Wall Insulation Ireland: Cavity, External & Internal

Last updated: August 2026
Your walls are the biggest surface in your home, and in an older house they can leak up to a third of your heat. That makes wall insulation the single most powerful upgrade for your BER rating – often enough to jump a whole grade band. The catch is that the right method, and the cost, depend entirely on how your walls were built. In 2026 the SEAI grants for wall insulation in Ireland are the most generous of any insulation measure, reaching up to €8,000 for external work.
This guide explains the three types of wall insulation, what each costs, how much the grant is worth, and how to choose the right one for your home.

⚡ Quick Summary

🌿 The grants: up to €1,800 for cavity wall, €4,500 for internal (dry-lining) and €8,000 for external wall insulation on a detached home.
🌿 The cheapest win: if you have cavity walls, pumping them full is quick, affordable and often almost fully covered by the grant.
🌿 The biggest impact: external wall insulation transforms an old solid-wall home, but it is the most expensive option (€10,000 to €25,000 before grant).
🌿 Step one: find out whether you have cavity walls or solid walls – it decides everything.
🌿 Golden rule: get grant approval and a wall survey before any work begins.

🧱 Cavity, Solid or Timber? Know Your Walls First

Before you look at grants or prices, you need to know what kind of walls you have, because it determines your options:
🌿 Cavity walls (most homes built from the 1940s onwards): two “leaves” of block with a gap between them. That gap can be pumped full of insulation quickly and cheaply – the best-value option by far.
🌿 Solid walls (older homes, typically pre-1940s, and some later): no cavity to fill, so you must add insulation either on the inside (dry-lining) or the outside (external wall insulation).
🌿 Timber-frame walls: assessed individually; a surveyor will advise the right approach.
A quick way to tell: cavity walls are usually around 300mm thick, while solid walls tend to be thinner. An SEAI-registered contractor will confirm with a survey before any work.

💶 The SEAI Wall Insulation Grants 2026

There are three separate grants, one for each method. Amounts depend on your home type:

🔹 Cavity Wall Insulation

🌿 Detached: up to €1,800
🌿 Semi-detached / end of terrace: around €1,300
🌿 Mid-terrace: around €850
🌿 Apartment: around €700
🌿 Qualifying welfare recipients: higher cavity rates – up to €2,300 for a detached home

🔹 Internal (Dry-Lining) Wall Insulation

🌿 Detached: up to €4,500
🌿 Semi-detached / end of terrace: around €3,500
🌿 Mid-terrace: around €2,000
🌿 Apartment: around €1,500

🔹 External Wall Insulation

🌿 Detached: up to €8,000
🌿 Semi-detached / end of terrace: around €6,000
🌿 Mid-terrace: around €3,500
🌿 Apartment: around €3,000
Grant amounts are reviewed periodically, so use these as a guide and confirm the current figure on seai.ie. As with all SEAI home energy grants, homes on a qualifying welfare payment may get the work done free through the Warmer Homes Scheme.

🔹 Who Qualifies

🌿 Your home must have been built (and occupied) before 2011.
🌿 Work must be done by an SEAI-registered contractor.
🌿 You must apply and be approved before work starts.
🌿 Cavity walls need a cavity survey first to confirm they are suitable.
🌿 A BER assessment is part of the process (the SEAI contributes €50).

🛠️ What Does Wall Insulation Cost in Ireland?

The three methods sit at very different price points – which is why knowing your wall type matters so much:
🌿 Cavity wall insulation: typically €700 to €1,800 for a whole house. With the grant, many homeowners pay little or nothing. Fast (often a single day) and non-disruptive.
🌿 Internal dry-lining: typically €4,000 to €12,000 depending on house size. Cheaper than external, but it is disruptive (rooms are done one at a time) and slightly reduces room dimensions.
🌿 External wall insulation: typically €10,000 to €25,000 before the grant. The most expensive, but the most effective – it wraps the whole house, eliminates cold bridges and refreshes the exterior finish.

🔍 Which Type Is Right for Your Home?

🌿 You have cavity walls: pump them. It is the clearest win in home energy – cheap, quick, grant-covered and effective. Do this before anything else.
🌿 You have solid walls and budget is tight: internal dry-lining is the more affordable route, though you lose a little floor space and it means redecorating.
🌿 You have solid walls and want the best result: external wall insulation delivers the biggest performance jump and looks like a fresh render job when finished. Check first whether it affects your home’s appearance or needs planning input, especially on a terrace or a protected structure.
Whichever route you take, walls are usually the highest-impact step in a full home retrofit, and they pair naturally with a heat pump – a well-insulated house lets a heat pump run at its most efficient.

⚠️ Common Mistakes to Avoid

🌿 Filling unsuitable cavities – homes very exposed to driving rain, or with damaged walls, may not be suitable for cavity fill. That is what the survey is for; never skip it.
🌿 Ignoring damp first – fix any existing damp or water ingress before insulating, or you will seal the problem in.
🌿 Creating cold bridges – patchy or partial insulation leaves cold spots where condensation forms (our ventilation guide covers the moisture side). Read our guide to thermal bridging to understand why full, continuous coverage matters.
🌿 Starting before approval – as with every grant, work begun before approval is not eligible.
🌿 Overlooking the exterior on external insulation – it changes how your house looks and meets the ground, so plan finishes, sills and door thresholds with your contractor.

❓ Frequently Asked Questions About Wall Insulation

🔹 How much is the SEAI wall insulation grant in 2026?

For a detached home, up to €1,800 for cavity wall, €4,500 for internal dry-lining and €8,000 for external wall insulation. Amounts scale down for smaller homes and apartments – confirm your figure on seai.ie.

🔹 How do I know if I have cavity or solid walls?

Cavity walls (most homes from the 1940s on) are usually around 300mm thick with a gap inside; solid walls are typically thinner. An SEAI-registered contractor confirms it with a survey before any work.

🔹 How much does cavity wall insulation cost?

Typically €700 to €1,800 for a whole house, and with the grant many homeowners pay very little. It is usually finished in a single day.

🔹 Is external or internal wall insulation better?

External performs better and wraps the whole house, but costs €10,000 to €25,000 before grant. Internal dry-lining is cheaper but reduces room size slightly and is more disruptive. External suits solid-wall homes wanting the biggest improvement.

🔹 Which wall insulation gives the best value?

Cavity wall insulation, by a distance – if your home has fillable cavities. It is the cheapest, fastest and most grant-covered option, and it is the first wall upgrade you should consider.

🔹 Do I need a BER for a wall insulation grant?

Yes. A BER assessment is part of the process, and it confirms how much your rating has improved afterwards.

🔹 What should I insulate first, walls or attic?

Do the attic first – it is cheaper and quicker – then move to the walls, which are the next biggest source of heat loss.

📚 Related Guides

🌿 Attic Insulation
🌿 Home Ventilation
🌿 BER Rating
🌿 BER Cert Cost
👉 All guides and calculators

Climate Jargon Buster is an independent resource providing plain-English information on climate, energy and sustainability topics for an Irish audience. Costs are indicative 2026 figures and vary by home; grant amounts are correct as of August 2026 and are set by the SEAI. For official grant terms and to find a registered contractor, visit seai.ie. This site is not affiliated with SEAI – always check the official website for current figures.