bungalowExternal Insulation Dublin

External vs Internal vs Cavity Wall Insulation — Which Is Right for Your Home?

There are three ways to insulate a wall — internal, external or cavity wall insulation — and the right one depends on how your home is built, not personal preference. Here's an honest comparison of all three, including when external insulation (our specialty) isn't actually the best fit.

Ask Which Fits Your HomeCall +353 1 265 8494

Side-by-Side Comparison

Figures are typical Irish market ranges — your survey gives you an exact figure.

Cavity Wall InsulationInternal Wall InsulationExternal Wall Insulation
Best suited toHomes built post-1930s with a cavity (gap) between two wall leavesSolid-wall homes where the exterior can't be altered — protected structures, terraced return walls, apartmentsSolid-wall or early cavity Dublin homes built before 2011 wanting the biggest thermal and BER improvement
Typical costTypically €800-€1,800 for a standard 3-bed semiTypically €4,000-€10,000 depending on rooms treatedTypically €8,500-€26,000 depending on house size, before grant
DisruptionA few hours — small holes drilled, insulation pumped in, holes filledRoom-by-room — furniture moved, skirting/sockets refitted, redecoration needed after2-4 weeks of exterior scaffolding — you stay living in the house throughout
Thermal improvementModest improvement — depends heavily on cavity condition and widthStrong improvement, but doesn't remove cold bridging at floor and ceiling junctions as fully as externalBest improvement of the three — eliminates cold bridging and wraps the whole thermal envelope
Appearance / spaceNo visible change to the exteriorNo exterior change, but loses internal floor area (40-100mm per wall) and disrupts room finishesExterior render is fully renewed, in a colour of your choice — no internal floor space lost
SEAI grantSEAI grant available, typically up to €1,500SEAI grant available, typically up to €5,600SEAI grant available, up to €8,000

Cavity and internal wall insulation figures are general Irish market guidance for context — we specialise in external wall insulation and don't install the other two. See our full external wall insulation cost guide for exact figures on that option.

How Pumped Cavity Wall Insulation Works

Cavity wall insulation is sometimes called “pumped” insulation because that's literally how it's installed — an insulation material (usually bonded bead or mineral wool) is pumped into the cavity gap between the inner and outer wall leaves through small drilled holes, filling the gap from the inside out.

It only works if your home actually has a cavity to fill — a gap of roughly 50-100mm between two masonry leaves, standard on most Irish homes built from the 1940s onward. Solid-wall homes have nothing to pump into, which is why external or internal insulation is the only option for older Dublin properties.

1
Small holes drilled
10-15mm holes drilled in a grid pattern across the outer wall leaf, roughly 1m apart.
2
Material pumped in
Bonded bead or mineral wool is pumped through each hole under pressure, filling the cavity completely.
3
Holes filled and blended
Each hole is capped and colour-matched to the existing wall finish, leaving no visible trace.
4
Done in hours, not weeks
A standard 3-bed semi is usually finished in a single day — no scaffolding, no internal disruption.

Which One Actually Fits Your Home?

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Standard cavity-wall home, tight budget

If your home was built from the 1940s onward and has a cavity, pumped cavity fill is the cheapest, fastest first step — though the thermal gain is smaller than external insulation.

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Protected structure or conservation area

If the exterior can't be altered, internal wall insulation is often your only option, room by room.

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Solid-wall or early cavity Dublin home

Most Dublin homes built before 2011 fall into this category. External wall insulation delivers the biggest BER and comfort improvement without losing any internal floor space — this is exactly what we specialise in.

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Want the maximum SEAI grant and BER jump

External wall insulation carries the largest SEAI grant (up to €8,000) because it typically delivers the largest efficiency improvement of the three options.

If External Insulation Fits, We're the Specialists

We only install external wall insulation — no subcontracting, no diversification — which means deep expertise on the option that suits most pre-2011 Dublin homes. See the honest disadvantages too, or check SEAI grant amounts for your property type.

Common Questions

What's the difference between external and internal wall insulation?expand_more
External wall insulation is fixed to the outside of the house and finished with a new render — it doesn't reduce internal room size and removes cold bridging most effectively. Internal wall insulation (dry-lining) is fixed to the inside face of external walls, which is cheaper and avoids scaffolding but eats into floor area and disrupts every room it's applied to.
Is cavity wall insulation better than external wall insulation?expand_more
Not better — different. Cavity wall insulation only works if your home already has a cavity (gap) between two wall leaves, usually homes built from the 1930s onward. It's cheaper and quicker, but the thermal improvement is smaller than external insulation and it does nothing for a solid-wall home, which most pre-1940s Irish houses are.
How do I know if my house has cavity walls or solid walls?expand_more
As a rough guide, homes built before the 1930s in Ireland are usually solid wall (brick or stone, typically 225-350mm thick with no gap), while most homes from the 1940s onward have a cavity. A site survey confirms this immediately — it's the first thing we check.
Can I get an SEAI grant for internal or cavity wall insulation?expand_more
Yes, SEAI grants are available for all three approaches — up to roughly €1,500 for cavity wall, €5,600 for internal wall, and €8,000 for external wall insulation on a detached home, depending on dwelling type. External wall insulation carries the largest grant because it typically delivers the biggest efficiency and BER improvement.
Why do you only offer external wall insulation, not internal or cavity?expand_more
We specialise exclusively in external wall insulation because it's the highest-impact option for the solid-wall and early-cavity Dublin housing stock we work on every day, and specialising means deeper expertise and fewer mistakes on the technique that matters most. If your home is a straightforward post-1960s cavity-wall build, a cavity-fill specialist may be a faster, cheaper first step.
Which type of insulation is best for a period or protected home?expand_more
Internal wall insulation is often the only option for protected structures or homes in an Architectural Conservation Area, since the exterior render and character can't be altered without planning consent. Where external insulation is permitted — many Dalkey and Blackrock streets outside the strictest conservation zones — it usually delivers a bigger thermal upgrade for the same disruption.
What is pumped cavity wall insulation?expand_more
Pumped cavity wall insulation is bonded bead or mineral wool blown into the gap between a home's two wall leaves through small drilled holes, filling the cavity from the inside out. It's the cheapest and fastest of the three options, usually finished in a single day, but it only works on homes that actually have a cavity to fill.
Is cavity wall insulation common in Dublin homes?expand_more
Yes, for homes built from the 1940s onward — most post-war Dublin estates and later developments have a cavity wall and can be pumped. Older Dublin housing stock (Georgian, Victorian and early-1900s terraces common in the city and in areas like Dalkey) is typically solid wall, which cavity fill can't help — that housing needs external or internal insulation instead.

Not Sure Which Option Suits Your Home?

A free site survey tells you exactly what your wall type is and which insulation approach makes sense — no obligation either way.

Book a Free SurveyCall +353 1 265 8494