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Insulation installation plan any good?

SerpentDragonZX | Posted in Green Building Techniques on

My question, or plan as I should say, is about an insulation package I’m planning. Some details…
House built in 1947. Mostly original, rough sawn, material are true measurements which attributes to some ‘character’ in some places. House has some settled areas, but has good bones. Wood seems to be Hemlock based on what others have told me if it matters, and it’s hard as nails. Siding is aluminum with what appears to be styrofoam backing. Exterior siding sheathing including roof sheathing is just plain boards it seems that you can easily see between each. After I bought the house, starting to see lots of odd situations the builders of old created. Haha.
Anyways, I’m not exactly a pro carpenter, but I do know some basics, and learn quickly. I can watch or read a guide or manual, get rhythm of what to do fairly easily. I try to research everything as much as possible before attempting something usually, and that’s where this comes into play…
After completely gutting my upstairs bedroom, determined to originally just replace with hardwood flooring, then ended up to fix the electrical and drywall problems, came across extensive insulation, electrical, air sealing, water problems… One thing led to another, and apparently I opened up quite the can of worms. They say you don’t really see underlying problems till you been living in a house at least a year, but I’m glad I tore everything out to bare framing. The upstairs consists of 2 bedrooms with vaulted ceilings and knee walls, which I think was originally just a very large attic, one bedroom of which currently my daughters have, so I skipped the other for now. Attempting 1 side at a time. Aside from all other problems I’m tackling (and there is a lot) I am looking for any suggestions of the insulation packages I’m wanting to do, but unsure if they are problem causing for later. I figure I better go 110% into this, because insulation wise, I believe this is the most important aspect of it in the entire house. It’s worth the little bit extra money then traditional I think. I’m going this route because I don’t trust the spray foam, it can trap moisture (better suited to newer homes), it’s more expensive by about double, and atleast this way, it’s not permanently stuck there.
The Roof Line/Vaulted Wall
From the outside in, I will fasten 1″ strips of wood to the inside roof, side of rafters, not the roof sheathing (read further if you see why I’m stating this obvious thing). I will put foil faced 1″ EPS R-Tech foam paneling to ride the 1″ spacing I created, creating an air baffle for the roof to breathe while also creating a thermal break (EPS because it doesn’t change its R-value over time or from temps like Polyiso or XPS and can breathe better). Foil facing out towards roof creating a radiant barrier as well in the air baffle channel, cause it gets ridiculously hot upstairs in summer, and the foil needs an air gap to work anyways. Unsure if I’m supposed to remove the clear plastic on the other side of foam panels, since I can’t find anything very specific about it, other then I’m thinking it’s used during the process in making them. Below this, I will put Rockwool mineral wool to fill the cavity, as much as I can against the foam board, without packing tight. Then after this, I will simply put traditional poly sheeting, 8 mils thick. I’ll only be able to collectively get about roughly R24, but with the added foil, it could potentially be a lot higher at certain times of the year when its reflecting radiant heat and this is mainly being treated as a wall, not attic, until it gets to the actual ceiling as well. Seems quite low, but originally… it was completely uninsulated on both knee walls, and floors beyond the knee walls which is also my ceiling of the first floor bedroom (mine). No soffets. No baffles. There was roughly 2 layers of faced insulation stapled directly to the roof boards and rafters, wet and disintegrated. Wet under both window sills, leaks when rains super heavy. So anything, I mean ANYTHING I do will be better. Just an empty, framed room stripped and gutted is already warmer in my house believe it or not and I live in New England. Eventually, I will put up new knee walls and I will insulate those as well, to slow heat loss/buildup further and added sound dampening. EPS Foam blocking will be installed around the rim joist, and floor will be laid with mineral wool. The knee wall space will also have OSB installed all around and be wrapped in a radiant barrier on all sides, minus the floor, to make up some difference in the insulation not being as thick later. This all might be overkill, but it’s cheap insurance to me. Under each new baffle I create, I will either drill a “2 hole for vent inserts (I know, it’s a lot), or just remove the existing board outside, and just install a continuous soffet vent providing there is room. The baffle package will lead up to the gable vent area (later to be removed and just replaced with a ridgevent), which will have it’s own insulation package in the ceiling. This complete package will end to roughly the level of the bottom of the gable end vents or level with the top of the ceiling insulation package.
The Ceiling:
I will raise the current collar ties by adding 2X4’s on top of each one with an additional layer of 2×6’s atop those but spaced about 1″ apart using ripped down blocks as spacers, and as I go, remove the current 2X4’s. This will effectively raise the ceiling 4″ (the current height is a tad too low for the ceiling fans installed by last owner which are definitely needed, along with the floor being lowered roughly about 1/2″ because of 2 layered subflooring and extreme slopes and valleys which I’m currently fixing to be in plane with better levelness). The 2X6’s atop enable them to act as floor joists for a crawl space as well. The ceiling cavities from the inside out, will be filled with mineral wool insulation, then 1/4″ fanfold foam sheets laid across the tops of the then now ceiling joists as a thermal break, and capped with OSB board creating a small crawl space in case of needed use of storage, emergencies such as a possible leaks, chimney inspection, electrical, etc… This space will also get wrapped, on all sides with radiant barrier as well later. Should be able to achieve about an R46 in the ceiling/attic crawl space. Again, 8 mil poly will be installed before sheetrock.
As much stuff I have researched and checked, I’m sure there are flaws I just didn’t think of, missed, or completely overlooked. I guess I’m looking more for acceptance and experienced insight of my plan before attacking it.

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  1. Expert Member
    Zephyr7 | | #1

    I think you’re over thinking some of this. What you propose is going to be LOT of labor with all the details. Can you provide some drawings of what you’re planning and maybe some pics of what you’re starting with? This will help everyone here to better understand what you need to do.

    My first thought is that you should NOT be putting in a layer of poly too. Unless your local codes require it, that poly vapor barrier more of a problem than a solution.


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