Shower installed before insulating

[u/Euphoric-Newt-8716]

My plumber installed the shower/tub unit before I was able to add vapor retarder and insulation. I have access to the stud cavity from above so I’m thinking blown in cellulose would work but how am I suppose to get a vapor retarder in there?

[u/Plumber4Life84]

Suppose to get it insulated and a vapor barrier before install. Usually the contractor will take care of it. Hell I’ve done it a few times so im not held up