AC Sizing

Two-story homes often need better return paths because upstairs rooms can become pressure isolated when doors close and duct runs are long.

Sunrooms often need special load treatment because glass exposure can dominate the cooling load.

Open floor plans can still feel uneven when solar gain, kitchen load, returns and thermostat location are not balanced.

Vaulted ceilings can increase cooling load and comfort risk through volume, roof exposure and stratification.

Ceiling height matters because taller rooms contain more air volume and often more wall or roof exposure, but it is not a stand-alone tonnage rule.

Better attic insulation can reduce cooling load, but the AC size should be adjusted only after the full load calculation is updated.

A west-facing room can need more cooling late in the day because afternoon sun adds solar heat after the rest of the house may be near setpoint.

Window heat gain can increase AC load because glass adds solar gain and conductive heat that square footage alone misses.

A 4 ton AC is nominally 48,000 Btu/h of cooling capacity, but delivered cooling depends on conditions, airflow and installation.

Cooling design temperature is a local sizing condition, not the hottest temperature the city has ever reached.