dont really know if any harm can be done, sure some body will tell me) but
i experimented on my own consevortary , inside and out
i used m/spitters just sprayed on ,and wiped off came up a treat,
even inside of the roof just spayed, and literaly sea the dirt running down in beads. worth a try ??
unless im told different, but i cant see how if safe on carpets , sure must be safe on upvcregards geoff