What order should I retrofit my home?
Getting the order right saves you money and protects your grants. Get it wrong and you could lose grant eligibility or end up with an oversized heat pump that costs more to buy and run.
“Fabric first” — insulate before heating
This is not just good advice — it is how the SEAI grant rules work. Most heating and window grants require your home to meet an insulation standard first. If you skip insulation and go straight to a heat pump, you may not qualify for the grant, and you will need a bigger, more expensive pump to heat a leaky house.
Insulation first
Start with attic and wall insulation. This is the cheapest step, SEAI grants cover roughly 80% of the cost, and it makes the biggest difference to comfort and bills. It is also required before you can qualify for most other grants.
Attic insulation is the quickest win — typically €800–€2,500 with a grant of up to €1,500. Most homes get this done in a day.
Wall insulation depends on your wall type. Cavity wall insulation is the cheapest (€1,000–€2,500, grant up to €1,700). External wall insulation costs more (€8,000–€18,000) but has higher grants (up to €6,000) and is the most effective for older solid-wall homes.
New from March 2026: You can now do cavity wall insulation first and add external wall insulation later as a second wall measure. Previously you could only claim one wall insulation grant. This makes it easier to phase the work and spread the cost.
Heat pump and/or windows, once insulation is done
Once your home is properly insulated, you can move to the heating system and windows. These grants have fabric requirements — your home must meet certain insulation standards before you qualify.
Heat pump grant (up to €6,500): Your home must have a Heat Loss Indicator (HLI) of 2.0 W/K/m² or below. Homes built before 2005 almost always need insulation first to meet this. Insulating first also means you need a smaller, cheaper heat pump that runs more efficiently — saving you money on the unit and on running costs.
Windows grant (up to €4,000): Your home must meet a fabric standard — either an HLI of 2.3 or better, or your attic and walls must be rated Good or Very Good on the BER. Again, insulation first.
Why this order matters: If you install a heat pump in a poorly insulated home, you will need a 16kW unit instead of a 9kW unit. That costs €3,000–€5,000 more to buy, uses more electricity, and heats the home less effectively. Insulate first, size the pump second.
Solar PV — any time
Solar panels can be installed at any stage. The SEAI solar PV grant (up to €1,800) is standalone — it has no insulation or fabric requirement. You do not need to do a full retrofit or go through a One Stop Shop.
Many homeowners add solar first because it starts saving money immediately, or last because they want to size the system to match their new heat pump. Either approach works — the grant is the same.
You do not need to do it all at once
You can phase the work over 2–3 years, claiming separate SEAI grants each time. Many homeowners do attic insulation in year one, wall insulation in year two, and a heat pump in year three. Each stage has its own grant application.
The important thing is the order — insulation first, heating second, solar any time.
What happens if you do it in the wrong order?
- •You may not qualify for the heat pump grant if your home does not meet the HLI 2.0 fabric standard
- •You may not qualify for the windows grant if your attic and walls are not insulated
- •You will pay more for an oversized heat pump that works harder in a leaky house
- •Your running costs will be higher because the heat pump is fighting heat loss
- •You may need to retrofit the insulation later anyway — paying twice for disruption
Your home's exact requirements depend on its current condition and BER. A registered contractor or BER assessor can confirm what your home needs. Always check current rules at seai.ie. Last verified June 2026.
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Last verified: 2026-06-01