I apologize as I would imagine this question cycles often. I am frustrated trying to accurately decide what size furnace I will need for a new construction cabin in northern WI. I already have a REScheck completed stating a Total Building Heat Loss of 36,113 BTU/hr. The bids I've received from HVAC installers have been for 70,000-75,000 BTU/hr units. I'm suspicious that their calculations were merely taking my heating zone x square footage. I've done the on-line calculators for heat-loss and have come up with a range from 40,000-67,000 BTU/hr for my project. Should there be a correspondence between the REScheck and the Heat-loss calcs? I know ultimately I should do the schedule 'J' calculations, but I'm a greenhorn with HVAC. Any advice would greatly be appreciated.