Residing an uninsulated home

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  #1  
Old 01-08-18, 09:04 AM
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Residing an uninsulated home

Hi,


I am in Zone 7 and have a 120 year old home. We are preparing to meet with the contractor to finalize details on our residing and trim capping project and I wanted to get insight from you all.

The house will be stripped of cedar, tar paper and old lap to reveal diagonal wood planking. Interior walls are uninsulated lathe & plaster with the exception of an addition (bathroom made in the 60's) which is drywall.

We are trying to stay behind the window trim but think some form of insulation would be prudent for an air barrier.

Layer 1: Obdyke Slicker HP Rainscreen
www.benjaminobdyke.com/products/slicker-hp-rainscreen-6-mm/
Layer 2: 7/16" Smartside Lap siding
https://lpcorp.com/products/siding/l...cts/lap-siding


So, what kind of insulation and where can we incorporate into our building envelope to supplement or replace our current setup?

Many thanks in advance.

Bridgette
 
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Old 01-08-18, 10:23 AM
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Hi bridgettesd and welcome to the forum.

Does the "diagonal wood planking" serve as the framing or are there studs as well?

In Zone 7 you have some rather tough insulation requirements but final values are set by your local authority. Your contractor should have those details.

One approach when the outside has been stripped is to add several inches of rigid foam. It is also a good time to install new windows as you can use the new construction style with nail flanges and proper flashing.

There are guidelines for how much rigid is needed when being installed on the outside to avoid condensation issues. I see that link now requires a membership but here is the one line that you need: " R-10 for 2x4 walls; R-15 for 2x6 walls"
Here is the link and they have a free 30 day trial membership:
Calculating the Minimum Thickness of Rigid Foam Sheathing | GreenBuildingAdvisor.com

Strange, the second attempt did not run into the required membership, who knows?

There are also some links of "how to" when adding rigid foam to the exterior.

Bud
 
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Old 01-08-18, 11:57 AM
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Hi Bud,
I forgot to mention that we are keeping the existing trim as it would be cost prohibitive to tear it all out. They are planning to wrap the trim in aluminum and I believe we then have a thickness limitation.

Therefore we plan to just use vinyl replacement and contractor with wrap aluminum under the tyvek.

I did a little more research and am leaning toward a 1.5" R5 Roxul comfortboard over tyvek with 1x3" strapping on top, then the lap siding. The wall breathe like crazy!
 
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Old 01-08-18, 04:38 PM
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Not sure what your local codes require, but with a major renovation I would expect you would be required to bring the insulation levels up to minimum code. And I'm not sure they care how difficult that will be. I'm guessing but R-20 for the walls would be the least I would expect.

Are you getting permits and having inspections? If so and you are planning anything less than code be sure to get approval in advance in writing. It is awfully expensive to tear out good work and start over.

Bud
 
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Old 01-09-18, 04:51 AM
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You want to install insulation in the external wall cavities that provide the highest R value. Some, like rigid foam board or roll fiberglass, are best installed by exposing the framing members. A factor that may limit your options is the thickness of the current framing. Modern home construction framing is usually 2x4 or 2x6 on 16 inch centers so the common insulating materials are sized to fit these dimensions. Others, like spray foam or blown material can be done without removing the current sheathing. Framing size is not an issue. Hope this helps.
 
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Old 01-09-18, 07:35 PM
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Hello @bridgittesd.
I have a similar question as was asked by @Bud9051. What is the function of the diagonal planking? I'm having a difficult time picturing that.
At first you mentioned Benjamin Obdyke's rain screen, then you were referring to Tyvek. What is your current choice?
You also mentioned that you want/need to keep your current trim and you also mentioned Roxul's Comfortboard. I am a fan of Roxul, but wouldn't the Comfortboard push the cladding out proud of the trim?

Maybe you could post some pictures that could help us visualize what you are dealing with. How did you know you have diagonal planks? If it is visible anywhere, it would be great to see a picture of that. Also a picture of the trim.

Thanks and good luck with your project. It sounds like a lot of work, but fun and rewarding.
 
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Old 01-10-18, 04:17 AM
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You do not say what state you are in but where I believe you live it is a requirement to have an approved vapor barrier on the warm side of your wall and ceiling insulation.
Some types of rigid foam insulation are moisture resistant but do not qualify as a vapor barrier.
Have you allowed for this?

In areas I an familiar with a 2 part spray foam insulation if 2 inches thick are an approved method.
It is a relatively easy way of adding a vapor barrier to an old structure but is somewhat costly.
 
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Old 01-15-18, 03:41 AM
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Q: Are you getting permits and having inspections? If so and you are planning anything less than code be sure to get approval in advance in writing. It is awfully expensive to tear out good work and start over.

A: Wasn't planning on it unless the contractor is.

Q: Diagonal planking

A: it's 1"x 12" with 1" gaps

Going with dense pack cellulose in 4" deep cavity, mento 1000 wrb, roxul comfortboard 1.5", 1*4 furring strips 16" OC, Smartside 7/16" lap siding, innie flashed replacement windows.

Rvalue reqs say 21 and are found here:

https://energycode.pnl.gov/EnergyCodeReqs/

I have got 16 in walls and 5 outside = 21!!
 
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Old 01-16-18, 12:23 PM
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@bridgettesd, it sounds like you are researching the project well and selecting good materials. If your contractor has good references and you've seen his/her work, then, combined with the quality materials, you are probably in good shape.

Thanks for providing the picture. That does help.
What is the location of the area you photographed? Specifically, I'm wondering what the flat surface is at the bottom of the picture. I'm asking because it looks like there is some rot at the bottom of the diagonal board on the lower left. Make sure that proper water/moisture management is planned for that area.
Also, it looks like some "stuff" (maybe insulation) is already in the wall. Will that interfere with the cellulose?

I'd still like to see a picture of a window. I'm not sure how you're going to accomplish an "innie" window with trim coil over the trim--especially since it sounds like the Roxul Comfortboard will be proud of the trim.

Lastly, is it safe to assume that you're removing all of the old cedar?
 
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