Floor insulation cuts cold draughts at ground level and improves comfort, though floors lose less heat than walls or the roof. In Ireland it is grant-supported through the One Stop Shop route, and it is usually best done when floors are already being lifted or replaced.
Why insulate the floor?
Ground floors are typically responsible for around 10–15% of heat loss in an older home — less than walls or the attic, but enough to leave rooms feeling cold underfoot. Insulating reduces draughts, lifts the floor surface temperature, and helps a deep retrofit reach its overall BER target. Because the saving per euro is lower than for attic or wall measures, floor insulation rarely tops the priority list on its own — but it is well worth bundling into a wider upgrade.
The two main methods
How a floor is insulated depends entirely on what kind of floor you have.
Suspended timber floors
Common in older houses, these are timber boards on joists with a ventilated void beneath. They are insulated by:
- Lifting the floorboards, or working from below where there is a cellar or crawl space
- Fitting insulation (mineral wool or rigid board) between the joists, held up on netting or battens
- Adding a breathable membrane and reinstating the boards
The void must stay ventilated — blocking airbricks to keep heat in causes condensation and rot in the joists. This method is moderately disruptive if done from above, as rooms must be cleared and floors lifted.
Solid (concrete) floors
Found in newer homes and ground-floor extensions, solid floors are harder to upgrade. Options are:
- Insulating over the existing slab with rigid boards and a new screed or floating floor — this raises the floor level, so doors and skirtings need adjusting
- Digging out and re-laying with insulation below a new slab — the most thorough but most disruptive and expensive approach, only practical during major renovation
Because of the disruption, solid-floor insulation is almost always done as part of a larger project rather than as a stand-alone job.
Typical cost and disruption
Indicative installed costs, which vary a lot by site:
| Floor type | Typical cost | Disruption |
|---|---|---|
| Suspended timber (from below) | €20–€40 / m² | Low–moderate |
| Suspended timber (lift boards) | €30–€60 / m² | Moderate |
| Insulate over solid floor | €40–€80 / m² | High |
| Dig out and re-lay solid floor | Highest | Very high |
These are contractor estimates — get three written quotes and confirm exactly how ventilation and floor levels will be handled.
How the SEAI grant works
Unlike cavity, wall, and attic insulation, floor insulation is not offered as a stand-alone individual SEAI grant. It is supported only through the One Stop Shop (managed retrofit) route:
| Measure | Grant |
|---|---|
| Floor insulation (One Stop Shop only) | €3,500 |
In practice this means you access the floor grant as part of a bundle of measures delivered and project-managed by a registered One Stop Shop, rather than by hiring a contractor and claiming a grant yourself. If you are weighing the managed route against doing measures one at a time, read our guide to One Stop Shop vs individual grants, and see the insulation grants guide for how the schemes fit together.
Where floor insulation fits in your plan
Given the cost and disruption, most homeowners tackle the attic and walls first, then add floor insulation if they are already opening up floors or pursuing a deep retrofit toward a B rating. Timing it with other works keeps the cost and mess to a minimum.
Thinking about a managed retrofit? Check your SEAI grant eligibility or explore all our insulation guides.