Group text with an international number

I just got a french number as I am living in France for the next year. However, I am part of group messages based in the States and this new french number is now in the group chat. My email is also in the chat as I was hoping i could imessage though my email. Since the french number is in the chat- is anyone getting charged for texting an international number? Or is it all going through my email on imessage? I just want to make sure none of my friends are getting charged for being part of a chat with a french number.