DavidR
4
If I was looking I would think that the setup folder would be the location I would monitor, but I rather think that they would be cleared when the update is complete. All you are likely to see would be the new files with the updated/new file properties, new volume and date of modification/creation, etc.
Whist avast does use temporary folders for some things, such as the c:windows\temp_avast_ recently there is another c:windows\temp\avast_ash2, but I believe that is more related to the avast Software Updater and mostly empty sub-folders.