Old Wall New Insulation


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Old 07-16-15, 11:46 AM
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Old Wall New Insulation

Hi
I am renovating my old semidetached house, and recently took out the vinyl siding at the front to restore the redwood underneath.
Plan being to replace the insulation that was exterior, with interior.

I am about to remove the drywall in one of the rooms and I was hoping to maximize the insulation I add to the exterior wall:
Currently it only has vapor paper.
I want to install either Ruxol or fiberglass and would prefer faced, but I understand that given the vapor barrier, I should not install faced and go with unfaced. What are your opinions about it?
Given I am restoring the wood and no newer insulation is being installed on the outside, what other ways can I fortify the inside with?
Can I install rigid foam as well over the vapor paper (within the joists) before I put in the fiberglass? If I do that, should I tape it to the joists to maximize airflow 0? What type of tape? And would there be a moisture issue between the vapor paper and the rigid foam?
Alternatively, should I put fiberglass or wool batts and then rigid foam before I drywall? In that case, should I tape it or would that create a moisture sandwich?
Or is there another way all together from the interior?
Thank you for reading
 
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Old 07-16-15, 11:56 AM
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Hi Mia and welcome to the forum.
I'm busy, just came in for a short break but will pick this up later today. Others will be along as well.
A question. CA is one of those states that has many climates. Can you narrow down yours. Do you heat and AC or just ac? The difference is, in very hot climates with ac only the vapor barrier goes to the outside. Mixed climates may not need a vapor barrier. Newer recommendations usually refer to "vapor diffusion retarders" and even paint may will fall into one of those categories.

I'll be back,
Bud
 
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Old 07-16-15, 01:41 PM
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I force air heat only. No AC.
I live on the cooler area of SF, on top of a hill that sees a lot of fog action. The back of the house had to be clad with new Hardie to resist the Pacific cold winds so although the front doesn't get the direct hit, we are a rather cold area.
I live in Ingleside. The experimental hole on the sheetrock shows brown paper if that helps.
 
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Old 07-16-15, 04:17 PM
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It would be useful to know how your wall is constructed. The redwood underneath the vinyl siding, is that clapboard or something else? Is there sheathing behind the redwood?
 
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Old 07-16-15, 06:40 PM
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Back again. As Droo asked, I'm also having a little difficulty following the construction of the wall and exactly what you will be removing and replacing.

The current recommendation for vapor barriers is "yes" in the far (cold) north and "yes" in the deep south. Sounds like you are inbetween so one is not absolutely necessary. The necessary detail however is air sealing. Air flow will move a lot of moisture. The moisture that moves through drywall and building materials is minimal and slow, thus it is able to dry before it does any harm.

If your siding under that vinyl siding was installed directly against the studs, no sheathing, then your exterior is very open to air flow into those cavities. I'll wait to hear more about how this is constructed.

Bud
 
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Old 07-16-15, 08:44 PM
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Hi thank you for your welcoming messages btw

To clarify:
Vinyl (already removed)
Rustic Vee Redwood in excellent condition (to our pleasant surprise)
Seething in the form of planks (not full plywood-the house was built in 1951)
Vapor Paper
Studs and air (no internal insulation)
Drywall

Next step is: I am removing drywall to install internal insulation and removing K&T (with electrician) etc

So I am looking to optimize the insulation on the exterior wall.
On the adjoined wall with the neighbors I am already doing acoustic drywall and Green Glue along with unfaced R-21

Thank you
 
  #7  
Old 07-17-15, 05:51 AM
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The only reason I would add a vapor barrier to the inside would be to improve the air sealing, given the more open nature of your siding. I would use Roxul and cover with a plastic vapor barrier. Faced high density fiberglass would be my second choice, but acceptable,

Caulk (fire rated) all unused holes and around electrical and plumbing. Flash and caulk larger holes. With an adjoining wall, sound reduction improves with air sealing.

Bud
 
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Old 07-18-15, 08:08 AM
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K&T in a 1951 building? Are you sure about that?
 
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Old 07-18-15, 11:31 AM
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My in-laws lived in a house built around that time and it most definitely had knob and tube wiring. It may, however, have been that way because the house was built by an old timer for his own use about the time he retired. At any rate, K&T was a perfectly acceptable wiring method at least into the 1960s.
 
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Old 07-19-15, 09:00 AM
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Thank you Bud!

K&T yes. The house I bought is part of 30+ house built at the same time in 1951, all the same. The K&t is actually in very good condition, main problem had been not allowing insulation and a few suicious splices from previous owner which made it an easy decision to bring up to code.
 
 

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