To insulate or not - moisture related

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Old 12-18-09, 05:10 AM
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To insulate or not - moisture related

I have removed the plywood paneling that made up my interior walls. There is no insulation in the exterior walls, and on the outside there is only 1x8 siding boards. People suggested to me that I not put insulation in the walls because of the risk for moisture to set in and cause mold. Is this likely to happen, or if the siding is caulked well, is it ok to throw fiberglass insulation in there.

If not fiberglass, what about spray foam, and what is the average cost these days of that?
 
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Old 12-18-09, 05:13 AM
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Are you saying that you have no exterior sheathing? It's the wood studs and then the siding on the outside?
 
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Old 12-18-09, 06:05 AM
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Yes, i have 1x8s, for the most part, as my siding. The old stuff is a little thinner. That is nailed directly to the studs. There is no sheathing. However, the house was built in 1839 so the studs are actual 4x4s with big 4x8(maybe 4x6) cross beams in the bottom corners. The plaster inside was removed years ago and replaced with 1/4" plywood, which i have since taken out.
 
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Old 12-18-09, 06:35 AM
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I always have difficulty making recommendations for mixed climates. There just doesn't seem to be a good place to put a vapor barrier. The default is to insure a good air seal as that will slow the transport of moisture in both directions. For your situation, a flash and batt installation would air seal and insulate. The only drawback would be the foam applied to the siding would make future replacement of that siding very difficult, in the least, requiring new foam.

A flash is a thin application of foam, usually 1" is the thinnest they can get. It insulates and seals at the same time. No idea what costs are in your area. $1.00 per board foot is low in some areas and high in others. Once the cavity is air sealed, then a fill with fiberglass can add insulation. No air sealing, and the fg is almost not there.

Another option would be 1" of pink or blue with no plastic or foil on them, sealed between the studs and then filled with unfaced fiberglass or other. The 1' would be a vapor retarder which would allow some drying in either direction. Sealed in place it would also eliminate the air movement and would stay put if siding were replaced in the future.

My 2 cents,
Bud
 
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Old 12-23-09, 04:30 AM
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Thanks Bud!

Sorry for the slow response, we had a ton of rain last friday and it showed me just how much water was getting in through the siding, so i spent the weekend replacing siding and caulking like crazy!

What is the pink or blue you're talking about?
 
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Old 12-23-09, 04:45 AM
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The pink and blue are the rigid foam boards you see at the big box and lumber yards. Without a foil or plastic covering, they will pass some moisture vapor, which can be beneficial in allowing a wall to dry to the outdise. The process is so slow, that occasional moisture on the outside is not a problem.

Yes, siding is generally not intended to be the moisture barrier, it simply acts like an umbrella, shedding most of the rain, but relying on a water barrier underneath, something like Tyvek or felt paper.

Did you add a layer of sheathing?

Bud
 
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Old 12-23-09, 05:59 AM
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no, i did not add any sheathing because i was only replacing siding in spots. a large portion of the siding was replaced a few years ago on one side before I purchased the house but they just put (unsecured) white, foil faced, styrofoam boards inbetween a few studs and called it "new insulation added" on the listing.

The main water penetration is coming from the windows. They just took two sashes, nailed them together, built a cheap fram around them and slapped them in the wall without proper framing. Also, the old siding they did replace was a different thickness so they made up for it by using wood filler and that has since not held up. They also nailed the siding on the top and bottom so the bottom nails are letting water in some places. I've caulked all this now and the original boards do let a little water bleed through, but not so much that it drips down them to other boards. They just saturate a little. I'll try to post some pictures later.
 
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Old 12-29-09, 08:23 PM
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Sorry, i can't figure out how to post attachments on here. but I did post some on the same subject matter i have going on another forum...
To insulate or not - Page 2 - DIY Chatroom - DIY Home Improvement Forum
 
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