Quick preconstruction feasibility: estimate HVAC tonnage, electrical service size, generator capacity, plumbing demand, fire protection, and space requirements by building type.
This tool uses published engineering rules of thumb to estimate MEP system sizes for preconstruction feasibility. These are order-of-magnitude estimates — not engineering calculations. They answer "how big are the systems?" before detailed design begins.
When to use: Early project pursuits, feasibility studies, space planning, utility coordination. Not for final equipment selection or permit drawings.
Accuracy: Rules of thumb are typically within +/- 25-30% of final engineered values. They are intentionally conservative (slightly oversized) for budgeting purposes.
Sources: ASHRAE Handbook of Fundamentals (Chapter 18), ASHRAE Applications Handbook (Chapters 9, 17, 22), NEC Article 220, NFPA 13/14, industry preconstruction benchmarks. These are industry estimates intended as starting points — verify against your project-specific conditions and local engineering practice.
Climate adjustment: Cooling loads are adjusted by climate zone. Hot-humid climates add 15-25% to cooling tonnage. Cold climates reduce cooling but increase heating. The tool shows both the base rule and the climate-adjusted result.
Code Edition Notice: Sizing rules reference ASHRAE Handbooks, NEC Article 220 (branch circuit/feeder calculations), and NFPA 13 (sprinkler head spacing). These standards update on 3-year cycles. Fire protection head spacing uses NFPA 13 ordinary hazard values (130 SF/head) — your AHJ may enforce a different edition with different coverage areas. Electrical service sizing uses demand factor estimates, not NEC Article 220 load calculations. Generator sizing percentages are planning estimates, not NEC 700/701/702 requirements. Always verify system sizes with a licensed professional engineer and confirm code editions adopted by your Authority Having Jurisdiction (AHJ).