One thing people can do (but again .. expensive) is have a conditioned attic space. Which means put the spray-foam insulation under the roof, not on the ceiling

One thing people can do (but again .. expensive) is have a conditioned attic space. Which means put the spray-foam insulation under the roof, not on the ceiling. This is because typically you've got the ductwork up there, and the insulation on them is maybe R-4 (if they're insulated at all). So in a typical house you've got a temperature of 68F in the duct, surrounded by 150-160F temps. R-4 insulation doesn't help much in that situation. But if they roof were insulated the attic space temperature would be in the 80's, so you'd only have about a 20 degree difference and R-4 could handle that.