The tankless water heater would not be in the attic... Also, the furnace would be responsible for heating the apartment only. The whole system is also on a backup generator.
Another thing I forgot to mention is as of right now, we don't have siding up, however the sheathing is sealed... (Zip system). I don't know if this would have anything to do with the moisture.
Just finished building a garage and we are putting an apartment above it. We were thinking about putting a forced hot air furnace and a tankless water heater in the attic above the apartment. There is really no where else to put it, but I didn't know if something like this was possible. Any...
I hired a company to insulate the garage I just built because surprisingly it was just a hundred or so dollars more to have someone else to it... They put in R-19 unfaced insulation and then covered it all with plastic. A couple weeks later I noticed frost on the inside of the plastic cover...