I live in a 1904 house in Los Angeles and use my furnace about two months out of the year. I installed a new forced air furnace in the basement about 2 yrs ago, one big enough to heat the entire house, 4200sq ft. Unfortunately the bottom floor is the only floor that has venting and during those cold spells the 2nd story gets pretty chilly at night. I want to pipe heat into the attic, then into a larger breakout box that feeds three rooms upstairs.

There's an unused chimney running thru the center of my house, right past the kitchen. It starts in the basement and goes straight up to the attic then out thru the roof. I was wondering if I could run a sleeved heating duct up that old chimney then come out in the attic. I could seal the top of the chimney if need be. Is this a safe way to bring heat upstairs, safe and hopefully legal??

I want to put my space heating days behind me. I bought this super high efficient heater large enough to heat my house, it would be nice to finally get to use it for that...