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What size furnace for new construction?

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.

Re: What size furnace for new construction?

Did you ask any of them if they did a Manual J? The size of the furnace is the size that is needed to overcome the heat loss. Remember though it's not the input of the furnace it's the out put. a 70,ooo btu furnace at 80% is 56,000 btu's

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