Insulation and air sealing

Continuous layer

Insulation between ribs leaves thermal bridges through steel. Prioritize roof, sun-facing panels, rear/side doorsand cab boundary while preserving drainage and safety systems.

Air leakage

Seal uncontrolled gaps that bypass insulation, but do not seal factory drainage, pressure relief or requiredcombustion/vehicle ventilation. Door seals need inspection and replacement, not expanding foam.

Windows dominate

Glass typically has far lower thermal resistance than insulated walls and admits solar radiation. This is whyexternal covers can outperform another thin wall layer during direct sun.

Moisture-safe assembly

Warm humid air can reach cold metal and condense behind finishes. Use compatible vapor/air-control details,corrosion protection and drainage; do not trap wet insulation against steel.

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.