I hear you, it's a single two-story house built in 2000, not small but smaller than typical developers build these days here. I added 18 inches of insulation to the attic, not much I can do in the walls. Double-pane glass. It's not drafty but seems poorly insulated as a whole despite being relatively modern and better-than-average quality. Houses in cold climates seem much tighter and better insulated.
For ATX, this capacity is entirely about the summer. Any winter performance is an afterthought.
That's for sure. It can get pretty hot and humid, not quite Houston-like but you spend some significant cooling capacity condensing water out of the indoor air as well.
Insulation works regardless of the climate though. A well insulated house will be much easier to cool down in Texas, and much easier to warm up in Alaska