Home energy guide
Cavity wall insulation cost and grant in Ireland
A practical guide to cavity-wall insulation costs, suitability, potential grants and the assessment needed before work begins.
Last reviewed: September 2026
Indicative costs
HomePlanIQ uses seai completed energy-upgrade cost data for this guide, covering January to December 2025. Where a stored median is available, the displayed range applies the existing HomePlanIQ planning spread. These figures are planning information, not quotations or guarantees.
Published 2025 completed-project medians. A survey is required to confirm that the cavity is present, clear and suitable for filling.
Current SEAI grant position
For qualifying homes, the stored Individual Grant amounts are up to €1,800 for a detached house, €1,300 for a semi-detached home, €850 for a terraced home and €700 for an apartment. Higher stored amounts may apply in qualifying welfare-payment circumstances.
The grant depends on the current SEAI rules, property details, wall suitability and application requirements. It is a potential amount, not a guaranteed payment. See the official SEAI wall-insulation information.
Why the cavity needs an assessment
Not every wall contains a clear, continuous cavity that can be filled. The cavity must be present, accessible and suitable, and moisture exposure, construction details and previous work can change the answer. Cavity block construction must not be assumed to be a conventional fillable cavity.
A survey or installer assessment should confirm the wall build-up and condition before an application or installation is treated as settled.
Possible additional work
Access, local repairs, vents, openings, damp-related issues and making good can affect the scope. If cavity filling is unsuitable, external wall insulation or internal wall insulation may be more appropriate, subject to assessment.
Compare the available wall-upgrade routes and other measures on the upgrade guides hub.
Plan this upgrade with the rest of your project
Use the HomePlanIQ calculator to estimate this work alongside other home improvements. It provides indicative project ranges and potential grant information, not an exact contractor quotation.
Open the HomePlanIQ calculatorSources and methodology
Cost figures use the existing HomePlanIQ source record for Cavity wall insulation, checked on 2026-09-09. Grant information uses the existing SEAI - Wall insulation record, checked on 2026-09-09. Confirm current rules and application requirements with the official SEAI source.
For more detail on HomePlanIQ cost ranges and potential grants, read the Methodology & data sources page or browse all upgrade guides.