How many rolls of loft insulation do you need? Calculate by loft area and desired depth — and see your estimated annual energy saving.
Enter your loft dimensions to calculate rolls needed and estimate your annual saving.
Mineral wool loft insulation — the UK standard for DIY installation. Available in 100mm rolls for between-joist layer and 170mm rolls for the cross-layer.
View Loft Insulation →Loft insulation is laid in two layers: first between the joists (typically 100mm), then a second cross-layer at 90° over the joists to eliminate thermal bridging through the timber. The current Building Regulations standard is 270mm total — 100mm between joists + 170mm across. Each layer requires approximately one roll per 8 m² of loft area.
The annual energy saving is estimated at £1–£2 per m² of loft area per 100mm of insulation depth. A typical 48 m² semi-detached loft with full 270mm insulation saves approximately £150–£200 per year compared to no insulation.