Should SKY pay for the damage?

i had my sky t.v recently updated, the installler however left a piece of equiupment that he removed for the dish to replace on the chimney which somehow fell weeks later and damaged the windscreen of my car badly it will need to be replaced, he should never of left anything on the roof and it was rather heavy. ive emailed sky again and again with no reply, what can i do i need to get the windscreen fixed should they have to pay? my car insurance dosent cover windscreen repair