Most GC's building track resi are in the volume business. Most buyers only know a few questions like what's the insulation rating or how long is the warranty. A GC can brag about the things they know will be asked and ignore the rest. Recent studies claim flex run in a unconditioned space can use 20-25% more energy. But it's cheaper than thinking a better solution. I once asked a large GC who always took the low number "How do you control quality?" He looked at me as if I had two heads.
On a brighter side there is a multi-state GC building homes here that works for high energy ratings. Apparently energy savings is selling for them. Until the customer demands a better building GC's will still dodge energy issues and distract buyers with granite counter tops. It's called by sales people as "Selling the sizzle instead of the steak."
"What Fools these mortals be"....Puck