Cavity wall insulation and SEAI grant glossary

Bonded Polystyrene Bead (EPS)

Expanded polystyrene spheres injected into a masonry wall cavity together with a water-based PVA bonding adhesive, curing into a self-supporting, water-resistant insulating matrix.

Borescope Cavity Inspection

A pre-works optical survey through a 12 mm test hole in the mortar bed to verify clear cavity width, wall tie condition, mortar snots, and existing partial-fill boards.

Clear Cavity Width (50 mm Minimum)

The unobstructed air gap between the inner and outer masonry leaves required under NSAI Agrément certificates before bonded bead can be pumped.

Cold Bridging (Thermal Bridge)

A pathway of higher heat loss through dense concrete lintels, window reveals, solid jambs, or mortar droppings where insulation continuity is interrupted.

Condensation Risk & Interstitial Damp

Moisture vapour condensing inside the wall structure when warm indoor air meets a cold masonry surface without adequate room ventilation under TGD Part F.

Driving Rain Exposure (IS EN ISO 15927-3)

The wind-driven rain index across Ireland used to determine cavity fill suitability; bonded EPS bead is certified for severe Atlantic exposure zones where loose mineral wool can hold moisture.

Dwelling Energy Assessment Procedure (DEAP)

SEAI's official calculation methodology used by registered BER assessors to compute a home's primary energy consumption and carbon rating before and after cavity pumping.

MPRN (Meter Point Reference Number)

The 11-digit ESB Networks electricity meter identifier printed on household energy bills, used by SEAI to verify the dwelling's build date and past grant history.

NSAI Agrément Certificate

Formal Irish technical certification issued by the National Standards Authority of Ireland confirming an insulation material and injection method meet Irish Building Regulations.

Open-Cell vs Closed-Cell Bead

Expanded polystyrene beads have a closed cellular structure that does not wick liquid water across a cavity, while graphite coatings lower radiant heat transfer inside the bead.

Post-Works BER (Building Energy Rating)

The compulsory energy assessment carried out after cavity insulation is completed and logged to the national register before SEAI releases the cash grant.

Rubble-Filled Base & Mortar Snots

Hardened mortar droppings resting on wall ties or at the bottom dpc tray inside an older cavity, which can deflect injected bead or channel damp toward the inner leaf if not cleared.

Sub-Floor Periscope & Room Wall Vents

Baffled core-drilled wall vents and telescopic sub-floor vents required under TGD Part F and NSAI SR 54 so insulated rooms and suspended timber floors remain ventilated.

Thermal Conductivity (Lambda Value)

The rate at which heat passes through a material, measured in W/mK; platinum grey graphite EPS bead achieves 0.033 W/mK compared with 0.038 to 0.040 W/mK for white bead.

U-Value (Thermal Transmittance)

The heat loss rate through one square metre of wall per degree of temperature difference (W/m²K); pumping an empty 100 mm cavity typically drops wall U-value from 1.68 to around 0.33 W/m²K.

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