Ventilation mode vs A/C mode

Vent mode

When outdoor air is cooler/drier than inside, turn A/C off, open planned intake paths and use the roof vent/fansto purge heat. Night flushing can remove stored heat before sunrise.

A/C mode

Close windows/doors, turn the roof exhaust fan off, fit exterior covers and circulate interior air. Exhaustingcooled air forces equally warm humid replacement air through leaks.

The muscle-memory mistake

After months of roof-vent living, switches become automatic. Label the controls or interlock/automate them so'A/C ON = roof exhaust OFF.'

Fresh air

An occupied van still needs safe air quality. Brief planned ventilation adds load but may be necessary;combustion appliances must be installed/vented exactly as required. Never trade carbon monoxide safety fortemperature.

System rule

Do not judge a cooling upgrade at the vent. Judge it by the hottest occupied zone, humidity, energy usedand whether the system can recover that energy safely.

CHAPTER CHECK

• I can explain which heat path this step addresses.• I measured its effect at front, middle and rear - not only by touch.• I added its power, failure mode, maintenance and safety action to the system plan.