We did that years ago on our first home. There was a crawl space up there, so my husband was able to get in there with the blower to see what he was doing. We sold the house about 5 years ago. Last year we got an email from the buyers with photos of a collapsed ceiling. Apparently, a leak had developed in the roof which they had neglected to fix (or didn’t notice) and the insulation got wet and heavy and….Fix your roof first!
Anyway, here’s a link for you. It’ll explain it better than I could.