[alricb]

I don't really think it's the case. You're adding surface area, yes, but not that much, and you can easily compensate by being more careful with windows and avoiding wasteful features like bumpouts &c.

On a 35*50 (1750 sq. ft) single level house, you're adding 170 ft of exterior wall to an envelope that had 1360 sq. ft of walls and 1750 sq. ft of ceiling giving directly on outdoors, or 5.4%. Given a "code" insulation level of R-20, it would mean adding less than an inch of insulation to compensate.

I suspect the builders from warmer climates simply didn't build correctly for the climate: not enough insulation, problematic details. You get issues whenever builders move from one climate to another, because many of them just don't care enough to learn about how to adapt houses to their new climate. Details that are fine in one climate (if you're living in a dry enough place, you can install your windows almost without thinking) won't work in another (install a window "Vegas-style" in Seattle and see how long it takes before it leaks).

[auxym]

It's not a question of surface area, but that the air you're paying to warm up will all go right to the ceiling. You can easily get temperature gradients of at least 5 C on a cold day with a two-story high open set up. That is where ceiling fans come in, though.

[lsaferite]

Or a passive house design.