{
  "id": "spray-foam",
  "version": "d1469cbfbfed",
  "status": "published",
  "name": "Spray Foam Calculator",
  "question": "How much spray foam do I need?",
  "summary": "Computes the board feet of spray foam insulation for an area and thickness, with extra for waste, how many kits to buy, and the R-value of open-cell or closed-cell foam.",
  "category": "construction",
  "subcategory": "materials",
  "url": "https://www.acalculator.org/construction/spray-foam-calculator",
  "markdown": "https://www.acalculator.org/construction/spray-foam-calculator.md",
  "kind": "function",
  "method": "Board feet = area (ft²) × thickness (in); to buy = board feet × (1 + extra ÷ 100); kits = to buy ÷ kit yield, rounded up; R-value = R per inch × thickness (in).",
  "assumptions": [
    "A board foot of foam is 1 ft² sprayed 1 in thick (144 in³).",
    "Closed-cell foam is R-6.3 per inch and open-cell R-3.7 per inch, from DOE’s Building America figures (3 in closed-cell is R-19, 7.5 in open-cell R-28); your product’s label may differ.",
    "The extra for waste covers overspray and uneven thickness; 10% by default."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "a": {
        "title": "Area to cover",
        "description": "The wall, roof or floor area to spray, openings left out.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "area",
        "exclusiveMinimum": 0,
        "maximum": 1000000
      },
      "t": {
        "title": "Thickness",
        "description": "How thick the foam is sprayed.",
        "type": [
          "number",
          "string"
        ],
        "x-quantity": "length",
        "exclusiveMinimum": 0,
        "maximum": 1
      },
      "foam": {
        "title": "Foam type",
        "description": "Open-cell (about R-3.7 per inch), closed-cell (about R-6.3 per inch), or your product’s own R per inch.",
        "type": "string",
        "enum": [
          "closed",
          "open",
          "custom"
        ]
      },
      "r": {
        "title": "R-value per inch",
        "description": "The R-value per inch on your foam’s label or data sheet.",
        "type": "number",
        "exclusiveMinimum": 0,
        "maximum": 20
      },
      "extra": {
        "title": "Extra for waste",
        "description": "Foam to add for overspray and uneven thickness.",
        "type": "number",
        "x-unit": "percent",
        "minimum": 0,
        "maximum": 100
      },
      "kit": {
        "title": "Kit yield (board feet)",
        "description": "The board feet one kit or set covers, from its label: for example 200 or 600.",
        "type": "number",
        "minimum": 1,
        "maximum": 1000000
      }
    }
  },
  "outputs": {
    "boardFeet": {
      "label": "Board feet to buy",
      "description": "Area (ft²) × thickness (in) × (1 + extra ÷ 100).",
      "format": "number"
    },
    "netBoardFeet": {
      "label": "Board feet sprayed",
      "description": "Area (ft²) × thickness (in), no extra.",
      "format": "number"
    },
    "kits": {
      "label": "Kits",
      "description": "Board feet to buy ÷ kit yield, rounded up.",
      "format": "integer"
    },
    "rValue": {
      "label": "R-value",
      "description": "R per inch × thickness in inches.",
      "format": "number"
    },
    "cubicFeet": {
      "label": "Volume (ft³)",
      "description": "Board feet ÷ 12.",
      "format": "number"
    },
    "cubicMeters": {
      "label": "Volume (m³)",
      "description": "The foam volume to buy in cubic meters.",
      "format": "number"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "a": 46.45152,
      "t": 0.0508,
      "foam": "closed",
      "r": 6,
      "extra": 10,
      "kit": 600
    },
    "outputs": {
      "boardFeet": 1100,
      "netBoardFeet": 1000,
      "kits": 2,
      "rValue": 12.6,
      "cubicFeet": 91.66666666666667,
      "cubicMeters": 2.5957109376
    },
    "text": "Buy 1,100 bd ft of spray foam (kits: 2) for about R-12.6."
  },
  "examples": [
    {
      "given": {
        "a": 46.45152,
        "t": 0.0508,
        "foam": "closed",
        "extra": 10,
        "kit": 600
      },
      "expect": {
        "boardFeet": 1100,
        "netBoardFeet": 1000,
        "kits": 2,
        "rValue": 12.6,
        "cubicFeet": 91.66666666666667,
        "cubicMeters": 2.5957109376
      },
      "source": "hand calculation in content.mdx: 500 × 2 = 1,000 board feet × 1.1 = 1,100; 1,100 ÷ 600 = 1.83, so 2 kits; 6.3 × 2 = R-12.6; US DOE Building America Solution Center, Unvented Conditioned Attic with Spray Foam Insulation Below Roof Deck: 3 in of closed-cell spray foam is R-19 and 7.5 in of open-cell spray foam is R-28, https://basc.pnnl.gov/resource-guides/unvented-conditioned-attic-spray-foam-insulation-below-roof-deck (retrieved 2026-10-18); NIST SP 811 (2008), Appendix B: 1 ft = 12 in, 1 in = 2.54 cm exactly"
    },
    {
      "given": {
        "a": 111.483648,
        "t": 0.1397,
        "foam": "open",
        "extra": 0,
        "kit": 600
      },
      "expect": {
        "boardFeet": 6600,
        "kits": 11,
        "rValue": 20.35
      },
      "source": "hand calculation in content.mdx: 1,200 × 5.5 = 6,600 board feet ÷ 600 = 11 kits; 3.7 × 5.5 = R-20.35; US DOE Building America Solution Center, Unvented Conditioned Attic with Spray Foam Insulation Below Roof Deck: 3 in of closed-cell spray foam is R-19 and 7.5 in of open-cell spray foam is R-28, https://basc.pnnl.gov/resource-guides/unvented-conditioned-attic-spray-foam-insulation-below-roof-deck (retrieved 2026-10-18)"
    },
    {
      "given": {
        "a": 20,
        "t": 0.05,
        "foam": "custom",
        "r": 7,
        "extra": 0,
        "kit": 200
      },
      "expect": {
        "boardFeet": 423.7760006578631,
        "kits": 3,
        "rValue": 13.779527559055119,
        "cubicMeters": 1
      },
      "source": "hand calculation in content.mdx: 20 m² = 215.278 ft², 5 cm = 1.9685 in, 215.278 × 1.9685 = 423.78 board feet; 20 × 0.05 = 1 m³; 7 × 1.9685 = R-13.78; NIST SP 811 (2008), Appendix B: 1 ft = 12 in, 1 in = 2.54 cm exactly"
    }
  ],
  "sources": [
    "US Department of Energy, Building America Solution Center (PNNL), Unvented Conditioned Attic with Spray Foam Insulation Below Roof Deck: 3 in of closed-cell spray foam is R-19 and 7.5 in of open-cell spray foam is R-28 (divided by the thickness: R-6.33 and R-3.73 per inch, shown as 6.3 and 3.7). https://basc.pnnl.gov/resource-guides/unvented-conditioned-attic-spray-foam-insulation-below-roof-deck (retrieved 2026-10-18)",
    "NIST SP 811 (2008), Appendix B: 1 ft = 12 in, 1 in = 2.54 cm exactly, so 1 ft² = 0.09290304 m² and 1 ft³ = 0.028316846592 m³. https://www.nist.gov/pml/special-publication-811 (retrieved 2026-10-18)"
  ],
  "related": [
    "insulation",
    "board-foot"
  ],
  "changelog": []
}