Methodology and Standards

Standards referenced

Standard	Used for
ASHRAE Fundamentals 2021	Load calculations, psychrometric properties, heat transfer
ASHRAE 90.1-2022	Building envelope and equipment efficiency requirements
ASHRAE 62.1-2022	Ventilation requirements (Multi-Zone equation, Ev correction)
ASHRAE 15-2022	Refrigerant safety classifications and ventilation
SMACNA HVAC Duct Construction Standards 2006	Duct sizing, fitting equivalent lengths
IMC (International Mechanical Code)	Code-required ventilation rates, exhaust
IFGC 2021	Fuel gas piping and combustion air
NFPA 90A / 90B / 96 / 99	Air-handling installation, restaurant exhaust, healthcare facilities
NEC 430	Motor circuits — FLA, MCA, MOCP

Calculation methods

Cooling and heating loads

AIM Works supports three calculation methods, selectable per project:

• Simplified (peak design block load)
• CLTD/CLF (Cooling Load Temperature Difference / Cooling Load Factor)
• RTS (Radiant Time Series, per ASHRAE Fundamentals)

Ventilation

ASHRAE 62.1-2022 Multi-Zone equation. Vbz = Rp × Pz + Ra × Az per zone; Voz = Vbz / Ez. System-level Vot computed using the multi-zone Ev correction factor.

Hydronic pipe sizing

Darcy-Weisbach equation with Colebrook-White friction factor. Velocity, head loss, and pump head computed for each segment. Four network topologies supported: Direct Return, Reverse Return (Tichelman), Primary/Secondary, and Ring Main (Hardy-Cross).

Duct sizing

Equal friction method. SMACNA-tabulated equivalent lengths for fittings.

Psychrometrics

Magnus formula for water-vapor saturation pressure; Sprung's wet-bulb approximation; altitude-corrected atmospheric pressure. Full sea-level and altitude-corrected calculations following ASHRAE Fundamentals.

Equipment selection

Block-load capacity matching with engineering safety factors. Chiller, boiler, and DX equipment efficiencies meet or exceed ASHRAE 90.1-2022 §6.4.1 minimum thresholds. Refrigerant compliance per ASHRAE 15-2022 occupancy classification and quantity limits.

Electrical (motor circuits)

NEC 430 — motor full-load amps, MCA (× 1.25), and MOCP rounded to standard breaker sizes per NEC 430.52.

Why this matters

Every calculation in AIM Works displays the method and standard used inline. Reviewers can verify what's behind every number without opening a separate documentation file. This transparency is a core design principle, not an afterthought.

Outputs are advisory; engineering judgment by the user remains required, and all calculations must be reviewed and stamped by a licensed Professional Engineer before construction.

For deeper questions about methodology, contact support@getaimworks.com.