furnace sizing

[Hp]

how to size a high efficiency 2 stage furnace replacing a single stage 90,000 BTUs natural draft furnace. How many btus needed for new high efficiency furnace

thanks

[Admin]

Where is the house located and how old is it?  And what is the input/output of the existing furnace?

Without a heat loss calculation it won't be scientific but I can probably get you in the right ballpark.

[Hp]

its in Malton and build before 2000. 90,000 input to 82,ooo btu out

[TexMex099]

other calculations are typically done like duct sizing, sq footage and heat loss but if youre replacing it with lets say a 96 AFUE furnace then an 80k would output 76800k which is close to the output of your old appliance on high fire.

THATS JUST A GUESS, never just plop in whatever the last furnace was cause you dont know if THAT one was sized correctly