External wall insulation and SEAI grant glossary
Plain-English definitions of the 15 ETICS, U-value, render and SEAI grant terms you will see on external wall insulation quotes.
Free, no obligation. One registered contractor prices it, not five.
- 15terms defined A to Z
- 0.18 W/m²Ktarget wall U-value
- €8,000detached grant
- €6,000semi-D grant
A to Z of external wall insulation and grant terms
Below-DPC Plinth Insulation
High-density, water-resistant extruded polystyrene (XPS) fitted from the starter track down to ground level to reduce cold bridging at the ground-floor slab junction.
ETICS (External Thermal Insulation Composite System)
A complete, tested exterior wall wrap kit comprising adhesive mortar, insulation boards, mechanical fixings, glass-fibre reinforcing mesh, basecoat, primer, and breathable topcoat render certified as a single system.
Glass-Fibre Reinforcing Mesh
Alkali-resistant woven mesh embedded into the wet polymer basecoat over the insulation boards to absorb thermal expansion and prevent hairline cracking in the finished render.
Grey Expanded Polystyrene (EPS)
Graphite-enhanced rigid insulation board commonly used in Irish external wall wraps. At a thermal conductivity around 0.031 W/mK, a 100 mm to 150 mm board reaches the 0.18 W/m²K target at an economical cost.
Mechanical Dowel Fixings
Insulated-head pins drilled through the insulation boards into the structural masonry behind, working alongside the adhesive mortar bed to resist wind suction loads across the facade.
Mineral Wool (Rockwool) Slab
Non-combustible dual-density stone wool insulation board used in external wraps where high vapour permeability, acoustic damping, or Euroclass A1 fire performance near boundaries is required.
NSAI Agrément Certificate
Formal certification issued by the National Standards Authority of Ireland confirming that a specific external wall insulation system is engineered and tested for Irish wind-driven rain and exposure zones.
Roof Eaves & Verge Extension
Joinery and roofing work required when adding 120 mm+ of external insulation and render would otherwise project past shallow existing soffits, fascias, or gable verges.
Second Wall Measure Rule
The SEAI policy update allowing homes that previously received a cavity wall or internal dry-lining grant to apply for an external wall insulation grant where the earlier measure no longer brings the wall to modern thermal standards.
Silicone Thin-Coat Render
A water-repellent yet vapour-permeable coloured topcoat applied over the cured basecoat, shedding Irish rain while allowing trapped moisture in the masonry wall to evaporate outward.
Sill Extension / Oversill
A deeper replacement uPVC, aluminium, or stone-effect window sill fitted over or in place of the original concrete sill so rainwater drips well clear of the newly thickened external wall face.
Starter Track (Base Profile)
An aluminium or uPVC channel fixed horizontally above the damp-proof course (typically 150 mm above ground level) that supports the bottom row of insulation boards and sheds rainwater away from the plinth.
Tax Clearance Certificate (eTC)
Electronic confirmation from Revenue required by SEAI whenever a homeowner's combined grant payments exceed €10,000 within a twelve-month period.
Wall U-value of 0.18 W/m²K
The maximum thermal transmittance permitted by SEAI after external wall insulation is fitted. Achieving 0.18 W/m²K or lower typically cuts heat loss through solid or hollow-block masonry walls by 70% to 85%.
Window Reveal Return
Thinner high-performance insulation board (typically 20 mm to 30 mm phenolic or XPS) fitted into the jambs and head around windows and doors so heat cannot bypass the main external wrap at openings.
Your grant against your walls
Four quick taps. You see your grant, your wall, what a job that size typically costs and what's left. Your number is only asked for at the end, if you want a price.
An average semi-detached house: about 91 m² of outside wall, a typical job of about €23,200, the €6,000 grant, so about €17,200 left to pay.
How this is worked out
The grant is SEAI's fixed amount for your house type. The wall area is the median outside wall on the BER register for homes of your type built before 2011, or the smaller or larger quarter if you picked those. The typical job is what grant-funded external insulation typically costs for your house type, scaled to that wall. Your contractor prices your house after a look: it's a guide to plan with, never a quote. SEAI decides every grant.
Questions people ask
How thick is an SEAI-compliant external wall insulation wrap?
Most Irish homes require between 100 mm and 150 mm of graphite-enhanced EPS insulation—plus roughly 8 mm to 10 mm of reinforced basecoat and silicone topcoat—to bring an uninsulated solid or hollow-block wall down to the required 0.18 W/m²K U-value.
Do I need planning permission to wrap the outside of my house?
External wall insulation on the side and rear elevations is generally exempt from planning permission in Ireland. If the wrap alters the front elevation finish on a terraced street, sits inside an Architectural Conservation Area, or involves a Protected Structure, check with your local authority planning office first.
What happens to pipes, meter boxes, flues, and satellite dishes on the wall?
Your SEAI-registered contractor extends rainwater downpipes, soil vents, outside taps, and alarm sounders outward to sit flush on the new face. Boiler flues and gas or ESB meter boxes must be extended or recessed by a registered RGI gas installer or Safe Electric electrician.
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Your grant against your walls
Four taps to your grant, your wall and what's left. Then, if you want, one SEAI-registered external insulation contractor who covers your county rings with a price.