Automatically change file group permissions to that of parent

I was working with /var/www for some web stuff. The group and user owner of /var/www is www-data (Apache). I wanted to be able to  work in in /var/www with my own user. So, I added myself to the www-data group with the command "usermod -a -G www-data myUser" and then I ran "chmod g+s /var/www -R" which now means that every file created under /var/www becomes part of the /var/www group, even files created by me.