Heat load help: err on smaller furnace size?
We are building a new home in Ohio- potential for very cold winters and blistering summers, but you never know what you are going to get from year to year. Has felt like Colorado this summer!
Anyway, new house will be 3400 square feet with good cellulose insulation (can get more detailed if you want), a Tamarack ghost whole house fan, lots of glass facing west and south, some north and east. We are window openers and prefer house fan to AC whenever possible. One fireplace. 7 people. Average appliances. Unfinished but insulated basement.
We were suggested a 100K BTU furnace by the GC's recommended (not required) HVAC guy. He made no mention of a heat load calculation. So I got online and attempted to do one myself. I tried two different sites, and unless I am really messing up (possible) the 100K BTU seems oversized. Heat load calc indicates 80K would be adequate.
Reading I have done indicates that undersized is actually better; yielding more "highway miles"-type usage, vs "city miles" cycling.
Would someone knowledgable chime in, please? I'll be happy to give more info as necessary. Thanks!