Avast scans stuff when computer is idle

Is there any way to disable this behavior?
Whenever I leave my computer, after 5 minutes or so the I hear the fan spinning like hell and apparently it’s Avast scanning.

I don’t want this. I find it completely useless. Waste of energy for no benefit. The point of having an antivirus is to scan NEW files, not the same files over and over again.

this is how antivirus realtime protection works … any file that moves when computer is on, is checked by the antivirus

I hear the fan spinning like hell
have you dusted your computer? do you use screensaver?....have you selected avast screensaver scan? do you have more then one antivirus installed?

the computer is new, i dont think dusting is a prob.

How to disable screen saver scan? I don’t have a screen saver in Windows.
But the option in avast cannot be disabled?! I unchekced loop scanning and checked Do not scan if running on batteries.

I only have one antivirus.

The high-cpu usage and avast icon animation stop immediately when computer goes out of idle.

Maybe this is the automatic Windows maintenance which is only running when the computer is idle.

is windows index running?
http://windows.microsoft.com/en-us/windows/improve-windows-searches-using-index-faq#1TC=windows-7