I just took my home plans to the county building department to begin the plan check process. I noticed (a little late) that the architect had indicated a 90% furnace. My plans had been to get an 80% furnace and a higher SEER AC given my area which has mild winters and hot dry summers.
My understanding by reading some posts here was that, unless money is no object, you should match the higher efficiency unit (AC or heating) to your most extreme weather condition. So if my winters are mild I would not necessarily benefit from a higher efficiency furnace as much as a higher SEER AC to deal with my hotter summers.
When I asked the building permit technician if the architect's specs for a 90% furnace could be changed he told me I would have to have another energy calculation.
Does this sound right to you? Is there a connection between an energy calculation (Manual J) and the efficiency ratings of the equipment?
I thought, perhaps in error, that the calculation had to do with capacity, not efficiency.
In any case, I left the plans and will ask the architect on Monday.