Deep Retrofit
A whole-house energy upgrade - insulation, heating, windows and ventilation together - aimed at jumping several BER bands in one project, typically to a post-works BER of B.
Rather than a single measure like attic insulation or a standalone heat pump, a deep retrofit bundles the building fabric (insulation, airtightness, windows), the heating system (usually a heat pump) and ventilation into one coordinated project, aimed at a step-change in BER rather than an incremental one. It is normally delivered through a One Stop Shop. The current SEAI target for the One Stop Shop route is a post-works BER of B, or a heat pump plus a 100 kWh/m²/yr reduction in primary energy demand - a simpler bar than the old B2 sub-band under the pre-2026 15-band scale.
A deep retrofit is the largest single home-energy job a homeowner is likely to do, and it bundles multiple trades - insulation, heat-pump/M&E, electrical, ventilation - into one procurement, so a single deep-retrofit lead can be worth several single-measure jobs combined.
PlanningLeads' free Home Energy & Grant Report models whether a home is a deep-retrofit candidate from its age, current BER and heating type, and estimates the combined SEAI grant available and the resulting BER uplift.
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Common questions
A single measure - attic insulation or a solar array on its own - isn't a deep retrofit. A deep retrofit combines fabric, heating and ventilation works in one project to jump multiple BER bands at once.
Under the current One Stop Shop route the target is a post-works BER of B (previously the B2 sub-band under the older scale), or an equivalent heat-pump-plus-100kWh/m²/yr primary-energy reduction.
Not necessarily, but a One Stop Shop is the main SEAI-backed route for coordinating a deep retrofit end to end, including the bundled grant.
This is a plain-English summary, not legal advice. Planning rules carry conditions and exceptions - always verify a specific case against the official source or a planning professional before acting.