HVAC Load Calculation & Equipment Sizing Assistant
Calculate HVAC loads, size equipment, and validate specifications against code
What You Can Do
You can accelerate HVAC design workflows by inputting building parameters—envelope characteristics, occupancy data, climate conditions, and existing systems—and receiving calculated heating/cooling loads, equipment sizing recommendations, and zone-by-zone analysis. Claude organizes complex building data into actionable design parameters and specification summaries for client review, permit submission, and professional validation against ASHRAE and ACCA standards.
Features
Processes building envelope (insulation, window performance, air leakage), occupancy schedules, and climate data to estimate sensible and latent heating/cooling loads by zone
Cross-checks proposed equipment (air handlers, furnaces, heat pumps) against calculated loads to flag oversized or undersized selections and recommend right-sized alternatives
Calculates duct dimensions, airflow rates, and pressure drops to support balanced system design and code compliance
Organizes multi-zone systems with room-level load summaries, diversity factors, and equipment distribution recommendations
Creates formatted design documents including load tables, equipment schedules, and design notes ready for client review or permit submission
Provides structured templates to gather missing building information (construction type, occupancy hours, internal gains, existing equipment specs)
Flags calculations against ASHRAE 62.1 (ventilation), ASHRAE 90.1 (efficiency), and local energy code requirements for validation
Documents preliminary vs. detailed load estimates and equipment selection alternatives with rationale for design decisions
Example Output
Example 1: Commercial Office Load Summary
Building: 10,000 sq ft, 2-story office, Denver, CO
Zone A (Perimeter South): 125 kBtu/h cooling, 95 kBtu/h heating → Size 4-ton unit
Zone B (Core): 85 kBtu/h cooling, 60 kBtu/h heating → Size 3-ton unit
Total System: 210 kBtu/h cooling | 155 kBtu/h heating
Recommended Equipment: Two 5-ton rooftop units (6% design margin)
Duct: 2,400 CFM @ 0.15" w.g. friction loss (8×10" supply main)
- ⚠️ Alert: Original spec of 7.5-ton single unit = 25% oversizing → Reheat penalty
Example 2: Residential Heat Pump Sizing
House: 3,200 sq ft, 1970s construction, Minneapolis, MN
Heating Load: 38,000 BTU/h @ -13°F design
Cooling Load: 24,500 BTU/h @ 95°F outdoor
Recommended: 4-ton cold-climate heat pump + 10 kW backup resistance
Zoning: 2 zones (upper/lower) → 2 × 2-ton cassettes or ducted split
Ventilation: 90 CFM continuous mechanical (ASHRAE 62.2)
✓ Verified against MN Energy Code; equipment eligible for rebates
What's Included
- SKILL.md: System instruction file with load calculation methodology, code-reference standards, and validation frameworks
- Building Data Intake Template: Structured questionnaire capturing envelope specs, occupancy patterns, climate zone, existing systems, and design constraints
- Load Calculation Worksheet: Room-by-room or zone summary table with sensible load, latent load, and design heating/cooling totals
- Equipment Sizing Checklist: Cross-reference table for matching calculated loads to manufacturer equipment (tonnage, CFM, SEER/AFUE ratings)
- Specification Summary Template: Client-ready design document format including load tables, equipment schedule, ductwork summary, and code compliance notes
- Code Compliance Reference: Quick-check matrix for ASHRAE 62.1, 90.1, and common local energy code requirements
Who It's For
- HVAC Design Engineers — Accelerate preliminary load calculations and equipment selections for new construction and major renovations
- Mechanical Contractors — Validate customer equipment selections and identify oversizing/undersizing before bid submission
- Energy Auditors — Support retrofit analysis by calculating existing building loads and sizing replacement equipment
- Facility Managers — Assess equipment adequacy for building additions or occupancy changes
- Architects & Building Designers — Generate MEP design data for permitting and cost estimation
Best For
- Commercial office and retail building HVAC design
- Residential single-family and light multifamily heat pump/furnace sizing
- Zone-by-zone analysis for buildings with distinct thermal conditions (perimeter vs. core, upper vs. lower floors)
- Equipment validation when reviewing contractor proposals or existing system performance
- Multi-unit housing load calculations and equipment schedules
- Retrofit and renovation HVAC specification updates
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