Insulation Calculator

Loft roll, PIR board, mineral wool, insulated plasterboard, loose fill, and pipe lagging

Insulation Type

Waste Allowance (%)

10%

10% is typical; increase to 15-20% for awkward shapes or many joists/rafters to work around.

Cost per roll / board / bag

Labour per m²

Delivery (flat fee)

Units to Buy
-
rolls / boards

Total Net Area

m²

Inc. Waste

m²

Type	Best for
Loft Roll	Loft floors, between joists, sloped roofs
PIR Board	Floors, flat roofs, internal walls, cold bridges
Mineral Wool Slab	Stud frames, rafter spaces, acoustic walls
Insulated PB	Internal wall dry-lining (plasterboard + PIR)
Loose Fill	Loft top-up, cavity wall injection
Pipe Lagging	Hot/cold pipes, cylinders, tanks

Minimum recommended loft depth is 270 mm of mineral wool. Always check Part L of Building Regulations for the latest requirements.

Standard sections are sold in 1 m lengths.
A 22 mm bore × 13 mm wall section fits a standard 22 mm copper pipe.
Minimum lagging thickness for frost protection is 13 mm; exposed or unheated areas need 25 mm.
Foam lagging is typically sold in packs of 10 × 1 m sections.
Allow 10% extra for bends, joints and valves.