linux - total disk space among directories

I have this structure in my linux filesystem:

/folder
...subfolder1
......temp/
...subfolder2
......temp/
...subfolder3
......temp/
...subfolder4
......temp/
...subfolder5
......temp/

And I want to get the total disk space that all the temp/ folders are using. I suppose it's something with df or du, but no idea on how to achieve it. I only need the sum of all the temp/ directories, not the other folders or files that may be in the subfolders. Any idea?

thanks!!