The department and any local code authority may conduct inspections and investigations necessary to enforce the Nebraska Energy Code or equivalent code and may, at reasonable hours, enter into any building and upon any premises within its jurisdiction for the purpose of examination to determine compliance with sections 81-1608 to 81-1626. Inspections shall be conducted only after permission has been granted by the owner or occupant or after a warrant has been issued pursuant to sections 29-830 to 29-835.