Sometimes I have to replace entire home systems. Such is the case below where I had to replaced the owner’s HVAC system. His old system had been damaged by fire. In addition, he chose to move walls, which required going to a two furnace system.
When you have ducts that are exposed to non-treated air (such as the attic) you will get condensation which can manifest itself in several ways including: roof leaks, water on drywall, and mold.
To solve this problem it is necessary to install insulated ducts. These look like giant clothes dyer vent hoses.