[stevehull]

Don't obsess on PV solar roof orientation. So long as a roof area is within 20 degrees of true south each direction, this still gives you 90-95% of true south solar power.

Mistake on triple pane. In your southern climate, you don't need it in the winter - money spent here is a FAR too long payback. Double pane is certainly enough - but buy good ones, not the locally built vinyl clad cheepos. But you DO need to pay attention to summer overhangs on east, west and southern windows to prevent solar gain (maybe this is where you meant orientation).

In your area, do NOT insulate slab as you need to bleed off heat in summer. Your ground temps are just not that cold in Mississippi.

Outside air moisture and interior humidity are your enemy. Put your dryer in a room with outside air inlet and seal it off with good closing (sealed) door. A dryer pushes some 500-600 CFM per minute out of the house and conditioned air pushed out means that air (humid/moist and hot) MUST come in as house is now a vacuum.

Two ERVs are a necessity with a tight home of this size. The ones you are looking at are great in bathrooms to vent moisture 24x7 and total also provide about 40 CFM total (low speed). When bathroom/shower is in use (DPDT switch to bathroom light), then HRV goes into high fan speed mode (total 80 cfm).

I would still do geothermal for ducted AC . . . . an open loop system. You need to put in a well anyway. That many minisplits gets you into expensive territory. I have recently bought from Ingrams and they have a very nice three ton GTHP for about $3100. Forget the thermal heated floors - you just do not get that cold to justify that cost.

I would do SIPS for roof as you get everything for not a lot of $ and will be installed in one day (roof decking, insulation, interior trusses, R40 foam and inside OSB). SIPS with 8 inch foam (R40) are easily available. You can get 12 inch, but your local conditions don't merit. You can span up to 40 feet with SIPS. Makes interior layout easy with no load bearing walls needed.

Infiltration is your enemy - not heat or cold. Build yourself a temporary blower door (or window) with an old HVAC squirrel cage blower and simple water manometer. I use dry ice for "smoke" to detect leaks.

If you are in a rural area, build a pond (discharge water from open loop geo unit into this) as this markedly lowers your home insurance. Home insurance goes WAY up in rural areas with volunteer fire departments. You will also get a discount for metal roof (good idea). A fire pumper can dip suction hose into pond. Pond got me a 30% discount on my home insurance . . .

Do you really mean "as efficient as money will allow"?

Why a fireplace? This is a true energy waster. Put in a good wood burning stove that has opening (and closing doors). You can see fire if you want to, but can close it up for more efficient use. - but make it small (24 - 36 KBTU/hr) as it will otherwise overheat the house.

Mazel tov!


Steve