Insulation Calculator
Calculate how many insulation batts you need for any wall, ceiling or underfloor area. Includes R-value guide for different climate zones. Works for glasswool, rockwool and polyester batts.
🔨 Insulation Calculator
📐 How It Works
Insulation batts are sized to fit snugly between studs or joists. Standard 450mm batt width fits 450mm stud spacing. Total area divided by individual batt area gives the count, plus 10% waste for cuts around obstacles.
📋 Worked Example
Ceiling 12m × 10m = 120 m². Standard 1160×580mm batts at 600mm spacing: Batt area = 0.673 m². Batts = 120 × 1.10 ÷ 0.673 = 196 batts.
❓ Frequently Asked Questions
Australia NCC minimum R-values vary by climate zone and element: Zone 1-2 (tropical): ceiling R2.0, wall R1.5. Zone 3-4 (temperate): ceiling R3.5, wall R2.0. Zone 5-6 (cool): ceiling R4.1, wall R2.8. Zone 7 (cold): ceiling R5.1, wall R3.8. Check the NCC for your specific zone and building type.
Glasswool batts are the most common — good performance, low cost, itchy to handle (wear PPE). Polyester batts are non-itchy, easier to handle and suitable for allergy-sensitive environments but cost more. Rockwool (mineral wool) has better fire and acoustic performance for party walls. All achieve similar R-values at similar thickness.
Lay batts between ceiling joists with the foil face (if present) facing down toward the living space. Butt batts tightly together with no gaps — gaps dramatically reduce effectiveness. Don't compress batts — they insulate through trapped air. Cover the top with sarking or reflective foil if specified.
Yes — topping up existing ceiling insulation is one of the most cost-effective home energy improvements. Lay new batts perpendicular to existing batts to cover gaps and add R-value. Ensure existing batts are not wet or damaged before adding new material.