Bruce, sometimes it is just one trade trying to be a hard case with the final product suffering.
I once found a brick chimney which was built around a sheet metal duct, insulation and all. Very apparent it was a case of seeing which contractor could be the biggest azz. The chimney was brought straight up from ceiling to roof and was corbeled over and around the duct which should have been moved.
Jim

__________________
Jim Luttrall
Mr. Inspector.net, Inc.
Allen, Texas 75002