Insulating with two ceilings
Hi,
I am in northern NJ. I would like to insulate the uninsulated ceiling in my kitchen. It is the only part of the house that extends out of the house.
The kitchen back in the day had plaster and lath walls and ceiling. Over the years, drywall was installed on the walls and the ceiling
So the kitchen has two ceilings. First ceiling is 3/8 inch drywall with 16 inches on center and then there is 1 foot space and then there’s the plaster ceiling. The kitchen roof like the rest of the house has flat roof. It shares some 1ft open space with the attached living room.
I was thinking of having it insulated with fiberglass insulation by cutting open a 2 feet wide row of sheetrock perpendicular to the studs that are holding on the drywall. Then sliding in the fiberglass in each of the 14 inches of studs and putting the sheetrock back in place with screws and putting compound on it.
I am afraid of getting condensation this way. Will adding insulation cause condensation if it’s already not causing any?
Any suggestions or feedback would be appreciated.
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Replies
Michael,
It will be easier to blow in cellulose than it will be to install fiberglass batts. For more information, see these two articles:
"How to Install Cellulose Insulation"
"Borrowing a Cellulose Blower From a Big Box Store"
With any kind of insulation job, you need to verify that your ceiling has no air leaks before you begin installing the insulation. Your house sounds a little tricky -- you also need to verify that the existing air barriers are uninterrupted and continuous, without any bypasses through hidden air pathways.
Hi Martin,
I don't have any recessed lights or any way for warm air to pass through to the second ceiling once the drywall and compound are put back in place again. It would be sealed up pretty tight. Now if there are any current outside air leaks between the first and second ceiling or from the second ceiling, I am not sure about those.
Thanks for your reply.
If you are creating an unvented roof assembly, then review this:
https://www.buildingscience.com/documents/insights/bsi-043-dont-be-dense
But others claim it will be OK with dense pack cellulose, a smart retarder and excellent air sealing.
If you are creating a vented flat roof, then you have some other challenges.
https://www.greenbuildingadvisor.com/article/insulating-low-slope-residential-roofs
The only way to know just how airtight your ceiling is: conduct a blower door test. Without testing, insulating an unvented roof assembly in just about any climate is risky.
Peter