Furnace in the attic?

I am planning to add another floor to my house and obviously will have to involve professional engineer to finalize the design but right now I am just trying to get ideas on stuff I would like to do.
Since the plan is to have this 2nd floor addition as rental apartment I am hoping to have separate HVAC system for this section.
Is it possible to put furnace in the attic? The attic will be unfinished but I could make small room for furnace/hot water tank to insulate it and minimize the heat loss. Also the ducts/water pipes would have to be insulated since they would be located in the attic as well.
Another challenge in this case I think would be running A/C tubing from the outside unit (which would be on the ground level outside the house) all the way up so the length would be much longer than usual install and would most likely require more insulating that regular install?
I am also considering insulating between joists as the case would be with live in attic and maybe having couple of heating registeres there to make sure the temperature is kept above freezing.
Doing this would give me separate heating controls for each section and I would not have to demolish the main floor to run ducts and water to the second level.
What do you guys think about it?

I think it can be done, we see AC units in the attic anyway. Access for servicing will want to be a consideration.

High Efficiency furnaces condensate as part of the combustion process. Insulating that attic space to keep above freezing is a wise decision. I had one freeze up on me where all the condensate tubing plugged up with ice and the pressure switch would not "make". I chose the option of wrapping all condensate lines with heat tape to prevent the problem from reoccurring.

kok328 said:

High Efficiency furnaces condensate as part of the combustion process. Insulating that attic space to keep above freezing is a wise decision. I had one freeze up on me where all the condensate tubing plugged up with ice and the pressure switch would not "make". I chose the option of wrapping all condensate lines with heat tape to prevent the problem from reoccurring.

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What are the rules on the condesate line or exhaust line, windows, eaves, doors, etc.

Please check with your local code enforcement as I am not familiar with Canadian codes. Although I wouldn't really expect them to differ too much from U.S. codes in regards to HVAC installations. Due to backdraft through ventilated soffits, doors & windows, the only feasible option is to run the exhasut & combusiton air intakes through the roof. Again, check with local codes to determine height of piping above roof line and distance of separation between exhaust and intake. Condensate is passive gravity fed so anywhere you can run the lines to outdoors or a drain should be acceptable. Use PVC for this as poly tube doesn't lay flat enough to accomodate total drainage.

They use a white pvc about 2 1/2" for both and they run them out close together and some places use a special fitting with a bell of some kind to seperate the two but use the same hole in the wall.
And what seems to be closer to windows and doors than what would seem safe. Maybe someone will come along with some answers.

Concentric piping is when they run both intake and exhaust out the same hole. Exhaust comes out the middle and intake pulls from around the edges of the cap. Keep 4-6 feet away from windows and doors. Windows tend to fog up if the exhaust is blowing near them. Also remember to slope the exhaust pipe back towards the furnace so it drains into the condensate drain and not outside where it could freeze and cause a slippery area. Proper installation and attention to detail always benefits the homeowner in the longrun.