A grade 1 install is a measurement given when insulation is installed properly and without any significant defects.
Watch Video: NAIMA Grade 1 – Proper Installation of Insulation (https://www.knaufinsulation.us/en/videos/pre-insulation%20walk-through)
https://insulationinstitute.org/im-a-building-or-facility-professional/residential/installation-guidance-2/grade-1-installation/