Is it safe to delete folder com.apple.appstore? I am running extremely low on disk space and trying to clean up my Mac. Disk Inventory X shows me having over 20gb of space in .pkg (installer package) files in 
    /private/var/folders/pj/_(random)_/C/com.apple.appstore/*

I am wondering if these are safe to delete (they are in /private after all)? However I really don't want to give up 20 gigabytes to installer files.

Also, is there any built-in way to delete them (meaning through appstore menu or something, not via finder)?
That is the Download folder for App Store; where it saves apps as it downloads them.

It should be perfectly safe to delete them.

However, I have to say that it is a little strange that the files aren't being deleted automatically, either when you close App Store or when you restart - that is what I would expect. I haven't come across a case where they build up over time.