For this example using an 80 efficient furnace the 1900 square foot home above would require a 90 000 btu input furnace that produces 72 000 btu s of heating which is close enough to the 76 000 btu s required using the climate heating factor.
60000 btu furnace square footage.
Btu charts furnace output and air conditioner size for a bungalow bungalow area sq ft furnace output btu hr air conditioner size ton built after year 1980 built before year 1980 built after year 1980 built before year 1980 up to readmore.
With a less efficient furnace operating at 80 percent efficiency this would require a.
2 000 square feet x 40 btus 80 000 btu output required thanks to the equation we know we need 80 000 btus of heat.
A more efficient furnace will output more btus of heat than a less efficient furnace with the same btu rating.
A mid sized home of 2 000 square feet would need approximately 50 000 to 60 000 btu to heat it properly.
For example if a furnace is rated at 100 000 btus and is 80 efficient then the heat output will be 80 000 btus 100 000 x 8.
A 60 000 btu furnace will adequately heat most mid size family homes in zone 1 and zone 2.
On the other hand the colder zone 5 climates of the northeast upper midwest and pacific northwest demand 50 60 btus per square foot for maximum efficiency.