Quick background: house is a cape cod 1 1/2 story brick, built 1939, attic was built in I'm guessing mid-late 40's. The attic floors are oak strip over subfloor, there appears to be rockwool batts (paper side up) in the joists between the attic floor and ceiling below. Knee walls are about 6 ft tall, then, about 2 ft of angle, then a flat ceiling. The areas outboard of the kneewalls are all accessible for storage and have sub floor over the aforementioned rockwool batts. The roof is original painted metal shingles. House is in coastal Georgia.

Problem: The roof rafters were all packed some time ago with rockwool batts from gutter to peak, retained by chicken wire and, in some cases covered with cardboard, presumably to keep from getting dusted with the rockwool when moving about in the storage areas. There is no insulation in the knee walls, nor is there any in the ceiling joists. I'd like to insulate it properly but since its all finished with no access to anything above the knee walls, I wonder if its worth removing all that rock wool? It seems to have not suffered any ill effects moisture-wise over the past 50? years, other than rodent burrowing here & there. Can I leave the rafter insulation in place and perhaps have the ceiling insulation blown in? I've already started putting fiberglass batts on the outside of the kneewalls. There appears to be plenty of ventilation in the storage spaces but I can't vouch for the areas above the ceilings.

Thanks.

 

Id ask first this insulation down in the floor or the ceiling joist paper side up. Take and look at it again. They use to make insulation with a paper on both sides it had like a tar on the paper on one side and on the other side of the insulation was just paper. You want to have the paper with the tar on it down on the ceiling below.

Lets go this way. From the out side wall or over hang of the home to the knee wall insulation paper side down. Up the knee wall paper side to face the room. That short angle of the ceiling paper side down to the room but you have to have extruded foam rafter vents there. Then some kind of V/B down on the room ceiling before you blow insulation in. also you need some good vents up there in the roof for this part of the attic. I dont see how the insulation up in the roof rafters is still good or Id look at the wood up there on that roof and see if it is still good. You are thinking right moisture could have got in there for sure. You could take like an ice pick and see how soft the roof wood is.
ED

 

Hello Ed,
Thank you for the quick reply. I've gone back and checked, the between floors insulation is, indeed, paper on 1 side only and, although I've only pulled up a limited number of sub-floor boards, the paper side is on top. John's manville made it, they tell me its faced rockwool (no asbestos). I presume the stuff in the rafters is also asbestos free. (Short of having it tested, is there an easy way to tell)?

So here's where I think I stand: Faced rockwool over the heated areas needs to come out and get replaced with a more modern product, VB towards the downstairs living area. Remove all the rockwool in the rafters (fun ). I did find out that 2 out of 4 gable ends have vents above the ceiling proper, no other vents in the roof. Then, cut some kind of access through the ceilings to lay a proper VB and insulate the top surface of the attic ceilings. I also want to make sure there is flow through ventilation across the tops of the ceiling and make sure the anglewalls above the kneewalls are letting air past the insulation to help ventilate the upper regions.

The hard part is the VB in the ceiling as there is very little headroom at that point. I imagine it will be hard to just lay sheet plastic due to the wiring, odd joist/rafter layout, chimney, etc. Any recommendations? I figure it would be almost impossible to jockey around rolls of pink stuff to lay out. It seems that a properly painted ceiling would suffice for a VB, is this not the case?
Many thanks.

 

You could check with a paint store there. There are some paints out that they say or for and work some what as a V/B . So if you go for a blow insulation look into this for the ceiling there . Make sure air can get up and over that slope in the ceiling. ED