Premature failure of an insulating glass unit (IGU) is often due to a rapid permeation of moisture through the edge seal and into the air gap of the unit. The reasons for premature failure investigated by BRE are numerous; these often originate with difficult conditions on building sites. Glazing of units in factories offers the potential for higher quality work - BRE has developed good practice guidance to maximise the benefits of factory glazing. The guidance, prepared as this two-part Digest, is based on research and good practice. Part 1 introduces the subject and describes the types of insulating glazing units and production facilities. This part (Part 2) describes the packaging, transportation to site and storage of IGUs; their installation, protection in service and maintenance; and performance testing and monitoring. 8 pages.