This is a metal housing for your furnace and/or water heater.
It is called a Van Packer Flu. 
This housing was standard in the 50’s and 60’s. It is always a problem area in that
it cannot be properly flashed around and eventually will leak.
As shown in this picture, there is an abundance of tar placed around the base of this housing to try and temporarily prevent further leaking.
We can remove the obsolete housing and install the proper size and type of double wall pipe with the proper flashing,
so you will not have leakage, as shown in the picture below.
The wall shown here is termed a sidewall. It is where each row of shingles meet the
wood or fiber cement siding. 
Frequently, this bottom edge of the siding is not painted where it meets the roof line.
This in turn causes a capillary action and the water is absorbed into the siding. The long terms effects of this situation are obvious, especially during the tear off phase of the roof. The shingles are seated underneath the siding. When the shingles are removed, it is most likely some of the siding WILL be damaged if this capillary action has taken place.