Duct Wrap / Liner Material Takeoff
External duct-wrap insulation area and rolls, where the overlap and corner compression add to the bare surface.
Example
You enter
- Duct width (in) 20
- Duct height (in) 12
- Run length (ft) 40
- Overlap + waste multiplier 1.15
- Installed coverage per roll (ft²) 100
You get
- Perimeter (ft) 5.333
- Wrap (ft²) 245.33
- Wrap rolls to order 3
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
Scopeperimeter = 2 x (width + height); wrap = perimeter x length x overlap/waste factor; rolls = ceil(wrap / roll coverage). A 20 x 12 in duct, 40 ft long, needs 245 sf of wrap (3 rolls of 100 sf); a larger 30 x 20 in duct needs 383 sf (4 rolls) - the perimeter, not the length, drives the wrap. The factor (~1.15) covers the taped overlap; internal liner is taken off on the interior perimeter.
Formula or tableperimeter_ft = 2 x (width_in + height_in) / 12; wrap_sf = perimeter_ft x length_ft x overlap_waste_factor; rolls = ceil(wrap_sf / roll_coverage_sf).
Source and editionDuct-wrap takeoff identity by name (developed area x overlap/waste factor; rolls from wrap / coverage); first-principles takeoff arithmetic.
Free accessThe developed-area geometry is public first-principles; the product's installed coverage comes from the manufacturer.
What governsEstimate. AHJ and licensed professional govern.
API field nameswidth_in, height_in, length_ft, overlap_waste_factor, roll_coverage_sf, perimeter_ft, wrap_sf, rolls
- Overlap/waste factor ~1.15 for the taped 2 in overlap and corner compressioninsulation practice
- Roll coverage the product's installed coverage per roll (less than nominal), from the manufacturerwrap manufacturer