Definitely the right move with the open celled foam for the whole house. The insulated garage doors really help to keep out the heat / cold, including the radiant heat transfer from the sun if your garage doors will face the sun at some point during the day. I would likewise stay away from the all-electric tankless. I believe the problems are linked to mineral build-up over time, particularly if you are on well water.
Let me see, what would I do / do differently? Here are some of the top items:
1. Use all engineered I-joists for the floor joists and no natural timbers for a dead-level, strong and even floor
2. Use 3/4" tongue and groove plywood vs. OSB for the subfloors (much stronger)
3. Increased the amount of low-voltage wiring in the house, including a Gigabit network (Cat-6 wire) at every network port and two at every TV location for future use
4. Installed a chandelier lowering motor in the attic for our entryway chandelier to be lowered for bulb replacement/cleaning
5. Use a jackshaft garage door opener vs. the standard - http://www.liftmaster.com/consumerwe...px?modelId=834
6. Install networking wires at your thermostat and security panel locations!!!
7. use open cell foam on the backside of the ceiling drywall (i.e. the second floor ceiling) to an R30 level, then blown in insulation to top everything off to an R-50 to prevent air escaping and resist heat in the attic from coming into the top floor
8. If you have a gable roof....getting 3/4" plywood flooring down and access to some of the attic space for extra storage
9. A dedicated sub-panel for the basement actually located in the basement
10. Underground piping to clear collect downspout roof run-off and discharge away from the house
11. Adding 2" rigid foam and/or radiant barrier on walls behind the brick (with a small air gap if possible - this is a HUGE thermal load of sun-heated brick trying to transfer heat into the house. These methods will help kill a lot of this heat load before even reaching the open cell foam in the house
12. If I wasn't using SIPs, then use 2x6 framing at 24" OC (known as advanced framing techniques) to increase insulation depth (5.5" vs. 3.5") and amount (through less vertical studding). Uses about 15% less total lumber as well.
Those are the main tips of if I were to build a house again. If I think of any others I will let you know but these are the primary energy efficiency / convenience / preventative / upscale features I would have for building the house again.
When are they delivering / installing the weeping tile pipe? I don't understand exactly how your vertical piping system will reach into the weeping system and kill roots. If the plan is to use some sort of "T" connector between the 1.5" PVC and the weeping pipe, you must make sure that the connection is also covered by the protective sock as to not allow soil infiltration that will clog your weepers. Anyhow, good luck over the next week with the backfilling!