closed cell foam insulation?

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Brook Johnson

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Hello, I am considering installing closed cell insulation panels between the studs inside the walls of my 80 year old house. The plaster board is off and the siding is in good shape (redwood V-lap) I don't want to take the siding off as I did a thorough restoration on it last year. The vapor retarder (between the studs and the siding) is very old and starting to deteroiorate so I don't want to use fiberglass batts or cellulose as they can hold moisture. I would also use spray foam to seal the gaps and joints. I will then shear wall and sheet rock the walls. I live in Berkeley, CA where the climate is fairly moderate but my fear is that I might end up trapping moisture in there. Any advice on this would be much appreciated!
 

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Brook Johnson

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Welcome.

I would use product similar to this, as a reinforcement for the deteriorating wrap; Henry® 181 Black Asphalt Saturated Glass Fabric
Thanks for the suggestion. If I were pulling the siding off I would most likely use that. My dilemma is that it needs to be installed from the inside of the walls which I have heard is a bad idea and would be almost impossible to seal correctly. That's why I'm thinking closed cell rigid foam between the studs which would hopefully serve as an insulator and a vapor barrier as long as I seal the gaps
 

billshack

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you can use fiberglass pink insulation and the install 6 mil plastic vapor barrier on top of it .
 

Snoonyb

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Thanks for the suggestion. If I were pulling the siding off I would most likely use that. My dilemma is that it needs to be installed from the inside of the walls which I have heard is a bad idea and would be almost impossible to seal correctly. That's why I'm thinking closed cell rigid foam between the studs which would hopefully serve as an insulator and a vapor barrier as long as I seal the gaps
The reason I suggested it was that I used it on the open stud bays, for about 10yrs, to renew the asphalt paper that is an integral base for stucco, to prevent subsequent water intrusion. It's self adhesive.
 

bud16415

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I have done what you are suggesting and I selected the thickness so there would be a little air space between the wood and the foam keeping the foam flush to the studs on the inside. Cut the widths careful and where you go around wires and stuff fill with great stuff spray foam. The end result is the same as if you had it sprayed but better you are letting the wood alone.
 

ctviggen

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That might also give you a slight R value rise. The info I looked at for Dow Thermax said about an extra R value of around 1.8 for 1 inch of air gap, I believe. Though this has an R value of 0.87/inch for an air gap:

R-Values of Materials: Table of Insulation R-Values and Properties for Various Insulation Materials & Building Materials (brick, block, wood, soil, air gaps, etc)

But Dow Thermax is also foil wrapped, so maybe that makes a difference?

What is the vapor permeance of the foam board you're using, though? You can dry to the inside or the outside. If you're using foam board with a low vapor permeance, then you wouldn't be able to dry to the inside anyway, unless the air gap allows that, which I doubt if everything is air sealed. Why not just maximize insulation in that case?

The R value for poly iso is about 6.5 per inch, so you'd get about an R of 4 extra by filling one inch instead of leaving an air gap.
 

Brook Johnson

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Thanks for that info. I finally decided on the 1" closed cell foam board in the stud bays. (Foamular 150) I attached 3/4"×3/4" vertical wood strips to all the studs where the meet the siding. That gives me a 3/4" air gap between the foam and the exterior wall. Each piece of foam boaed is cut 1/2" under size so I have a 1/4" gap on all four sides of each piece which I will fill with Great Stuff, a closed cell spray foam. The biggest challenge now is re-running all the romex and sealing the outlet boxes before I shearwall it. Hard to say what the final R value will be but it should be adequate.
 
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I’ve spent literally days trying to understand the best way to insulate my 115 year old building. Its is a much colder and more humid climate than yours. I think that you did this the right way. Thanks for posting.
 

tomtheelder2020

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Brook,

I don't have any suggestions for your issue - but hope you can help with mine. My 70 y.o. house (in Dixon, not that far east from you) also has redwood V-lap siding that I got started restoring this past summer and will finnish when the weather warms up. The primary issues I have faced are galvanized nails that have rusted out, deteriorating the wood around them, and blistering paint. After removing nails and bad wood I filled the holes with epoxy and drove a corosion resistant screw topped with more epoxy. I don't want to sand after scraping the blistered paint, because of lead-based primer. Initially I was rebuilding a smooth surface using Dap fast-dry caulk (see link below) but was leary of what is essentially a skim coat. I switched to applying several coats of high-build primer (Kel-Bond Ultra) applied with a putty knife so only the low spots are filled. If you can suggest any tips, techniques or lessons learned from your restoration I will appreciate them. Thanks!
 

Brook Johnson

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Hi Tim, I would recommend removing the paint but taking the necessary steps to control the dust. I took mine down to bare wood despite having reservations about it at first. Here is what I did:
Throughly clean the concrete footing so that tape will stick to it.
Lay 6 mil plastic on the ground and let it come up around the footing a few inches.
Use Gorilla tape to seal it to the footing.
Lay sheets of plywood on the plastic so there is no chance of puncturing it with ladders. scaffolding, etc.
Rent or buy some rolling scaffolding and wrap the outside and ends with 6 mil plastic (use clear plastic otherwise it will get hot and dark in there)
I bought mine used from a scaffolding company for about $300
Now you have a sealed space that you can roll back and forth a long your wall. Use a shop vac with a heppa filter and get a hose attachment for your sanders.
You will need to clean the vacum often. Bag the dust with heavy trash bags, seal with tape and label "lead paint dust"
When you're finished take it to your county's household hazardous waste station.
Also, wear a Tyvec suit, goggles and a good respirator.
 

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