Here is my question and I would like some technical opinions.
I had 3 different Manual J Heat Calc done and since I use basement as liveable space they calculated that space well, just with different variables for outside walls and concrete floor being below grade. 2 were around 63,000 and the other was below 40000. I did myelf and cam in around 62500 so I feel confident that is BTU heat loss I need to plan for. I do have opportunity to tighten up attic with additional insulation to maybe save 4000 BTU.
Current furnace is a Bryant 398AAZ 90+ input at 80k btu. So I assume output was 72k. Furnace serverd us well, but after 23 years the imfamous carrier secondary heat exchanger failure got me. I am loooking at carrier products again, so I can try to match ducts and AC as close as possiable to minimize labor durign replacement.
Here is the question. Should I go with 80000 btu at 95% which output would be 76,000 or the 60000 at 95% with output of 57000.
I guess is it better to be 13,000 high or 6000 lower.
Note: I live in Michigan and Low is 1 degree, since I moved in I upgraded windows to 2 ply gas filled and added 1/4 insolation over wood siding before I vyna sidded upper level. The furnace has seemed to short cycle and generate lots of condensation since I tightend up house. I have certified tech as good friend so I am going to be his helper on this job so I can get any tax credits and keep bryant warranty for cert tech performing startup.
Any expert opinioins would be appreciated