Assuming unsealed opening between wall and roof deck was observed on site.
Conditioned air is escaping or outside air is infiltrating around gaps between the building wall and the building roof. In either case heating energy is lost, comfort is reduced (drafts in winter), and the life expectancy of building components is reduced by the uncontrolled migration of air and moisture through the building envelope.
A commercial grade spray-in-place foam should be applied around the entire roof-wall joint of the building / in xxx, where accessible. The foam must be capable of forming an air barrier, and must be installed by a qualified insulating contractor.