Air duct sizing for suppling combustion air to oil furnace 1

[SteamBryan]

I have on old house heated by forced air oil furnace. The furnace is in an unfinished part of the basement which does not have an air duct that comes from outside to feed the furnace. the duct going from the furnace to the cheminey is 5" dia.
I see different duct designs to bring in the air, but they all seem to be give lots of cold air to my unfinished basement.
Does anybdy have a good design for a duct that will not make the unfinished section uncomfortabily cold?
Bryan

 

[cdxx139]

Old furnaces are not direct vented, so you have to provide air to the space. I design to run the duct so it ends at the combustion air fan, hoping to minimize airflow to the space, (but it will).

You can put a damper on the inlet, and interlock it with the boiler, so it open when the boiler is on, and shuts when the boiler shuts.

You can enclose the boiler in a boiler room, and insulate it from the rest of the basement

All heating equipment needs combustion air, unless you upgrade to a direct vented gas boiler (utility companies are giving nice rebates for this now). Or go with an electric boiler (dont do that)

knowledge is power

 

[chicopee]

All residences that I have seen in the N.E. did not have make up air ducted from the outside. In residences, there is enough air leakage thru the structures not warrenting duct systems espacially if the basements are wide open.