I thought I could delve into this topic like an engineer or architect, showing: heating degree-day isotherms, cooling degree-day isotherms, and mean annual temperature maps. But, alas, the graphics just don't work at blog-format. What else, then?
Turns out that, for the USA at least, plant hardiness zone maps get the overall idea across much better. They've already been adapted to a changing climate, courtesy of the Arbor Day Foundation (as pictured). Answer to the question of who needs extreme insulation is....drum roll......Everybody.
If you live in the hottest cities - Key West tops the list - you need lots of insulation to stay cool, and to minimize your coal-fired electric bill.
And in the coldest cities - International Falls MN is the epitome of cold in the lower 48 - you need extra insulation to avoid that 'colder than a frog's bottom in January' feeling, and to cut those heating bills.
In between, you just need it for both reasons.
As TreeHugger Lloyd likes to say: "Insulate Baby... Insulate."
Now, the flip side of this question will be: who most needs government incentives to add more efficient HVAC systems; and, who needs government incentives for more efficient heating systems?
The answer is....drum roll....