi-detached house built 1971–80 loses its heat: walls 32%Section through a semi-detached house built 1971–80, front to back. Share of the heat lost per degree of temperature difference, by element: walls 32%, windows 18%, air 17%, floor 11%, roof 10%, junctions 10%, doors 2%. Air (draughts, vents and chimneys) is estimated as the remainder. Arrow widths are to scale. Medians of 4,498 homes sold or let, assessed 2022–26. Numbered pins mark where each job acts: 1 attic, 2 cavity wall, 3 internal wall, 4 external wall, 5 windows and doors, 6 heating controls, 7 heat pump, 8 solar water, 9 solar panels, 10 boiler.SECTION, FRONT TO BACK · SEMI-DETACHED HOUSE BUILT 1971–80arrow widths to scale · dashed = estimated32%WallsU 1.10 · 89 m²18%WindowsU 2.80 · 21 m²2%DoorsU 2.95 · 2 m²17%Airdraughts, vents, chimney (est.)10%RoofU 0.40 · 61 m²11%FloorU 0.64 · 60 m²10%Junctionscold bridges at joinsFRONTBACKWHERE THE SECTION CUTSnext doorthis house12345678910THE JOBS, IN THE USUAL ORDER1 attic · 2 cavity wall · 3 internal wall · 4 external wall · 5 windows and doors · 6 heating controls7 heat pump · 8 solar water · 9 solar panels · 10 boiler
Where a semi-detached house built 1971–80 loses its heat: walls 32%Section through a semi-detached house built 1971–80, front to back. Share of the heat lost per degree of temperature difference, by element: walls 32%, windows 18%, air 17%, floor 11%, roof 10%, junctions 10%, doors 2%. Air (draughts, vents and chimneys) is estimated as the remainder. Arrow widths are to scale. Medians of 4,498 homes sold or let, assessed 2022–26. Numbered pins mark where each job acts: 1 attic, 2 cavity wall, 3 internal wall, 4 external wall, 5 windows and doors, 6 heating controls, 7 heat pump, 8 solar water, 9 solar panels, 10 boiler.SEMI-DETACHED HOUSE BUILT 1971–80 · SECTIONWalls32%Windows18%Doors2%Air17%Roof10%Floor11%Junctions10%12345678910THE JOBS, IN THE USUAL ORDER1 attic · 2 cavity wall · 3 internal wall4 external wall · 5 windows and doors6 heating controls · 7 heat pump8 solar water · 9 solar panels · 10 boilerELEMENTSHARE OF HEAT LOSSWallsU 1.10 · 89 m²32%WindowsU 2.80 · 21 m²18%Airdraughts, vents, chimney (est.)17%FloorU 0.64 · 60 m²11%RoofU 0.40 · 61 m²10%Junctionscold bridges at joins10%DoorsU 2.95 · 2 m²2%

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 ten 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
The numbers behind figure 1
ElementShare of heat lossMedian
Walls32.0%1.10 W per m² per degree, 89 m²
Windows17.6%2.80 W per m² per degree, 21 m²
Air (estimated)16.8%the remainder
Floor10.7%0.64 W per m² per degree, 60 m²
Roof10.5%0.40 W per m² per degree, 61 m²
Junctions10.2%cold bridges at joins
Doors2.2%2.95 W per m² per degree, 2 m²
A pair of pebble-dash semi-detached houses on a Louth street, low garden walls with railings, one car on the road, flat grey sky.

Pebble-dash semis in Blackrock, Co. Louth. Figure 1 cuts through a typical semi-detached house built in the 1970s.

Houses in St Fursey's Terrace, Blackrock · Eric Jones · CC BY-SA 2.0

The ten jobs, link by link

Each job with what SEAI's grant pays against SEAI's typical price for a semi-detached house, and the one number to know. Fabric first: that's the usual order. SEAI rule

01Fabric

Most heat leaves through the walls, roof, floor and windows. Fix these first and the heating has less to replace. Five jobs, usually done first.

02Air

Sealing draughts keeps heat in. A tighter house then needs planned fresh air to stay dry. No individual grant of its own.

03Heat

The heating only puts back what the house loses. A heat pump works best when the house loses less. Four jobs.

04Use

A BER is a standard calculation across all four stages. Your bills also depend on how you live. One job makes your own power.

Grants: SEAI, individual route, read on the dates shown · typical prices: SEAI median costs H1 2026, semi-detached or end-terrace

Only two jobs move a rating a full letter on their own

One letter on the new scale is 50 points. A heat pump moves the typical home 93; solar panels, 60.7. Our model

Figure 2Our model

A heat pump moves a BER nine times as far as new windows

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.

