Waste..... Foaming the walls is a waste. Go to any green building forum and it is almost universally felt that foaming walls is a waste of money. The foam salesmen are about the only ones that disagree. In my east facing house with 2x4 fiberglass batts, the walls and attic only account for 20% of total heat gain (energy audit). You are going to spend $10k to make that 20% come down to 15%. I have a similar size house in NC and I spent about $20k on Carrier Infinity 15/16 with heat pumps and 90% NG furnace and zoning and humidifier. So I think the $36k is absolutely crap. But $11k is a bit ridiculous also given the specs. In fact- I just can't believe it. Manual J is required in NC by code - so I don't know what to tell you. It is standard around here for quotes/bids. Oversizing sucks. 2 stage helps compensate. An is an air quality thing more than anything else. It is rarely cost effective. Texas is big - what is your area and ideally what is your HDD and CDD? Here is what I would do - presuming you live in a 90% cooling area. - Build with 2x4s and sheath the house in 1 inch rigid foam. If it really hot, you could go to 2 inches of foam. - Focus on minimizing East and West windows. If you can't - then really focus on low SHGC windows. All windows are low-e nowadays but SHGCs vary considerably - there are basic windows at .2 and .45 - a rather huge difference. Overhang the windows as much as you can tolerate. Big deep porches. Do those things and you should be able to get down to 2 2ton units which you should be able to get for $10k for seer 15 or 16. Most people don't find it worthwhile to get seer 18 equipment. Usually with new construction, you can spend that $5k (or whatever) on shell improvements (windows, overhangs) and get a better permanent ROI. There is no disagreement anywhere that 2inches of rigid foam on a 2x4 wall filled with blown cellulose outperforms a 2x6 wall with spray foam (and does so at a lower cost). Lastly - why an unvented attic? Because the ductwork is there? The best practice is to get the ductwork out of the attic in the first place. It is cheaper and far more cost effective. My personal house (4000+basement) would cost $10k to spray foam the attic at a estimated annual savings of.... $70. How about that ROI....

I was thinking was socal said. You mention wanting "land for the kids", but often what kids want is access to other kids. I'm in an older suburb with smaller lots (e.g., 65-80' wide on average) and bands of little kids are always out and about in each other's yards, and mine. I love that! The trade off with having smaller yards is that my kids grew up in a great school district where they walked or biked to school, town, pool, parks, etc. - part of their lifestyle rather than being driven everywhere. It's nice for the parents, too, to have that neighborly support system when something comes up and the kids need watching. You may feel differently, but I'd caution that you make sure the land you want is for you and your spouse. Hopefully your kids will feel the same way, but if they don't at least you and your wife will enjoy the land.

Building custom vs. a tract home is always more expensive as mentioned by others. Buying existing can be more or less expensive depending on the area as it is very dependent on the market value of a home in the area. It essentially comes down to what are buyers willing to pay in the area, includes some adjustments based on location, features of the house etc. and the market value sets the house price of existing homes. This has very little to do with how much it cost to build the house to start with.

I hear what the pros say about tract homes. And I get it. But I've lived in SoCal so long.... it must be the mecca for tract homes. And though they aren't built like a custom home would be, none of the tract homes I've seen look like that. I would go check the other homes in the tract and see if others have that particular defect. If they don't, then the builder is more likely to agree to fix the worst of the problems. You can put up a fight and say you're not going to close.... but you need information to weigh all your options. Would they be able to sell this house for even more money if you backed out? Or would they stand to lose money? Do you know others purchasing homes in this tract? Can you chat with them to see how willing to fix the builder would be? Can you talk to some of the tradespeople to see if management is having them fix stuff? I would keep at it and fight as much as possible. I do not think those wavy walls are typical of any tract home that I've ever seen.