What BER rating can insulation improve?
A BER rating is a measure of energy use per square metre per year, from A1 down to G. Insulation moves it, sometimes dramatically — but which measure moves it most depends on where your house is losing heat, and no fabric upgrade alone will take a G to an A.
What the bands mean
The scale runs on kilowatt-hours per square metre per year. Lower is better. A new house built to current standards lands around A2 or A3. A great deal of Ireland's existing stock sits between D and F.
The bands are not evenly spaced in effort. Moving from F to D is far easier than moving from C to B, because the early gains come from cheap measures and the later ones require heating and ventilation changes as well as fabric.
What each measure typically contributes
Rough guidance, not a promise — the actual figure depends on your house:
- Attic insulation on an uninsulated roof: often one band, sometimes more on a bungalow.
- Cavity wall insulation: commonly one to two bands where the cavity is empty.
- External or internal wall insulation on a solid wall: frequently two or more bands, because you are addressing the largest single loss.
- Windows and doors: usually less than people expect on their own, but they matter for comfort and draughts.
Combining measures is where the real movement happens. Wall and attic together routinely take a D-rated house into the C band, and sometimes into B.
Why a G-rated house will not reach A with insulation alone
The A bands require very low energy use overall, and that means the heat source matters as much as the fabric. A house with excellent insulation and an old oil boiler will not reach A, because the rating accounts for how the remaining heat is generated.
That is not an argument against insulating. Insulating first is the correct order — there is no sense sizing a new heating system for a house that is still leaking heat. But it is worth knowing where the ceiling is before you set a target.
Getting the rating confirmed
A BER assessment after the work is required to close out an SEAI grant claim, so you will have a confirmed figure regardless. The assessor surveys the house and produces the certificate; the improvement is whatever the survey finds, not what anyone promised beforehand.
Common questions
Wall and attic insulation together commonly move a D-rated house into the C band. Solid-wall properties starting at E or F often gain two or more bands because the walls are such a large share of the loss.
Yes. A BER assessment after the work is completed is required to close out the claim.
Almost certainly not. The A bands account for how the remaining heat is generated, so the heating system matters as well as the fabric.
It is a required disclosure on any sale or letting, and it affects running costs, which buyers increasingly price in. We would not put a figure on it.
Usually wall insulation, because walls account for roughly 40% of heat loss. Attic insulation gives the best return per euro spent.
Want a figure for your own house?
A measured survey gives you the actual cost and the grant that applies. €100, refunded in full when you order.
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