❄️ HVAC SIZING (rule-of-thumb)
Quick BTU/hr estimate. Manual J is the real deal — this is napkin math: square footage × climate × insulation × occupancy + sun load. WI defaults baked in.
SQ FT
CEILING (ft)
CLIMATE ZONE
1 - hot/humid (FL/TX gulf)
2 - hot (TX/AZ/SoCal)
3 - warm (TN/NC)
4 - mixed (KY/VA)
5 - cool (PA/IA/IL)
6 - cold (WI/MN/UPMI)
7 - very cold (northern MN)
INSULATION
poor (pre-1960)
fair (1960-90)
good (1990+)
excellent (passive house)
WINDOWS
few/triple-pane
average
many/single-pane
SUN EXPOSURE
north / shaded
balanced
west/south facing
OCCUPANTS
KITCHEN/HEAT-GEN APPLIANCES
few
typical
commercial-grade
SIZE