Since the gypsum board and air seal materials will be nearly inaccessible once the insulation and exterior cladding are installed, the materials specified to join the drywall to other components must be durable and attached so that the long term performance of the system is ensured. A daylight walk through the building before the insulation and interior finish are installed will highlight holes and cracks in the air barrier that have been missed. Careful inspection and perhaps field testing before closing the system are particularly important because the air barrier system is not as accessible for repair or maintenance as with the other method. A major advantage of these systems is that the supplier is usually the designer, manufacturer and installer of the wall so that the building owner has to deal with only one firm if the walls do not perform as specified. They can be discovered by careful on-site inspection and testing.
Curtain walls are the only wall system where an air leakage standard has been in use for some time.
Less sophisticated in their approach than curtain walls, pre-engineered metal walls became very popular for warehouses and factories. As well, over the last ten years, attractive and functional office buildings, medical complexes, laboratories and research institutions have been designed and built with these systems, using conventional interior finishes such as drywall or wood panelling. Compared to curtain walls, these walls usually offer a potential for a more continuous and thicker layer of thermal insulation. The greatest architectural masterpieces of the past were masonry construction. There are ways to build modern masonry walls that have all the advantages, the beauty and durability of the masterpieces of the past.