I'm a home inspector and have come across this and I don't like it.
American Standard model # AL C1B060A9361AE, Yr. 2012
Cat IV, 60K, installed as a non-direct vent. I am looking for some real references as to why this setup is no good. I cannot find anything specific in the code books and I have yet to find the manufacturers installation instructions on this model. There are no nearby doors or windows to consider.
The vents are coming out a wall just above the deck so they cut a hole in the floor of the deck and built a box around it above.
Right now, I have recommended improvements in this termination on the grounds that the corrosive effects of the condensate in this confined space are going to eventually destroy everything that comes in contact with it, and in very cold weather there's going to be some serious frost problems.