acl should work.
Are you using it right? Giving recursive rule for existing files and default for new files?
sudo setfacl -Rm d:g:<user-group>:rwX,g:<user-group>:rwX /var/www
Will give your main group rw permissions on files and x on the directories (to enter them).
-m: modify existing rule (used to modify the existing permissions)
d:g:...:rwX: this indicates the default part for new files/directories
g:..:rwX: group to use for the acl
rwX: read, write and change directory allowed (rwx will allow execute on files too)
The command has two parts:
d:g:..... before the
g:.... after the
The 1st one (
d:...) will assign the default for new files/directories and the 2nd one (
g:...) will modify existing files.
Obs: you can also use acl for users (with u:) or other (o:) instead of groups (g:)