In article , "Ian White"
says...
Christian McArdle wrote:

The important thing is to own some binoculars. Every couple of months,
or immediately after a storm, go outside and examine the tiles with the
binoculars.

And immediately after any fall of wind-driven powder snow, get up in the
loft with the wet vac - quick, before it melts into the insulation. Same
applies to horizontal gale-driven rain - oh dear, too late for the vac
anyway.

That is what prompted us to get the felting job done, several years
ago... and the general muck that was always blowing in... and the wasps'
nests... and the bats. It totally transformed the loft into a civilised,
dry storage space.

If I had bats in the roof space I wouldn't do anything to disturb
them - they're protected by legislation anyway.