I’ve been using avast! Internet Security for the past year. Avast IS 8 NEVER turned off the Windows firewall. Avast IS 2014 (2006) turned off the Windows firewall SOMETIMES (probably more accurate to say that it took control of the Windows firewall). Avast IS 2014 (2007) NEVER turns off the Windows firewall.
The interesting thing, at least for me, was that version 2006 prevented a program I use daily from working. This only happened when avast IS took control of the Windows firewall. Since installing avast version 2007 the problem I had has been fixed.
Based on the above, although I am not an expert by any means, I would think that the avast firewall is back to what is used to be in version 8.