Insulating above third story

[Danmcg]

Hey everyone, my first post here. I have an 1842 brick house in NJ. The third floor is a finished attic (finished in the 19th century) and is in pretty bad shape. Flat ceiling with knee walls, all plaster, much of which is failing. I have lived here for 8 years and have been thinking about renovating this space from day one. The big question is how to insulate. The roof structure is a frame, rafters 24” spaced, purlins nailed to rafters, original cedar shakes nailed to purlins. Overtop of the original cedar roof is an old standing seam metal roof. No roof ventilation whatsoever. As it stands, the third story does not seem to have any moisture problems. I’ve never seen evidence of such in 8 years. To make this space more usable, insulating would be smart, it does get chilly in the winter and hot in the summer. I must say I’m more interested in historic preservation than modernizing. I’d like to find a way to insulate this space well enough to improve the conditions in extreme temperatures, but in a non invasive way. I understand the rafters can’t be traditionally insulated without roof venting. One solution is to gut the room and spray foam everything. Im not crazy about that idea. I don’t care about energy efficiency. I’d like to know if I can insulate with wool batts above the flat ceiling, but leave the underside of the roof, as well as the knee walls, un-insulated. That way most of the plaster can be restored, and I can mitigate heat loss through the ceiling. The space is piped for heat and there are radiators, but I’ve turned the valves off for them. I’m fairly certain the space was occupied as recently as the 70s (based on carpet, wood paneling, Pink Floyd stickers, etc). Would like to hear anyone’s thoughts!

[Gothichome]

Hello and welcome Banncg. I see no reason why you can’t insulate above the ceiling. If I am reading your scenario correctly there must be a bit of an attic space. I think the best way maybe to make some sort of lattice arrangement on the ceiling joist lay a vapour barrier down and place the fibreglass bats on top of the vapour barrier.
Tel us more of your home and pictures, we really like pictures here in the district.
Ron

[phil]

are the rafters 2x4 or 2x6 or?
You might consider ISO board, more R value and I think you might be able to place them between the rafters allowing airspace for the roof to cool.

If the roof runs hot the roofing life is reduced but you have a metal roof so it might not be as important, I doubt a metl roof would "care"
but in summer if you can let the heat out before it penetrates into the living space it may be cooler.

mine is 2x4 and the roof is sheeted with the wood strips that used to hold the shingles still intact. I have some fiberglass pink between, Its not really well insulated. behind my little walls I put roxul in the floor and doors for access and painted plywood to cover the insulation , nothing against the roof. that is not living space it's storage .

I think if I had it all open I;d use the ISO board with the tin foil up and leave a gap for air then it could have a ridge vent after, maybe. you can instead use the corregated styrofoam stuff that is sold for that. I used the ISO board in my living room walls and cut them wiht a handsaw a little loose then filled each end near the stud with spray foam , those walls are tight. Id do that again.
Id use roxul if you need a sound barrier or there are other things. I used some soundproof drywall in my living room walls. I'm in a noisy area.

plaster vs drywall. we can look at both sides of that.. depends how original you want to be.
mine had 70's panelling replaced by 1/2" drywall , it wasn't plastered because it wasn't occupied space originally. I have some rather steep steps going up as a result of some mods done long ago. Its a bit hot in summer and insulation could be better but it's livable it's basically the master bedroom.
when the ceiling was drywalled I hired a couple of bozos and we agreed to remove the strapping which was below the joist. they did not do as agreed and threw on the drywall anyway and it lost a little ceiling height and maybe gained airflow but If I knew what I know now I woud have done it a bit different. I had some closets up there and re drywalled them. I have a second room that is U shaped and has nice light but an awkward shape. what Id do now is keep it all open so it had light from both ends.. too late to change all that.

I replaced my roof , used fibergass structural shingles. I added roof vents, about 6 the holes are about 6x8 or so roughly. one will be for a bathroom fan. if you research or ask a roofer there is a formula of square inches of vent to square footage

solar panels are coming down and getting more reasonable maybe that's a thing of the not too distant future. my prediction is that solar panels will eventually "be the roof" instead of being on top of the roof. Id leave your standing seam tin roof alone if you can it should last a long time.

welcome to the forum !

[Danmcg]

I’m really quite interested in Havelock Wool for insulation. I think I’ll contact them to ask if their product would be suitable for my application. I like either that or mineral wool. I try to stay natural and limit chemicals as much as possible. And I’ll admit I’m a bit of a purist. I prefer lath and plaster whenever possible. I try my best to restore and preserve the original characteristics of the house as much as I can. I’ve researched roof venting and insulation for years and understand the importance in maintaining a dry roof. But I’ve also read quite a bit about how old houses are a bit different. There’s so much inherent air flow and cracks and crevices, modern building technology somewhat doesn’t apply in many cases. My opinion is, if my home has maintained its original roof structure for the past 180 years, somethings working. And maybe insulating will alter that in a negative way. If I use a reversible insulation method (flat laying havelock or mineral wool above ceiling) and keep a trap door in the ceiling to access the attic space, I can keep an eye on it and monitor the humidity and condition throughout my time here. And if it turns out insulating was a big mistake, I can pull it all out again.

Having some cosmetic issues with my metal roof right now and I’m waiting on an estimate to have it recoated. Took me quite a while to find someone familiar with the product I want used on the roof (Acrymax). I’m worried the cost will be high, we got a few estimates on pulling the roof off and installing shingles and it’s pretty reasonable. Problem is, the red metal roof is a hugely attractive element of my home. It wouldn’t be the same without it.

I’m new here and am planning on getting around to posting on the introduction page, posting photos and such. Just extremely busy and haven’t had the time!

At the moment I’m researching lath and plaster restoration. Limeworks makes ready-to-mix lime products that seem historically accurate. All the jargon and specifics are a bit confusing to the layman though. I think I’ll give them a call, explain my situation and get their advice on the exact products I need.

[Gothichome]

You sound just like most of here in the district, preserving, restoring and maintaining in a period manner. The old home world could use more folks like us here.
As far as insulation, we just had blown insulation right onto the plaster ceiling in the attic. It has given us no issues going on eight years now. The insulation is just recycled paper chopped up really fine and treaded with a fire and moisture so it will not absorb moisture and will not turn into a big fire ball. I think both treatments are needed to meet code for insulation.
Moisture build up is not an issue do to the the natural breath ability of plaster.
I look forward to pictures and reading about your progress.
Ron