A bit unsettling for your daughter, and a pity that she has to cover her windows to avoid it. Now that his view has been obstructed he probably won't do it again, but if he does your daughter could try photographing him each time as evidence if she wants to report it.
When we were first married the man opposite us (about 45-50) liked to stand naked at his open bedroom window and call out to attract anyone in the street, especially women and young girls. You can guess what he did! This happened almost every week, usually when the kids were walking home from school. The police said they'd have to 'catch him in the act', and of course they were never there. Several local Mums grouped together and waited for him to 'perform' and videoed him, he revelled in the attention. A few days later police removed him, he was away for months and then 'rehoused' elsewhere. His mother continued to live there for a few years until she died. She once said he was always a peculiar boy. For years afterwards that house was called 'the w---ers house' by the locals, a bit unfortunate for the subsequent occupiers!