Insulating a pre-existing suspended bathroom ceiling

[retrography]

The previous owner of my house has redone the bathrooms and toilets pretty well, with nicely finished suspended ceilings and downlights.

What he didn’t take care of properly was insulation. The space between the suspended ceiling and the real ceiling is not well-insulated from the roof, which means in winter there is strong draft and even wind in that area, making toilets and bathroom some of the coldest rooms in the house.

I have found a way to block the major air inlets into the ceiling’s “crawl space”, which will kill the wind issue. But for the draft not to happen I need to insulate above the suspended ceiling somehow without tearing it apart.

I was thinking of blowing in some polystyrene beads through the downlight holes, and then seal those holes off when reinstalling the lights. The risk is that styrofoam will react with the plastic cable shields (e.g., for lights, fan, etc.) and create short-circuit/fire hazard.

Now my questions:

1. Is there any better way to insulate this space apart from polystyrene beads, short of completely tearing out the ceiling?
2. Are there any other risk associated with styrofoam beads used for this purpose?
3. How can I protect the in-ceiling cables in order to mitigate the reaction risk?

P.S.: Note that the toilets and the bathrooms are otherwise efficiently ventilated and heated with automatic humidity and temperature-based activation.

 

[JohnD]

The space between the suspended ceiling and the real ceiling is not well-insulated from the roof,

Insulate from the roof space.

 

[retrography]

I would, if I could. The breach between the roof space and the ceiling space is internal to the structure and very wide. It can only be mended when completely redoing the roof.

This is a centennial house. Everything is made to “breath”, sometimes for the right and sometimes for the wrong reasons.