# Vapor barrier problems



## Windows on Wash (Aug 30, 2011)

Type of siding, current sheathing, housewrap, location, etc.


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## begal (Jul 23, 2014)

Hi yes it's got 1" of foam and vinyl siding, very wet and cold here.


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## Windows on Wash (Aug 30, 2011)

If the exterior has foam and was done properly, I am going to guess the moisture is coming from the home. What area of the home was this in?


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## begal (Jul 23, 2014)

That's caused by some water damage in the front of the house, that leaked and rotted out. The concrete and old wood absorb moisture from the air and then drys out. I think before their was no VB inside the house so the wood would dry inward. Now it is sandwiched, 1" foam on the exterior is creating a VB.



"
Heiser writes about a house near Buffalo, N.Y., that is ready for drywall. She describes the exterior wall assembly as follows: vinyl siding, 1 in. of rigid polyisocyanurate foam, 1 in. of sprayed closed-cell foam, fiberglass batts, and, finally, clear plastic.
"I'm thinking [the plastic] has to go," she writes. "What are our options? Is it possible to vent the plastic with strategic slits in the plastic?"


Senior editor Martin Holladay has suggested before that exterior foam will prevent condensation, says one anonymous poster, so doesn't this mean the poly can stay?
"No, wrong," replies Dan Kolbert, a builder in Portland, Maine. "There's always moisture somewhere, and it has to escape either inward or outward or it will rot things out (sometimes with remarkable speed)."
And it's no little bit of moisture we're talking about, adds Robert Riversong."


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## Windows on Wash (Aug 30, 2011)

If the wall construction and depth is more than 2x4, 1" foam is not enough to stave off condensation in a cold environment.


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## Gary in WA (Mar 11, 2009)

Yes, you need top remove the rotten/wet wood pieces as they are not still exposed on the inside nor outside. Originally built, with the ends exposed less than 1", they would be able to dry to the interior/exterior, even with the poly you now installed on the interior. But now since 1" of foam board was added/replaced on top of the cement plaster (which alone- promotes mold/restricted drying) -- to restrict drying even more.

Good you removed the plaster, but replacing the foamboard may hinder the drying unless high-permanence low-density 1/2# EPS compared to XPS. The poly now requires the wall to dry to the exterior, giving you twice the risk for mold if water leakage/poly gaps occur. Did you foam around any electrical outlets/switches at the drywall? Caulk/tape it to the floor? Tape any laps/holes air-tight?

Yes-- the damp smell is permeating the Roxul, bring that products smell along with. 

Yes, section by section would work if able to tie them together at the top plates to resist wind/seismic loads properly for your area.

The big problem; "I'm thinking take the siding off and the 1" foam and put a new plywood exterior wall with 1" gap *which would lead to the sofit vents* conveniently.
Do you think this will work?"------- *NO.* Leaving the rainscreen open to the attic will deposit the moisture on the wood roof framing. Very easily over-loading your passive attic ventilation system to grow mold, as you mentioned in recent posting. BTW, if a weak bleach solution (best for a smooth surface cleaner) doesn't get all the mold, you should get a store-bought one without bleach in make-up as it is ineffective on wood fibers, especially DF beams or old lumber that was not surface-milled and has rough surfaces.http://ir.library.oregonstate.edu/x...ff.Forestry.AbilityBleachOther.pdf?sequence=1

The wall should be vented/mesh screened against bugs at top/bottom to be most effective. The attic should get the supply from outside air, never from behind a loose-clad vinyl wall. Vinyl makers sometime use small holes, spaced to far apart to facilitate water drainage in the design so they hold liquid water until it drains/evaporates away. Good you have a rainscreen.

IMO, remove the vinyl/foam, numbering siding pieces to replace easily, remove ANY cord-wood that is dark/wet or shows signs of dried mold, as any future wetting can reactivate mold growth. Block the top of your rainscreen cavity with solid wood/caulk/sealant to the soffit. Use EPS rather than XPS because you don't want to restrict drying on exterior side (only side) of wall to dry.

Some help for others new to cord-wood construction; https://en.wikipedia.org/wiki/Cordwood_construction

Gary


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