Replies

1. 
   MadisonRenovations | Jan 29, 2009 08:08am | #1

   No plastic sheet. That was meant to prevent moist air migration, which you've done with the foam. Let things air out on the inside. You might want to consider breaking the thermal bridge of the studs, since you went ahead with the foam. I cross-strapped with 1x3's. You could instead add some foam board on the studs.

   ---mike...

   Madison Renovations
   Cambridge, Mass.

1. 
   Rehabhog | Jan 29, 2009 04:47pm | #3

   Thanks Mike,

                    I'll be removing the film I've installed. It didn't seem right and it's still easy to remove at this point. I'm happy to say that thermal bridges are at least one thing I don't have to worry about. The metal studs are a full 9" from the exterior sheeting. Along with the foam, this leaves a full 6''of space for dense packed cellulose with only the sill(?) as the point of contact between the inside wall and the exterior siding.

   Thanks again

   Rehab.Knowledge: So hard to acquire but often given away freely... Beautiful.

2. 
   DickRussell | Jan 29, 2009 04:26pm | #2

   A couple of questions that others would quickly have asked anyway:

   Where is the house (climate-wise)? Fill in some profile info for yourself. Climate info comes first, because answers are very climate-specific.

   What kind of spray foam went into the wall cavity - open or closed cell foam?

   What is outside the cavity for sheathing, wrap, and siding?

   Are the windows properly installed/flashed/integrated with the wrap?

   Why is the basement humid?

   Now some thoughts to consider. If the wall cavity foam is open-cell (sometimes call "half-pound foam"), then it is vapor permeable, and (for a cold climate) an inside vapor retarder is needed. I wouldn't recommend poly film for this. If you use a film VR, I'd suggest Certainteed's MemBrain, because it gets more permeable when the humidity next to it goes up, allowing drying to the inside.

   You could just use a vapor-retardant primer paint over the drywall. That, too, would allow drying to the inside.

   If there might be leakage of rain around the windows, if not properly flashed, then some water can get to the framing at times, and it should be able to dry to either inside or outside. In winter, this may well have to be to the inside.

   If the cavity foam is closed-cell, then it constitutes a vapor retarder as well as air-sealer. Not only don't you need the VR film under the drywall, you should leave it out, so that moisture passing through the wood framing can dry to the inside.

   You might think about doing something for that humid basement. Depending on what the source of moisture is, there are different ways to address it. However, even if you foam under the floor above it, there still is wood framing that can absorb moisture, and having this in a tightened up house might present a problem.

   Others certainly will be along with more questions and suggestions, maybe even while I've been typing. Edit: geez, I didn't even see Mike's reply before I typed.

   
   

   ---

   Edited 1/29/2009 8:28 am ET by DickRussell

1. 
   Rehabhog | Jan 29, 2009 05:22pm | #4

   Hello,

            never taught about the profile, I'll be filling it in shortly. I think the spray is closed cell. The salesman pitch was that it block everything out. Windows are circa 1830's and there is no house wrap. Windows and flashing are to be replaced but between now and then, water could come in.

   I'll be taking down the film I've installed. In this particular application it seemed questionable.

   As for the basement. Its stone walls and earth floor make it a cold, humid and dark place. It will never be a comfortable room or even a good mechanical room ( rust, access, low ceiling). These negatives are, however, big positives  for root and wine cellars but I'm still working on the details...

   Thanks for the good advice

   RehabKnowledge: So hard to acquire but often given away freely... Beautiful.

1. 
   DickRussell | Jan 29, 2009 05:52pm | #5

   I was thinking again about the humidity in the cellar and your earlier statement that the floor above the cellar would be foamed. If that foam were to be closed cell, you'd have a substantial vapor retarder in place, leaving the humidity nowhere to go. Then I have to wonder if the humidity down there would build up to a point where you'd have mold and eventually rot on the exposed wood framing.I think it was sometime last year that Fine Homebuilding (or was it JLC?) had an article on how the folks at Building Science (Joe and Betsy) rehabbed an older building. They addressed the issue of moisture in the basement with a combination of foam on the walls and poly over the floor, as I recall.

1. 
   Rehabhog | Jan 29, 2009 06:19pm | #6

   Hi M. Russell,

                     I'm still researching the cellar construction ( will look into mentioned article). I've got a few books that explain what you suggest about sealing off humidity but oddly I'm worried this might not give me enough humidity for an efficient root and wine cellar.

   I don't know if it will fly, I still have to order some books, but the main plan right now is to:

    cover anything that isn't stone with foam in the cellar,

     install vents with gates at different grades

   and cover the walls and foam sprayed ceiling with a lime mortar (which as anti fungal properties).

   Please feel free to point out any short comings in this plan.

   Thank you for the interest,

   Rehab.

    

    Knowledge: So hard to acquire but often given away freely... Beautiful.

1. 
   Piffin | Jan 29, 2009 06:26pm | #7

   You did say polyurethene spray foam, That IS closed cell and a VB already. 

    

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