Radiant barrier calculator
Area, roll size and overlap: you get rolls of radiant barrier, foil tape for the seams and staples.
Purchase quantity
861.113 ft²
Net measurement: 861.113 ft² · Waste 10 %
- Radiant barrier rolls4 roll
- Usable area per roll309.462 ft²
- Foil tape (50 m roll)2 roll
- Staples (8 per m²)1 box
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How it's calculated (visible formula)
usable per roll = (width − overlap) × length; rolls = ceil(area × (1 + waste) ÷ usable); tape = seam length
- Net geometric measurement, no waste.
- Adjustable waste % for cuts and breakage.
- Purchase rounded up to sellable units (boxes, bags, buckets, boards).
How to calculate it, step by step
- Measure the area (under the roof deck or on the attic floor).
- Enter roll width, length and overlap.
- Work out usable area per roll.
- Work out rolls with waste.
- Add foil tape for seams and staples.
Worked example: 860 sq ft with 4 × 82 ft rolls, 2 in overlap
- Usable ≈ 28.75 m² (310 sq ft)
- ≈ 947 sq ft ÷ 310 = 3.1
→ 4 rolls, 2 rolls of tape and 1 box of staples.
Common mistakes
- No air gap — it won't reflect.
- Laying it directly on insulation (loses effect).
- Letting dust cover it on attic floors.
Pro tips
- Always leave an air space facing the shiny side.
- Staple to rafters with the reflective face toward the air space.
- Tape seams with foil tape for continuity.
- Best in hot, sunny climates.
From calculation to quote
Add labour, overhead and your margin, and generate the professional PDF.
FAQs
- Does it need an air gap?
- Yes, at least ¾ in facing the shiny side.
- Does it replace insulation?
- No — it cuts radiant heat gain in summer on top of insulation.
- Where does it go?
- Stapled to the underside of rafters, shiny side facing the air space.
- How much does it cool the attic?
- It can drop attic temperatures noticeably in summer if well installed.
- Does it help in winter?
- A little; its main effect is blocking summer radiant heat.
- Shiny side up or down?
- Toward the air space — usually down when stapled to rafters.
Sources and standards
Maintained by Srikanta M · Formula v1.0.0 · Verified 2026-09-10 · Updated 2026-09-10 · Limits: quantity estimation, not structural design or site supervision.