A homes thermal envelope consists of three main layers; an air barrier, insulation, and weather-resistant layer.
An airtightness layer eliminates uncontrolled air passage and moisture and sound transfer. This requires airtight materials, sealing, and blower-door testing.
After careful joint design and construction, a blower-door test can identify remaining envelope leaks. Blower doors are frames with fans and pressure gauges that fit in standard openings.
Insulation protects us from the elements. It’s a house blanket. Only your budget limits insulation thickness.