Insulating flat roof on 100-year-old brick row house
My recently purchased 100 yr old row house (in NYC – total 1200 sq ft), sandwiched between 2 party walls, recently had its roof redone – prior to purchase. One of the next door neighbors confirmed the roof installation was a “warm roof” (foam panel install over the ply substrate w/ weatherproof barrier). There are a couple of old vents/holes thru the tops of the brick walls (with screen) at the top of the front & back of the house (presumably to vent what would have been a “cold roof” construction back in the day).
The question is, now that its a “warm roof” should we still install insulation between the ceiling joists of the second floor (the ceilings below the warm roof)?
There would still be an air gap from below the roof substrate to the top of the ceiling joists. The wood roof structure was built with a slope providing a large gap above the ceiling joists at the front of the house and a lesser gap at the back of the house (although still more than a few inches above the joist tops). Again, presumably because construction was for a “cold roof”.
Is there any advice against installing Mineral Wool (rockwool) insulation between the ceiling joists there to help keep cooling and heating from escaping through sheetrock out through the vent holes and out the brick walls?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part