The reason I dont pull air from inside is I would loose all my CO2 and the system would not be sealed.You could pull from out side and then out a roof vent .. All houses have 120/240 v 240 v is 2 hot 120v and no neutral/ (white wire in most cases) You just need a double pole breaker and run two wires off the breaker and you have 240v it lowers your amps in half at least, its the amps you pay for..I have been a state certified electrican going on 10 years the biggest scam that electrical company's have is 120 volts it draws way to much amps.Most people shy away from 240 v for some reason they dont even realize they have it .When I did an amp test on my new sub panel it was drawing 29 amps with everything on I ran a 100 amp sub panel beacuse I had it and if I ever wanted to add anything else I would not have to worry.I will take some pics of the duct work and exhaust fans along with the electrical panel...
Hope this helps...