"Each compliance path may have mandatory, prescriptive, or tradeoff requirements. ... Prescriptive requirements are requirements that either must be met by every building design, or if the requirement is not met, a tradeoff must be made to “make up” for not meeting that requirement."

Where I live, if the house isn't up to code, you can't get a certificate of occupancy. So why would one "close" when one can't inhabit the house?

YES. Central Texan (Austin) weighing in. Code in TX is there for a variety of issues, energy efficiency not the least of it. If the inspector says "nope", stop, get your contractor to fix it and don't look back. Do it now, while it's open and still "fixable" without tearing your walls/ceilings/drywall apart. If you ignore the inspector (and if you have a standard TX Builder's contract) the "fix", when needed, could fall on your pocketbook.

I suspect that "our inspector" is a private inspector that you hired, and not a city or state inspector.

"does anyone know a builder loophole that allows for R6 when R8 is code?" - hopefully, my previous post gave you some insight into that. Insulation values are "prescriptive", not "mandatory".

@Kathy - the mind boggles. A builder ignoring code on not just one house but a neighbourhood.

Maybe Fred has the best idea (if I understand his suggestion - upgrade the insulation around the R6 and it will meet code).

Something also to consider- HVAC, what's the SEER rating? Find that out- important, since the higher the SEER, the more you'll need 8 vs 6- at least.

Now it's time to ask/determine (as you may already know) if these ducts are in conditioned or non-conditioned spaces. Makes a difference. SEER 16 can benefit from either, plus blown in insulation. But the last thing you want is to get stopped at the City inspection level, with something "off". That's a contractor chat.

Be friendly, but firm. If you have a TX Builder's Warranty, that contractor know that if it goes wrong, (after accepting work) it's all on him, to fix. So what, really? You just want this done right, the first time.

I'll tell you that for my last build, HVAC was huge in everybody's window- do it right, the first time. I was looking for quiet, energy efficiency. Contractor was looking not to be on the hook for years, within anything that failed, there.

We worked together, got a great outcome.

Good luck! Stay strong. It matters, in the end.

Yes, that is one of the methods for ensuring that a "tradeoff" is made for the "prescriptive" requirements that I posted earlier. Another is in Section R406.