Composite Wall R-value / U-value Calculator implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t4-132

Effect

Computation or source lookup only

Input and validation requirements

A zero thermal-conductivity input causes division by zero in L/k, producing undefined R-value, U-value, and heat flow. The instrument must reject k=0 rather than propagate a numeric result.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "layers": [
      {
        "material": "brick",
        "thickness": 0.1,
        "thickness_unit": "m",
        "k": 0.5,
        "k_unit": "W/(m·K)"
      },
      {
        "material": "mineral wool insulation",
        "thickness": 0.1,
        "thickness_unit": "m",
        "k": 0.04,
        "k_unit": "W/(m·K)"
      },
      {
        "material": "gypsum board",
        "thickness": 0.012,
        "thickness_unit": "m",
        "k": 0.12,
        "k_unit": "W/(m·K)"
      }
    ],
    "film_resistances": {
      "inside": 0.13,
      "outside": 0.04,
      "unit": "m²·K/W"
    },
    "area": 40,
    "area_unit": "m²",
    "delta_T": 25,
    "delta_T_unit": "K"
  },
  "expected_outputs": {
    "Rtotal": 2.97,
    "Rtotal_unit": "m²·K/W",
    "U": 0.3367003367,
    "U_unit": "W/(m²·K)",
    "q": 336.7003367,
    "q_unit": "W"
  },
  "working": "Brick: L/k = 0.1/0.5 = 0.2 m²·K/W. Insulation: 0.1/0.04 = 2.5 m²·K/W. Gypsum: 0.012/0.12 = 0.1 m²·K/W. Films: 0.13 + 0.04 = 0.17 m²·K/W. Rtotal = 0.2 + 2.5 + 0.1 + 0.17 = 2.97 m²·K/W. U = 1/2.97 = 0.3367003367 W/(m²·K). q = U·A·ΔT = 0.3367003367·40·25 = 0.3367003367·1000 = 336.7003367 W."
}

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche4/tranche4-results.json