Plaster ceiling vs drywall and sound insulation

[Matt Nunnink]

Hi all,

After a long time being on the sidelines and researching, I am finally closing on a 2 family in Jan 2026. The property is a very well built 1920s colonial. I've owned one of the same era before (single family) which I gutted and fully refitted everything in the house. At the time I used fiberglass insulation in the interior walls for sound proofing because I had purchased a bit extra. I was pretty impressed how well it did - but I also did take the time to caulk all the trim and seal up any major gaps in the framing.

For this rental property I intend to live there while I renovate both floors and convert the attic to extra living space. My plan is to start at the bottom and work upward because I need to run some plumbing and wiring up.

Question to the more experienced people here. I don't need to gut this property since the wiring has already been upgraded. The majority of the plaster is still in place, including the ceiling on the first floor. Does anyone have real life experience comparing the sound deadening properties of lath and plaster ceilings vs drywall with some form of sound insulation (like rockwool)? I plan to add recessed lighting and considered three options:

1. Rip the ceiling down, add new work recessed lighting boxes and rockwool + seal any accessible air gaps / fire blocking if I can access it in the walls (balloon framed).

2. Cut holes and try to use pop in recessed lighting (have to see if this works with lath - it may be hard to do).

3. if #2 works, possibly try blown in cellulose or spray foam in the ceiling after adding the lights. 

Curious if anyone has some experience with this. 

[Kevin Sobilo]

Quote from @Matt Nunnink:

@Kevin Sobilo that is a good idea. I would imagine that plus the 3" sound insulation would make a huge difference 

Yes, rockwool insulation especially is very good for sound and pretty good to work with.