300mm Attic Insulation Across the Midlands: 2026 Costs & €1,500 SEAI Grant

300mm Attic Insulation Prices & SEAI Grants (2026)

Includes 100mm between joists + 200mm cross-laid over joists, eaves vent trays, tank jacket, pipe lagging, electrical downlight hoods, and insulated hatch lid.

Why SEAI Inspects Eaves Ventilation & Tank Lagging (S.R. 54)

Rolling out 300mm of mineral wool on its own will fail an SEAI audit if the wool is pushed into the soffit eaves. Under S.R. 54, every SEAI-compliant attic upgrade includes:

• Continuous 50mm Eaves Ventilation Trays: Rigid plastic rafters trays keep a clear 50mm airway from the soffit vents into the roof space so winter condensation never forms on the underside of the roofing felt.
• Cold Water Storage Tank & Pipework Lagging: Because a 300mm ceiling blanket keeps heat inside the rooms below, the attic space above becomes much colder in winter. The cold water tank is insulated on its top and sides (leaving the area directly beneath the tank uninsulated so rising warmth prevents freezing) and all attic pipes are wrapped in closed-cell polyethylene lagging.
• Raised Loft-Leg Storage Boarding: Squashing 300mm wool under standard 100mm ceiling joists destroys half its R-value. If you want attic storage, 200mm Loft Legs or counter-battens raise the chipboard deck above the wool without compressing it.