Source: https://guthlabs.ai/docs/instruments/insulation-hvac-btu-load-estimator-rule-of-thumb/implementation/

instrument implementation / implementation-contract

# Insulation/HVAC BTU Load Estimator (Rule of Thumb) implementation

A source-bound implementation contract for Insulation/HVAC BTU Load Estimator (Rule of Thumb); 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**: t5-111

**Effect**: Computation or source lookup only

## Input and validation requirements

The estimator overflows to Infinity for an extreme but numerically representable area, and its result is convention-sensitive because the specification does not define whether sun exposure raises cooling load or lowers heating load, whether ceiling height is in feet or metres, or how BTU/hr maps to a suggested unit-size range.

## 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": {
    "area_sq_ft": 400,
    "climate_zone": "mild",
    "base_factor_btu_per_sq_ft": 20,
    "insulation_modifier": 0.9,
    "sun_exposure_modifier": 0.9,
    "ceiling_height_ft": 8,
    "ceiling_reference_ft": 8,
    "ceiling_modifier": 1,
    "occupants": 2,
    "occupant_modifier": 1
  },
  "expected_outputs": {
    "estimated_btu_per_hr": 6480,
    "suggested_unit_size_range": null
  },
  "working": "400 sq ft × 20 BTU/hr/sq ft = 8,000 BTU/hr; 8,000 × 0.9 insulation = 7,200; 7,200 × 0.9 sun exposure = 6,480; 6,480 × 1 ceiling modifier × 1 occupant modifier = 6,480 BTU/hr. Suggested unit range cannot be computed because no sizing-range rule is supplied."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/insulation-hvac-btu-load-estimator-rule-of-thumb/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/insulation-hvac-btu-load-estimator-rule-of-thumb/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/insulation-hvac-btu-load-estimator-rule-of-thumb/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-tranche5/tranche5-results.json`