First of all, don't expect the builder to do anything for you except raise your blood pressure.
My builder used Krugar (sp) for installation and they are not allowed on my property. We've had 2 fires (defective outside lighting), a gas leak (Krugar)...we had to leave immediately and a crack in the furnace which again....shut us down and we have to leave until it was repaired due to possible fire and/or carbon monoxide issues. No one associated with my builder is allowed to come on my property, warranty or not.
We built a Highland in 2000. The builders typically cut any corner possible to make extra $ for themselves. We have practically re-built this house. The A/C & heating units were undersized for our house. We got new, better systems, new furnaces and tweaked the returns and the difference was amazing. We used Collin Air and they are very fair. My DH installed new Hunter fans in all the rooms as well.
Also, our attic lacked sufficient insulation. This summer, my DH added about $2000 worth of insulation and it has made a world of difference.
We completely re-did and upgraded the garage doors and openers last month.
Now, if you are not planning on staying in the house for a good period of time, you might not want to spend the extra money like we have. We shopped around for other builders and other locations before we decided to keep what we have because we adore our huge treed private lot with wildlife as well as our house plan.
Good luck!
Susan