I am a bit late, but I can help you with carbonneutrality.
first:
dont buy outboard gear. the energyefficieny factor of musical gear is terrible :D
second:
dont buy a mixingboard (except SSL duality witch is a very green console).
for the building:
make the isolation better, so you have less heating, cooling going on. that would be a house like the "minergie-standart". "low-energy-houses" is the keyword.
we develop a tool to calcualte the alternative heating for such houses (and normal houses too). checkout
Vela Solaris - START it helps to calcutate the size of the collectors (for heating the water), the pump , the flowratio.. everything. it has housemodels inside, sunstandmodels..
it's not more costeffective to build a good isolated house (at least in europe). try to avoid the normal american-buildingstyle (TRY TO HAVE Concrete ground and brick-walls). the isolation need to be
air /outisde==> Brick/isolation /air/isolation/inner wall
in principal it0s a room in room constrution. the energyprincipal is based on the airflow. you need airflow transport systems, because the house is so isolated, you don't have enough natural airflow. but because you are american/studioowner, you will have a climatics-systems anyway.
hope that helps for the start.
cheers