To exempt certain buildings from the application of Articles 3.2.2.20., 3.2.2.23., 3.2.2.24., 3.2.2.29., 3.2.2.31., 3.2.2.36., 3.2.2.37., 3.2.2.38., 3.2.2.39., 3.2.2.48., 3.2.2.54., 3.2.2.62., 3.2.2.68., 3.2.2.72., 3.2.2.73., 3.2.2.78., and 3.2.2.80., which would otherwise require the roof assembly to be of noncombustible construction, and permit a roof assembly of heavy timber construction.