Hi: I'm trying to size a new upflow heater to existing non insulated sheetmetal system in attic. The old heater was removed from storm Sandy. I used a online calulater and got 49000 BTUS. There was no consideration for attic ductwork.
Its only a 1000sf house and owner does'nt want to insulate ducts. Anyone know the addition heat loss from above ducts.
thanks...