The attic is where most heat escapes in a typical house, which also makes it where insulation pays back fastest.
For a 60 m² attic at 300 mm thick you'll need about 18 m³ of insulation – depending on pack size that's typically 12–14 packs. Add 5 % waste on top.
Volume = area × thickness. 60 m² × 0.3 m = 18 m³.
Pack sizes vary, but a typical pack covers 4–5 m² at 195 mm. For 300 mm you'll use about 1.5 packs for the same area.
Add 5 % waste for trims around rafters, penetrations and edges.
60 m² attic at 300 mm: if a pack covers 5 m² at 195 mm, then 300 mm equates to 5 × (195/300) = 3.25 m² per pack. 60 ÷ 3.25 = 18.5 → 19 packs. Add 5 % waste and you're at 20 packs.
Enter your attic area and insulation thickness – the calculator works out packs including recommended waste.
Building regs typically want 300+ mm for new builds. Retrofits can often be less – check the current rules for your project.
Both have almost the same insulation value. Rock wool is slightly more fire-resistant and moisture-tolerant; glass wool is often cheaper.
Yes, on the warm side (room side). Without a vapour barrier, moisture rises into the insulation and you get mould.
A well-insulated attic typically saves a meaningful chunk on heating, depending on house size and heat source.
Keep going with one of these – they pair well with what you just read.
Insulate walls and ceilings
Materials, thickness, vapor barriers and the mistakes that make insulation useless.
Read guide →Build a drywall partition wall
Stud spacing, sheets, screws and the usual pitfalls. A clean DIY partition wall.
Read guide →Deck project from start to finish
Step-by-step guide to planning and building a deck. Measuring, materials, budget and mistakes.
Read guide →Drywall calculator
Calculate the number of drywall sheets or panels for walls or ceilings.
Open calculator →Paint calculator
Calculate litres of paint for walls and ceilings based on area and coverage.
Open calculator →Flooring calculator
Calculate packs of laminate or floorboards based on area and waste.
Open calculator →Create a free account and explore all features with a complete demo project.
No credit card required. Free demo project included.