New Subdivisions and Bare Minimum Furnaces

[Sergroum]

Hello.

This isnt really a new trend, it probably is just me who is getting to encounter this a lot lately. I'm finding more and more people with 4200-4400 sq. feet houses that have a 80,000 BTU builder installed furnace with them. So far, pretty much everyone who already spent a winter in the house claimed the heating was inadequate. And that's with a pretty mild winter.
Does anyone have any experience with this? Is it usually on board with the builders? As in, maybe they go the very minimum, but usually well within the requirements? Does anyone have any experience with a homeowner successfully getting the builder to put in a bigger furnace? What would be the process? Do a proper heat loss/gain calculation and go to builder with it? Is there any kind of publicly available documentation that drops light on general 'good practices' of this for Ontario?

[Admin]

Yes, the new F280 HVAC designs seem to undersize the furnace and AC to try to improve comfort by causing longer run times.  The builder is supposed to beef up insulation and windows depending on which SB-12 package they choose.

I have also seen cases where the furnace is undersized and struggling to maintain temperatures on cold days.

The HVAC installer follows the furnace sizing that the HVAC designer picks, based on their heat loss calculations.