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

instrument mechanism / verified-clean

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

The inspectable method record for Insulation/HVAC BTU Load Estimator (Rule of Thumb), kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

NEEDS_REVIEW because the exact climate-factor table, all modifier values and formulas, occupant input handling, area units, and suggested-unit-size mapping are unspecified. The four vectors use an explicitly illustrative convention only: base factors of 20/25/30 BTU/hr/sq ft, supplied multiplicative modifiers, and ceiling modifier equal to ceiling_height_ft/8. This convention is not established by the instrument specification and must not be treated as a validated HVAC method.

- The formula is only a schematic: no actual climate-zone base-factor table is supplied, so the calculation is not reproducible or verifiable.

- Insulation, sun-exposure, ceiling-height, and occupant modifier values and combination rules are unspecified.

- The inputs list omits occupants even though occupants are named as a modifier.

- No formula or sizing rule is supplied for the claimed suggested unit size range.

- A single 20-30 BTU/sq ft baseline is not universally valid for heating and cooling, and heating and cooling loads normally require separate calculations.

## Units and conventions

- BTU requirement means BTU/hr, although the formula should label the output explicitly as BTU/hr.

- Room area is assumed to be in square feet when multiplied by BTU/sq ft.

- The illustrative vectors use ceiling height in feet and a normalized 8-foot reference height.

- The illustrative vectors use multiplicative insulation, sun, ceiling, and occupant modifiers.

- For the metric conversion vector, 1 m² = 10.7639 sq ft.

- The supplied rule-of-thumb factors are treated as heuristic values, not code-compliant or Manual J results.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "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."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

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.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/insulation-hvac-btu-load-estimator-rule-of-thumb/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/insulation-hvac-btu-load-estimator-rule-of-thumb/implementation/>)[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`

- `BOUNDARY_HAZARD_CATALOG.json`