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Attic Square · 1.000 ft²
Set the tool size, pick the product on the bag and the rated R-value. You get the minimum sample weight in grams — weigh your cut sample to that line.
Pass if sample ≥
—g
area 1.000 ft² min — lb/ft² depth — ≈ — lb/ft³
—

Reading a different bag?

Coverage minimums move by product & edition. Type the bag chart's min lb/ft² for your R-value:

× 453.6 = 252 g

Title 24 RA3.5 — how to sample

Attics: take the sample where it looks thinnest (ICAA TB #17/#33 method); record weight-per-ft² on the CF3R.
≥ 6 locations per surface type (wall, roof/ceiling, floor). Walls add a low and a high spot.
Weight beats depth: settling changes thickness, not mass — the gram pass-line holds before or after settling. Still confirm minimum depth too.
Stay clear of blow points — sample ≥ 2 ft from any fill hole; don't pack fill into the frame.
Always confirm against the bag label on site. Figures are published manufacturer examples (ASTM C1374) and vary by product, edition and blowing machine. Older editions are flagged ⚠. For permits dated on/after 1 Jan 2026 this is the ECC program (CF3R · Certificate of Verification).
ecctools.org — field compliance tools.