I live in a 2 story city row house in Philadelphia that is over 100 years old with a flat roof. The space between the second floor ceiling and roof grades down from the front to back - 36 inches or so to 0 when they meets in the rear. The top floor has 3 bedrooms and a bathroom. I already did the front and middle bedrooms, however I did not do any insulating in the ceiling space for those two rooms and regret it now and I am not willing to tear down the finished ceilings.

So now that I am doing the third bedroom, I want to insulate. My first thought is to pull down the lathe and plaster ceiling, put a few inches of rigid foam board between the rafters, some faced fiberglass batts between the ceiling joists(they are not always 16 OC * advise please) and the put the drywall ceiling up. Is it worth all the effort since the 2 other ceilings are not insulated at all?

I know there is the blow in loose stuff, but not sure someone can fit in in that space. I heard that some people have contractors cut holes in the roof and shoot it in from the top, but is that inviting issues?

If the cutting in the flat roof isn't a big deal should I have it done to the entire roof? Can it be the closed cell foam to make it all air tight?

Or should I carry on and come back to the other two ceilings later, most likely blow in from above. Is it ok to have 2 different insulation schemas under the same roof?

I know I am being indecisive but I want to do the right thing now that I have the chance.

  • I see 5 question marks. The first question is subjective as a matter of opinion. The second is broad and unclear. The third is subjective. The answer to the fourth is 'yes'. The fifth is subjective. As we're not a discussion forum, you'll need to revise again to ask a single question (or several closely related questions) that has an objectively correct answer.
    – isherwood
    Commented Jan 25, 2019 at 17:34
  • Don't get me wrong--many of us want to help. The post just doesn't fit our format very well as it is, so it's difficult to answer accurately. Learn more
    – isherwood
    Commented Jan 25, 2019 at 17:38
  • Understood. Seems like I should just patch up the ceiling and have the closed cell sprayed in or find a little person to spray some loose fill in the cock loft and air tighten the rooms from within?
    – ecco88
    Commented Jan 25, 2019 at 17:52
  • Old buildings don't often need vapor barriers, especially if the walls haven't been modernized anyway. Unless you have seen issues with moisture, I'd just blow in the cellulose. Foam would be great but would probably cost 3-5 times as much.
    – isherwood
    Commented Jan 25, 2019 at 17:55
  • @isherwood What’s different about “older buildings don’t often need vapor barriers”?
    – Lee Sam
    Commented Jan 25, 2019 at 19:28

1 Answer 1


I would hire a contractor to blow it in from the inside. They drill a hole and fill the area of each bay They also do this in walls. I would never punch a bunch of holes in my roof that is asking for problems especially in your climate.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.