Dante M. Catoni wrote:

I just purchased a house that was built in 1935. It has the original steam
radiators and coal boiler that has been converted to natural gas. I would
like to put in a high efficiency furnace and then someday add central AC. I
was wondering how big the exhaust pipe is on a newer furnace (the house is
about 1700 sq ft living area) and if it's possible to vent it out the side
of the house near the foundation instead of the roof. The reason I ask is I
would be able to remove the chimney from the house and run the ducts to the
second floor through that space. If that were possible the only finished
area of the house that would need to be torn down to install the ducts is
the back wall of a small kitchen closet which I could sheetrock and compound
in about an hour. Then of course repair the hole in the roof. Everywhere
else in the house has full access and installing ducts would actually be a
lot easier than baseboard heat.

Thanks
Dante



Yes. A typical side-vented unit only requires a 2" vent
(maybe 3" on larger units).

http://www.williamson-thermoflo.com/boilersw.htm
Look at the GWI just as an example.

You'll want to give some thought to domestic water heating
appliance as well.

Jim