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Both external wall insulation and internal wall insulation cut heat loss and lower your bills, but they suit different homes, budgets and situations. External wall insulation, often called the wrap, fixes insulation to the outside of your walls and covers it with a new render. Internal wall insulation, also called dry lining, fixes insulated boards to the inside face of your external walls.
This guide sets the two side by side so you can see which fits your home.
First Check What Kind of Walls You Have
Before comparing the two, it helps to know what your walls are made of, because that often decides your options.
- Cavity walls, common in homes built from the 1940s to the early 2000s, have a gap between two leaves of blockwork. Where the cavity is clear, pumping it full of insulation is the cheapest option, and external or internal insulation becomes an extra step rather than a necessity.
- Solid walls, typical of homes built before the 1940s, have no cavity to fill. For these homes the only way to insulate the walls is external or internal.
One quick guide is thickness. Cavity walls are usually around 300mm thick, while solid walls tend to be thinner. If you are not sure, a survey will confirm it. If you own an older property, knowing what to check before renovating an older Irish home is a useful companion.
External Wall Insulation Explained
External wall insulation wraps the outside of your home in insulation board and finishes it with a weatherproof render. It is the most effective option, because it covers the whole building and removes the cold bridges where heat escapes at floors, corners and around openings. It also refreshes the look of the house and does not touch your interior or reduce room sizes.
Costs run to roughly €100 to €180 per square metre, or about €10,000 to €25,000 for a typical house before the grant. External work is usually finished in two to four weeks with little disruption inside. For a fuller breakdown, see our guide to external wall insulation costs.
Internal Wall Insulation Explained
Internal wall insulation, or dry lining, fixes insulated plasterboard to the inside face of your external walls. It costs less than external work and does not change how the house looks from outside, which makes it a common choice for protected structures or where planning limits an exterior change.
Costs are lower, at roughly €4,000 to €12,000 before the grant depending on house size. There are two trade-offs. Rooms are done one at a time and need redecorating, and each insulated wall loses about 50mm to 100mm of floor space. Cold bridges at floors and party walls can also remain unless they are carefully detailed.
External vs Internal Wall Insulation at a Glance
| Factor | External (the wrap) | Internal (dry lining) |
| Typical cost before grant | €10,000 to €25,000 | €4,000 to €12,000 |
| SEAI grant by house type | €3,000 to €8,000 | €1,500 to €4,500 |
| Thermal performance | Highest, wraps the whole home | Good, but some cold bridges remain |
| Disruption | Low, work is outside | High, room by room inside |
| Floor space lost | None | 50mm to 100mm per wall |
| Exterior appearance | Changes, with a fresh render | No change |
| Planning permission | May be needed in some cases | Not normally needed |
| Best for | Solid-wall homes and full retrofits | Tight budgets, protected fronts, phased work |
Grant amounts depend on your house type and the current SEAI rates. Confirm your figure at seai.ie or ask us to check it during a survey.
How SEAI Grants Compare
Both measures qualify for SEAI grants under the Better Energy Homes scheme, and external wall insulation carries the larger grant. As things stand in 2026, external grants run from €3,000 for an apartment up to €8,000 for a detached house, while internal dry lining grants run from €1,500 up to €4,500. Amounts depend on your house type, so it is worth confirming your figure on seai.ie.
To qualify, your home must have been built and occupied before 2011, the work must be done by an SEAI-registered contractor, and you must be approved before any work starts. All external walls have to be insulated, since a partial job does not qualify. Clarcon carries out external wall insulation across Dublin and the surrounding counties and manages the grant paperwork with you.
Which One Is Right for Your Home
There is no single right answer, only the right fit for your home and budget. External wall insulation is usually the better choice if you have solid walls, want the biggest drop in heat loss, plan to refresh the exterior anyway, or cannot afford to lose any room space. It also avoids moving out or clearing rooms.
Internal insulation tends to win where the budget is tighter, where the front of the house must stay as it is, or where you would rather tackle one room at a time. On a protected structure, it is often the only option allowed.
Where you have a clear cavity, pumping it first is the cheapest way to cut heat loss, and you can still add external insulation later for a deeper upgrade. Only a survey will settle it for certain, since it weighs your wall type, your budget and the result you want.
Get Expert Advice on Wall Insulation in Dublin
Choosing between external and internal insulation is easier with someone who has seen the walls. Clarcon specialises in external wall insulation and has 17+ years across building and energy-upgrade work in Dublin, Kildare, Louth, Meath and Cavan. If you are weighing up your options as part of a wider home renovation, we can assess your home, explain what suits it and handle the SEAI grant. Call 01 437 0645 or use the online quote form to book a survey.
