Rigid / Continuous Insulation Board Count
Rigid continuous-insulation boards (XPS, polyiso, EPS) for an area, with waste and layers.
Example
You enter
- Area to insulate (ft²) 1600
- Board area (ft²) 32
- Number of layers 2
- Waste allowance (%) 8
You get
- Boards 108
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
Scopeboards = ceil(area x (1 + waste/100) / board area) x layers. A 1,600 sf wall in 4 x 8 boards at 8% waste is 54 boards a layer, so a two-layer continuous-insulation assembly with offset seams is 108 boards; a single layer is 54. The layer count, set by the required continuous-insulation R, is the multiplier; fasteners, plates, and tape are taken off separately. Distinct from spray-foam board feet and batt coverage.
Formula or tableboards = ceil(area_sf x (1 + waste_pct/100) / board_area_sf) x layers.
Source and editionRigid-insulation board-count identity by name (boards per layer from area over board area with waste, times the layers); first-principles arithmetic.
Free accessThe board-count arithmetic is public first-principles; the continuous-insulation R and layers come from the energy code.
What governsEstimate. AHJ and licensed professional govern.
API field namesarea_sf, board_area_sf, layers, waste_pct, boards
- Board area ~32 sf for a 4 x 8 board (default); the product size governsinsulation manufacturer
- Layers set by the required continuous-insulation R with offset seamsIECC / energy code