Improving your BER (Building Energy Rating) is best done in a sensible order: fix the fabric first (insulation and airtightness), then upgrade controls and heating, and finally add renewables. Doing it in this sequence means every later step works with a warmer, tighter house — so your heat pump can be smaller and your bills lower.
This is the roadmap most Irish homes follow to climb from a typical C or D up toward A or B.
The improvement roadmap
Work top-to-bottom. Each step reduces the heat your home loses, which makes the next step cheaper and more effective.
| Step | Measure | Typical BER impact | Why it comes here |
|---|---|---|---|
| 1 | Attic insulation (100mm → 300mm) | 1–2 bands | Cheapest, fastest, biggest single win |
| 2 | Cavity or external wall insulation | 1–3 bands | Walls are the largest heat-loss surface |
| 3 | Airtightness & draught-proofing | 0–1 band | Stops warm air leaking out |
| 4 | Heating controls & zoning | 0–1 band | Cheap, improves how existing heat is used |
| 5 | Heat pump (oil/gas boiler → AWHP) | 2–4 bands | Big jump once fabric is sorted |
| 6 | Solar PV (3–4 kWp) | 1–2 bands | Adds on-site renewable generation |
A home that completes all six can often move from D1 to A2/A3.
Step 1 — Attic insulation first
The attic is where most homes leak the most heat, and it’s the easiest space to upgrade. Going from a thin 100mm layer up to the recommended ~300mm typically lifts a BER by one to two bands. It’s also grant-supported, which keeps the net cost low. See our attic insulation guide for what’s involved.
Step 2 — Walls
Walls are the biggest surface losing heat. If you have a cavity (most homes built from the 1940s on), cavity wall insulation is fast and relatively inexpensive. Solid-wall or older homes may need external wall insulation, which costs more but can shift a BER by two to three bands. Both are covered under SEAI insulation grants.
Step 3 — Airtightness
Once you’ve insulated, sealing draughts around doors, windows, attic hatches and service penetrations stops warm air escaping. It rarely moves a band on its own but it improves comfort and protects the gains from steps 1 and 2.
Step 4 — Heating controls
Upgrading to modern heating controls — programmable thermostats, zoning and time control — helps you use heat only where and when you need it. There’s an SEAI grant for heating controls of €700.
Step 5 — Heat pump
Once the fabric is right, swapping an oil or gas boiler for an air-to-water heat pump is the single biggest BER mover, often worth two to four bands because it replaces fossil-fuel heating with efficient electric heat. There’s a grant of €6,500 toward the unit. Check whether your home is heat-pump-ready in BER for a heat pump and heat pumps in older homes.
Step 6 — Solar PV
Finally, solar PV adds renewable generation that the BER methodology rewards, typically worth one to two bands for a 3–4 kWp array. The SEAI solar grant is capped at €1,800. See solar PV costs in Ireland.
Don’t forget the new assessment
Upgrades don’t change your certificate until a SEAI-registered assessor re-assesses the home and lodges a new BER. Book this only after all works are finished, so every improvement is captured at once. The individual BER assessment grant is €50.
How much does it cost — and what’s covered?
Most of these measures attract SEAI grants when done individually, or a higher level of support through a One Stop Shop. For a full picture of what’s available, see the SEAI grants guide and our BER ratings explainer.
Where to start
The smartest first move is a current BER, so you know your baseline and which measures will pay back fastest.
Check what grants you qualify for at /grants/check-eligibility/.
Source: SEAI, 12 June 2026 Source: SEAI, 12 June 2026