To supersede the requirements of Sentence 3.2.3.2.(1) and state a different [less onerous] method for calculating the area of an exposing building face, if certain conditions are met, on the basis that the conditions provide an equivalent level of protection.
This [the conditions] is to limit the probability that an entire exposing building face will be involved in a fire, which could lead to the spread of fire from the subject building to an adjacent building, which could lead to damage to the adjacent building.