Heating/Cooling a new addition

[paesundling]

I am converting my 3-season room (den) into a year-round living space and will need to heat and cool it. I live in Indiana. I am on a slab and have a down-draft furnace and a central air unit. I was wondering if I could somehow tie into the ducts without having to rent a jackhammer and get into the foundation? The room I am working on is about 30 feet away from the furnace...would it be possible to tap in direct to it? Also, I understand I am adding 200+ SFT to the house so sizing up the furnace something I plan to look into. Thanks for all the help!!!

[builderelements]

Any attic/above ceiling space to run ductwork?

[paesundling]

sorry it's taken so long to respond...I have a 3' overhang area (from the original house) that has plenty of room to run ductwork...I just don't how exactly to tap into the furnace? And about 20' would need to run through an uninsulated, unheated garage and about 10' through the overhang that runs outdoors?