wattlab-assumptions

name

wattlab-assumptions

description

Use when building sparse / minimal-info EnergyPlus twins: defaults hierarchy, Ideal Loads vs explicit HVAC, PNNL infiltration/OA candidates, assumption ledger, TMY→AMY ladder, and short/long fuel G14 dial (WWR/glass/ACH then banded SAT/reheat). Triggers on: sparse building, minimal info, defaults, IdealLoads, assumption ledger, autosize, constrain plant, TMY, AMY, prototype, short gas, CVRMSE, calibrate dial, WWR, infiltration.

WattLab assumptions — agent is the assumption-maker

EnergyPlus simulates; you choose, justify, and log defaults. EnergyPlus-MCP inspects/patches/sims — it does not pick TMY vs AMY or invent city/area.

Full ladder: ../../docs/SPARSE_BUILDING_PLAYBOOK.md. Fuel dial depth: ../wattlab-twin-calibrate-dial/SKILL.md · ../../docs/TWIN_DIAL_PLAYBOOK.md.

Hierarchy (strict order)

1. Human / FM facts — building_type, city, floor_area_ft2, lat/lon, nameplate tons/hp, known schedules. NEEDS_INPUT if missing. Never invent.
2. Evidence — vibe19 dump (schedules, setpoints, FDD, weather_observed), campus bills, buildings.json.
3. Seed model — nearest archetype IDF (today: 5ZoneAirCooled screening) or human custom_idf / future DOE–PNNL prototype by type/size/code/climate.
4. Code / climate catalog — WattLab defaults (archetypes, climate.json, codes). Unknown city keeps user label + honest substitute EPW note (no silent Madison remap).
5. Literature defaults (stamp source) — ASHRAE-style schedules; OA methods; PNNL infiltration candidate when no measured leakage.

Partition like a good conceptual modeler

Stage	Focus
Project	Site, area, climate, bills window, rates
Design	Simple shell / prototype; perimeter-core OK for screening
Schedules	Occupancy / lighting / equipment / HVAC avail
Baseline	LPD, EPD, people density, ventilation, infil, setpoints
Measures	One hypothesis per runs/<id>/
Results	Monthly vs bills, unmet hours, area scale, weather mode, peak kW, G14

After TMY screening: wattlab calibrate-campaign (bill months → AMY → G14) — ../../docs/CALIBRATE_AND_DELIVERABLES.md.

Hard-size nameplate: scale by 1/prototype_area_scale when scale > 1.5; refuse outside [0.25, 4.0]. City troy → detroit catalog (user label preserved).

Ideal Loads vs explicit system

• Quick model, not all details known → Ideal Loads + rigorous envelope / schedule assumptions first (when IDF path supports it).
• Compare HVAC pathways / plant ECMs → explicit seed (5Zone VAV today); always show prototype_area_scale vs target ft².
• Keep scenarios separate: (A) autosized conceptual, (B) constrained to nameplate, (C) outage/recovery. Never merge into one “truth” run.

Assumption ledger (publish every campaign)

For each key: value, source (user / dump / default / literature), confidence (high/med/low), sensitivity note.

Minimum keys: occupancy density, LPD, EPD, OA rate method, infiltration, thermostat / fan hours, WWR, HVAC family, weather mode (TYPICAL_YEAR_SCREENING / ACTUAL_YEAR_CALIBRATION / SUBSTITUTE_CLIMATE_CONCEPTUAL_ONLY), prototype_area_scale.

For ECM-OCC-STANDBY-DCV, record the verified occupied and standby schedules, minimum-ventilation constraint, sensor calibration evidence, and the source of the DCV airflow reduction. Never infer zero occupied OA from a screening proxy.

Short / long fuel playbook (Twin G14 dial)

Autosized plant is fine for sparse twins — dial envelope + loads + as-operated SAT/VAV, not invented nameplate tons. Full playbook: ../../docs/TWIN_DIAL_PLAYBOOK.md (Cursor skill: wattlab-twin-calibrate-dial). Tools publish chain: ../../docs/AGENT_TOOLS.md.

Gas short annually (model ≪ bills)

1. Lock good geometry (e.g. stacked Floor_1…Floor_N — not DOE mid×4 when the human wants floor massing).
2. Raise WWR toward site (curtain wall often 0.70–0.75).
3. Leaky glass: U ≈ 0.80–1.0 IP, not pretty DOE U.
4. Infiltration ACH ladder; stop near annual gas ±5%.
5. Only then HVAC shape (below).

Elec short annually

• Raise LPD / EPD (W/m²) before plant oversizing.

Annual flat but monthly gas CVRMSE fails (winter high / summer low)

1. Read vibe19 AHU discharge-air-temp / SP by month (fan-on).
2. Summer dump (often ~50°F when dump shows it) + higher VAV min-flow in true summer only.
3. Warmer winter SAT + shorter winter OA; band months — do not hold cold dump across long shoulder seasons (blows Oct/Aug gas).
4. If bills ≠ HDD (Feb peak / Oct tiny), band aggressively and document residual CV.

G14 pass = both fuels |NMBE|≤5% and CVRMSE≤15%. Annual % alone ≠ calibrated. Always write calibration_scorecard.json in the Twin-expected nested shape.

Do not

• Invent office / Madison / Chicago for a real dump.
• Claim G14 on TMY vs non-overlapping bills or unscaled ~10k ft² prototype.
• Quietly publish ROI when guardrails hit INVESTIGATE.
• Call stacked-twin calibrate “done” on DOE mid×4 zoning when the user expects Floor_1–N.
• Start gas-short campaigns with plant oversizing before envelope / infil.