Can I modify the vent from my high efficiency furnace to prevent possible damage to the exterior of my home?
I am a Local HVAC Tech in the Toronto area. As stated, this exhaust is not installed according to local codes and the manufacturers installation instructions. There is no surprise that you are getting freezing condensation on the brick of the house. The reason for having the vent terminate straight out and away from the building is to avoid this. The facing of the brick will chip off after a few years of this. Another issue i see is that any exhaust for a high efficiency gas appliance must be insulated when being run in an unconditioned space (such as in a garage or running under a deck). Now if the termination is 2ft or less, you do not need to insulate the exhaust. However, in your situation there is a long termination, which requires it being insulated to prevent freezing. 

My solution would be to cut off the tee at the end of the termination, slide on armaflex pipe insulation around the exhaust. You should have from where the tee started, to where the pipe enters the house fully insulated. Then using system 636 PVC glue and primer if doing it in cold weather, glue a system 636 PVC elbow onto the end of the termination so that it is blowing the exhaust straight away from the house. Then cut a 6" piece of system 636 2" PVC pipe and glue that into the elbow to help throw the exhaust further away from the structure. Doing all of the above would solve all the termination issues, and bring it back up to code.