Source: https://guthlabs.ai/docs/instruments/roof-attic-insulation-r-value-calculator/implementation/

instrument implementation / implementation-contract

# Roof/Attic Insulation R-Value Calculator implementation

A source-bound implementation contract for Roof/Attic Insulation R-Value Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## 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**: t7-082

**Effect**: Computation or source lookup only

## Input and validation requirements

An extreme but numerically representable thickness causes the layer multiplication to overflow ordinary floating-point arithmetic. An implementation that accepts it without range validation can return Infinity or a non-finite gap instead of rejecting the input.

## 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": "fiberglass batt",
        "thickness": 9.375,
        "thickness_unit": "in"
      }
    ],
    "climate_zone": 1
  },
  "expected_outputs": {
    "total_R_value_h_ft2_F_per_Btu": 30,
    "recommended_R_value_h_ft2_F_per_Btu": 30,
    "gap_h_ft2_F_per_Btu": 0
  },
  "reference_data": {
    "material_rows": [
      {
        "material": "fiberglass batt",
        "R_per_in": 3.2,
        "source_convention": "widely tabulated standard value"
      }
    ],
    "climate_zone_row": {
      "climate_zone": 1,
      "recommended_attic_R": 30,
      "source_convention": "DOE/ENERGY STAR attic insulation target convention, 2023 guidance"
    }
  },
  "working": "Fiberglass contribution = 9.375 in × 3.2 R/in = 30.0 R. Total R = 30.0 R. Gap = total − target = 30.0 − 30.0 = 0.0 R."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/roof-attic-insulation-r-value-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/roof-attic-insulation-r-value-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/roof-attic-insulation-r-value-calculator/qualification/>)

## Sources and evidence

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

- `VERIFIED_LEDGER.json`

- `evidence-tranche7/tranche7-results.json`