HVAC questions for new home build in Central Texas
I'm going to build a 4000sf 2-story with 2x6 ext. walls and spray foam (open cell, full fill) and unvented attic. Stone/stucco exterior, front faces East, and essentially no tree shade.
Initial bids for HVAC came in as high as $36K for the best Carrier Infinity heat pump (2 units). They offered to do an American Standard 14 SEER dual unit system for $16K+.
Kept searching for other bids, convinced I was being gouged. Found a reputable installer that quoted $11,500 for 3-ton and 4-ton Amana heat pump @ 18 SEER with 2-stage compressors and variable speed handlers. Similar price for high-end Rheem.
Not a single HVAC contractor (I've spoken to 5) has talked about manual J calcs. I suspect they're all using lazy rules of thumb without regard for my particular construction features. Some bids were for dual 2.5 ton units, and the one I'm most likely to accept is calling for a 4-ton and 3-ton.
1. Is the high-end Amana heat pump reliable?
2. Should I be concerned about oversizing?
3. Does a 2-stage compressor mitigate the risk of oversizing?
4. Do I need an ERV??? My builder is suggesting it's a waste.