How far one job moves a BER: median gain in kWh/m²/yr where the job applies, homes sold or letMedian improvement to the BER from one job on its own, where it applies: 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 kWh per m² a year. One letter on the new scale (D, E or F) spans 50. Our model of each job on each certificate's own figures.MEDIAN BER GAIN FROM ONE JOB, kWh/m²/yrone letter on the new scale (D, E or F): 50Heat pump93 kWh/m²/yrSolar panels60.7Wall insulation46.7New windows10.4Attic insulation6.1Blocking chimneys2.4Draught-stripping0.4
How far one job moves a BER: median gain in kWh/m²/yr where the job applies, homes sold or letMedian improvement to the BER from one job on its own, where it applies: 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 kWh per m² a year. One letter on the new scale (D, E or F) spans 50. Our model of each job on each certificate's own figures.MEDIAN BER GAIN, kWh/m²/yrone letter (D–F) = 50Heat pump93Solar panels60.7Wall insulation46.7New windows10.4Attic insulation6.1Blocking chimneys2.4Draught-stripping0.4

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
The numbers behind figure 2
JobMedian gain, kWh per m² a year
Heat pump93
Solar panels60.7
Wall insulation46.7
New windows10.4
Attic insulation6.1
Blocking chimneys2.4
Draught-stripping0.4

Three jobs take a typical semi-detached house built 1971–1980 from D to B

Our model's cheapest route, at SEAI's typical prices, with the grants in force today. A group figure, not a quote for your house. Our model

Figure 3Our model

Grants pay €19,500 of a €28,685 job for a 1970s semi-D going from D to B

At SEAI’s median costs the route is €28,685; the grants in force take off €19,500, leaving €9,185, or €11,185 if there’s no fossil boiler to scrap.

Attic, Internal walls, Heat pump: grants pay €19,500 of a €28,685 jobThe work at SEAI median costs: attic €2,101, internal walls €9,843, heat pump €16,741, total €28,685. Grants: heat pump €12,500, scrappage €2,000 (only if a fossil boiler or storage heaters go), walls €3,500, attic €1,500: €19,500. You pay €9,185, or €11,185 without the conditional grant.€, SEAI MEDIAN COSTS AND GRANTS IN FORCE 3 OCT 2026ROUTE: OUR MODELAttic€2,101Internal walls€9,843Heat pump€16,741€28,685−€12,500heat pump−€2,000 scrappage*−€3,500walls−€1,500 attic−€19,500€9,185The workSEAI median costsGrantsSEAI, individual routeYou pay€11,185 withoutthe scrappage grant* Boiler scrappage: only if an oil, gas or solid-fuel boiler or storage heaters are removed.
Attic, Internal walls, Heat pump: grants pay €19,500 of a €28,685 jobThe work at SEAI median costs: attic €2,101, internal walls €9,843, heat pump €16,741, total €28,685. Grants: heat pump €12,500, scrappage €2,000 (only if a fossil boiler or storage heaters go), walls €3,500, attic €1,500: €19,500. You pay €9,185, or €11,185 without the conditional grant.€ · SEAI MEDIANS AND GRANTS, 3 OCTInternal wallsHeat pump€28,685−€19,500€9,185The workGrantsYou payJOBCOSTGRANTHeat pump + heating€16,741−€12,500Boiler scrappage*—−€2,000Internal walls€9,843−€3,500Attic€2,101−€1,500* only if a fossil boiler goes. Without it:you pay €11,185. Route: our model.

The left column stacks the jobs in our model's cheapest route to B for a semi-detached house built 1971–80 and rated D, at SEAI's January to June 2026 median costs: heat pump €16,741, internal walls €9,843, attic €2,101. The middle column is each SEAI grant on the individual route: heat pump €12,500, scrappage €2,000 (hatched: only if an oil, gas or solid-fuel boiler or storage heaters go), walls €3,500, attic €1,500. The right column is what's left to pay at those medians; a real quote will differ.

EstimateThe route is our model (data/transitions.json, /ber/d-to-b/semi-detached-1971-1980); costs are SEAI medians, grants the amounts in force since 29 Sep 2026.

Sources: fixmyber model route, 8 Sep 2026 · SEAI, Median costs of individual energy upgrades, Jan-Jun 2026 (H1 2026), 2026 · SEAI grant pages, transcribed in pipeline/inputs/grants_2026.csv, 3 Oct 2026

The numbers
The numbers behind figure 3
JobMedian costGrant
Heat pump€16,741€12,500
boiler scrappage (only if a fossil boiler goes)—€2,000
Internal walls€9,843€3,500
Attic€2,101€1,500
Total€28,685€19,500

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Updated · grants checked · BER file · prices SEAI H1 2026 · How we know · Corrections