Los Angeles Climate Zone Load Calculator
Estimates peak heating and cooling loads for buildings located in Los Angeles County climate zones (CEC Climate Zones 6, 8, 9, and 10) using simplified ASHRAE Manual J / Title 24 methodology.
Results will appear here.
Formulas Used
Conduction (Cooling):
Qcond = U × A × CLTD
where CLTDwall = (Tout,cool − Tin) + 15°F (solar-air correction)
and CLTDroof = (Tout,cool − Tin) + 30°F
Solar Gain:
Qsolar = SC × Ipeak,vert × Awin × CLF
SC = SHGC / 0.87 | CLF = 0.55 (interior shading assumed)
Ipeak,vert = 0.50 × Ipeak,horiz
Infiltration (Sensible):
Qinf,s = 1.1 × CFM × ΔT | CFM = ACH × Volume / 60
Infiltration (Latent):
Qinf,l = 0.68 × CFM × ΔW (ΔW in grains/lb)
Conduction (Heating):
Qheat = U × A × (Tin − Tout,heat)
Total Cooling Tons:
Tons = Qcool,total / 12,000 BTU/hr
Assumptions & References
- Design conditions sourced from CEC Title 24 Part 6 (2022) climate zone weather data and ASHRAE Fundamentals Handbook 99%/1% design values for Los Angeles County.
- Cooling load method follows ASHRAE CLTD/CLF/SCL simplified procedure (Manual J equivalent).
- Building geometry assumes a square floor plan; actual perimeter wall area may differ.
- Solar gain uses a composite average vertical surface (50% of peak horizontal) to account for mixed orientations; south-facing glass will be higher.
- Interior shading (blinds/drapes) assumed; CLF = 0.55 per ASHRAE Table 26-36.
- Occupant sensible heat = 250 BTU/hr, latent = 200 BTU/hr (light office/residential activity, ASHRAE Table 1, Chapter 18).
- Slab-on-grade floor heat loss estimated at Ueff = 0.03 BTU/hr·ft²·°F.
- No solar or internal gain credit applied to heating load (conservative per Manual J Section 7).
- Latent ΔW: Zone 6 = 18 gr/lb, Zones 8–10 = 22 gr/lb (low-humidity inland LA climate).
- Results are estimates only. A licensed mechanical engineer should perform a full Manual J or energy model for permit and equipment sizing.