Gross floor area of the conditioned space in square feet. Used to calculate lighting and equipment internal loads. Typical: 100-500 ft² per zone, 2000-50000 ft² total for commercial.

Maximum number of occupants expected in the space. Drives people sensible/latent loads and ventilation airflow per ASHRAE 62.1. Typical: 1 per 100-200 ft² office, 1 per 15-20 ft² assembly.

Occupant activity level. Determines sensible and latent heat gain per person from ASHRAE Fundamentals. Office ~250 BTU/hr sensible; restaurant and manufacturing are higher. If omitted, defaults to office.

Installed lighting power density in watts per square foot. ASHRAE 90.1 LPD: 0.82 W/ft² office, 1.06 retail, 0.66 warehouse. Include ballast/driver losses. If omitted, defaults to 1.0 W/ft2.

Plug/process equipment power density in watts per square foot. Typical office: 1.0-2.0; datacenter: 50-150; laboratory: 3-10. Use diversity-adjusted values. If omitted, defaults to 1.5 W/ft2.

Number of exterior walls exposed to outdoor conditions. Affects total wall conduction load. Corner rooms typically have 2; interior rooms have 0. 0 for interior zones, 1-2 for perimeter, 3-4 for corner rooms. If omitted, defaults to 2.

Total gross exterior wall area (opaque + glazing) in square feet. Measure all exterior walls combined, including window openings. Estimate: wall_height × perimeter_length for exposed walls.

Total window/glazing area in square feet across all exterior walls. Must not exceed wall_area_ft2. Drives both conduction and solar heat gain. Typical window-to-wall ratio: 20-40% for offices, 10-20% for industrial.

Overall thermal transmittance of opaque exterior walls in BTU/hr-ft2-F. ASHRAE 90.1 typical: 0.06-0.12 depending on climate zone and construction. If omitted, defaults to 0.08 BTU/hr-ft2-F.

Overall thermal transmittance of windows in BTU/hr-ft2-F. Single pane ~1.0; double low-e ~0.30; triple ~0.20. Per NFRC rating. Typical: 0.25-0.35 for low-e double, 0.50 for standard double, 1.0 for single. If omitted, defaults to 0.50 BTU/hr-ft2-F.

Solar Heat Gain Coefficient of windows, dimensionless 0-1. Lower values reduce solar gain. ASHRAE 90.1 limits range 0.25-0.40 by climate zone. If omitted, defaults to 0.40.

Design outdoor dry-bulb temperature in degrees Fahrenheit. Use ASHRAE 0.4% cooling design temperature for the project location. ASHRAE design conditions: 90-105 F for US summer, check local 0.4% DB. If omitted, defaults to 95 F.

Design indoor dry-bulb temperature setpoint in degrees Fahrenheit. ASHRAE 55 comfort range: 72-78 F for cooling season. If omitted, defaults to 75 F.

Design outdoor relative humidity as a percentage. Used to estimate latent ventilation load. Humid climates may reach 70-80%. If omitted, defaults to 50%.

Exposed roof area above the conditioned space in square feet. If omitted, defaults to floor_area_ft2 (top-floor assumption). Set to 0 for spaces below another floor.

Overall thermal transmittance of the roof assembly in BTU/hr-ft2-F. ASHRAE 90.1 typical: 0.03-0.06. Includes sol-air temperature correction internally. If omitted, defaults to 0.04 BTU/hr-ft2-F.

Multiplier applied to the total cooling load to account for unknowns, duct leakage, and future growth. Typical range: 1.05-1.20. Must be >= 1.0. If omitted, defaults to 1.10.