Can cellulose be put in between concrete and plaster ceiling space?

weikee,

actually - you can easily move the cellulose to access any pipes you might need to. just put the flakes back afterwards. been there done that. it's a bit messy but not a huge issue. it does help if you know where to look for the cables and such. if your electriction (or plumber) did a proper layout to beginn with it's not much of a hassle.

ballasts are a problem - if their under the insulation they can get too hot and will blow.

if you have a leakage your ceiling also will have issues. the cellulose should however not get moldy cause it *should* be treated. the one from TCL is. some el-cheapo flakes from china might just not be properly done. afterall even though you essentially place old newspaper in the roof it's not that simple

Us, au, even japan have code to follow and they enforcer it very tight. You should see their workmanship especially japan. I handled my previous company tokyo office relocation. I can you,  their new complete empty office block before renovation is near perfect, the floor, roof, finishing is dam perfect. Even much better than our contractor here after renovation.

over here as long can work is ok.