Manual J Cooling Load (Simplified)
Simplified sensible and latent cooling load estimate.
Example
You enter
- Floor area (ft²) 1500
- Above-grade wall area (ft²) 1200
- Window area (ft²) 200
- Ceiling area (ft²) 1500
- Insulation level average
- Window type double
- Occupants 4
- Outdoor design temp (°F) 95
- Indoor design temp (°F) 75
You get
- Sensible 16450 BTU/hr
- Latent 4055 BTU/hr
- Total cooling load 20505 BTU/hr
- Tons 1.7088
- Sensible heat ratio SHR 0.8022
Details, formula, and sources
Sensible cooling load = U×A×ΔT + solar gain + internal gain + infiltration. Latent load = 0.69 × CFM_inf × Δgr (grains/lb). Simplified estimator only; ACCA Manual J 8th ed. is the code-compliant method.
ACCA Manual J, 8th edition. NOAA NCEI cooling design temperatures by location (public domain).
ACCA Manual J licensed; principles free in published HVAC engineering texts. NOAA design temps free at ncei.noaa.gov.
Estimate. AHJ and licensed mechanical contractor govern. ACCA Manual J / D / S supersede rules of thumb.
Field names used by the API: floor_area_ft2, wall_area_ft2, window_area_ft2, ceiling_area_ft2, insulation_level, window_type, occupants, outdoor_design_F, indoor_design_F, sensible_BTU_hr, latent_BTU_hr, total_BTU_hr, tons, SHR
- Indoor design temperature 75 °F unless user suppliesACCA Manual J 8th ed. typical
- Outdoor design temperature data/hvac/climate-data.json keyed to location (NOAA NCEI 99% / 1% values)NOAA NCEI
- Air density factor 1.08 BTU/(hr × CFM × °F)ASHRAE Fundamentals by name (sea level, 70 °F)