To exempt foamed plastic insulation installed in ceiling spaces from the requirements of Sentence 3.6.5.4.(5), which would otherwise prohibit its use, if certain conditions are met.
This is to limit the probability that foamed plastic insulation will not be protected by a thermal barrier, which could lead to the insulation contributing to the growth or spread of fire, which could lead to the spread of fire to other parts of the building by means of the ceiling space, which could lead to harm to persons.
To expand the application of Article 3.1.5.14. [more specifically Sentence 3.1.5.14.(4)], which would otherwise apply only to buildings described in Sentence 1.3.3.2.(1) of Division A that are required to be of noncombustible construction.