{
  "schemaVersion": 1,
  "slug": "insulation-r-value-calculator",
  "category": "construction",
  "kind": "implementation",
  "independentValidation": false,
  "implementationHash": "ec4fe2865097ff9d575a684d18238d61150004d9335ec69e4f04efbcfc58020c",
  "provenance": "Generated from the calculation contract used by the published page. Publication is not external validation.",
  "sourceFiles": [
    "data/calculators/insulation-r-value-calculator.json",
    "src/engine.js"
  ],
  "runtimeSource": "/sources/engine.txt",
  "runtimeHash": "5c888d8898afbdee36267bb9977829e1e2ac568f6677c8ee87469c139864645c",
  "scope": "The compute function records implemented equations, constants, lookup tables and custom rules. Inputs record defaults and allowed values; outputs record precision and units. Defaults are examples, not recommendations. General background references are not evidence for this specific algorithm.",
  "publishedFormula": {
    "formula": "R = t ÷ (6.9336 × k) × n + 0.85",
    "vars": [
      [
        "R",
        "Total R-value (imperial)"
      ],
      [
        "t",
        "Layer thickness (in)"
      ],
      [
        "k",
        "Thermal conductivity (W/m·K)"
      ],
      [
        "n",
        "Number of identical layers"
      ],
      [
        "RSI",
        "Metric R-value (m²·K/W)"
      ]
    ],
    "note": "Air films add 0.85 R (0.15 RSI) when enabled; metric RSI = t × 0.0254 ÷ k per layer; U-factor = 1 ÷ R."
  },
  "externalEvidence": {
    "reviewedAt": "2026-10-12",
    "sources": [
      {
        "name": "US Department of Energy — Insulation and R-value",
        "url": "https://www.energy.gov/sites/prod/files/guide_to_home_insulation.pdf"
      }
    ],
    "referenceRole": "definition",
    "implementationHash": "ec4fe2865097ff9d575a684d18238d61150004d9335ec69e4f04efbcfc58020c",
    "basis": "R = t ÷ (6.9336 × k) × n + 0.85",
    "limitations": "The references explain definitions and methods; any extra preset must be checked against the assumptions on this page."
  },
  "contract": {
    "compute": "const rPerLayer = thickness/(6.9336*(conductivity || 0.04)); const totalR = rPerLayer*layers+(includeAirFilms === 'yes' ? 0.85 : 0); const rsiPerLayer = (thickness*0.0254)/(conductivity || 0.04); const totalRsi = rsiPerLayer*layers+(includeAirFilms === 'yes' ? 0.15 : 0); return { rValue: totalR, rsi: totalRsi, uFactor: totalR > 0 ? 1/totalR : 0, thicknessMm: thickness*25.4*layers };",
    "inputs": [
      {
        "name": "thickness",
        "type": "number",
        "default": 3.5,
        "min": 0.1,
        "max": 36,
        "step": 0.1,
        "slider": true
      },
      {
        "name": "conductivity",
        "type": "number",
        "default": 0.04,
        "min": 0.005,
        "max": 5,
        "step": 0.005,
        "slider": true
      },
      {
        "name": "layers",
        "type": "number",
        "default": 1,
        "min": 1,
        "max": 20,
        "step": 1,
        "slider": true
      },
      {
        "name": "includeAirFilms",
        "type": "select",
        "default": "yes",
        "options": [
          {
            "value": "yes"
          },
          {
            "value": "no"
          }
        ]
      }
    ],
    "outputs": [
      {
        "name": "rValue",
        "precision": 2,
        "unit": "R"
      },
      {
        "name": "rsi",
        "precision": 3,
        "unit": "m²K/W"
      },
      {
        "name": "uFactor",
        "precision": 4,
        "unit": "Btu/h·ft²·°F"
      },
      {
        "name": "thicknessMm",
        "precision": 1,
        "unit": "mm"
      }
    ],
    "interpret": null
  }
}